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alistair23-linux/block/bfq-iosched.c

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/*
* Budget Fair Queueing (BFQ) I/O scheduler.
*
* Based on ideas and code from CFQ:
* Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
*
* Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
* Paolo Valente <paolo.valente@unimore.it>
*
* Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
* Arianna Avanzini <avanzini@google.com>
*
* Copyright (C) 2017 Paolo Valente <paolo.valente@linaro.org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* BFQ is a proportional-share I/O scheduler, with some extra
* low-latency capabilities. BFQ also supports full hierarchical
* scheduling through cgroups. Next paragraphs provide an introduction
* on BFQ inner workings. Details on BFQ benefits, usage and
* limitations can be found in Documentation/block/bfq-iosched.txt.
*
* BFQ is a proportional-share storage-I/O scheduling algorithm based
* on the slice-by-slice service scheme of CFQ. But BFQ assigns
* budgets, measured in number of sectors, to processes instead of
* time slices. The device is not granted to the in-service process
* for a given time slice, but until it has exhausted its assigned
* budget. This change from the time to the service domain enables BFQ
* to distribute the device throughput among processes as desired,
* without any distortion due to throughput fluctuations, or to device
* internal queueing. BFQ uses an ad hoc internal scheduler, called
* B-WF2Q+, to schedule processes according to their budgets. More
* precisely, BFQ schedules queues associated with processes. Each
* process/queue is assigned a user-configurable weight, and B-WF2Q+
* guarantees that each queue receives a fraction of the throughput
* proportional to its weight. Thanks to the accurate policy of
* B-WF2Q+, BFQ can afford to assign high budgets to I/O-bound
* processes issuing sequential requests (to boost the throughput),
* and yet guarantee a low latency to interactive and soft real-time
* applications.
*
* In particular, to provide these low-latency guarantees, BFQ
* explicitly privileges the I/O of two classes of time-sensitive
* applications: interactive and soft real-time. This feature enables
* BFQ to provide applications in these classes with a very low
* latency. Finally, BFQ also features additional heuristics for
* preserving both a low latency and a high throughput on NCQ-capable,
* rotational or flash-based devices, and to get the job done quickly
* for applications consisting in many I/O-bound processes.
*
* BFQ is described in [1], where also a reference to the initial, more
* theoretical paper on BFQ can be found. The interested reader can find
* in the latter paper full details on the main algorithm, as well as
* formulas of the guarantees and formal proofs of all the properties.
* With respect to the version of BFQ presented in these papers, this
* implementation adds a few more heuristics, such as the one that
* guarantees a low latency to soft real-time applications, and a
* hierarchical extension based on H-WF2Q+.
*
* B-WF2Q+ is based on WF2Q+, which is described in [2], together with
* H-WF2Q+, while the augmented tree used here to implement B-WF2Q+
* with O(log N) complexity derives from the one introduced with EEVDF
* in [3].
*
* [1] P. Valente, A. Avanzini, "Evolution of the BFQ Storage I/O
* Scheduler", Proceedings of the First Workshop on Mobile System
* Technologies (MST-2015), May 2015.
* http://algogroup.unimore.it/people/paolo/disk_sched/mst-2015.pdf
*
* [2] Jon C.R. Bennett and H. Zhang, "Hierarchical Packet Fair Queueing
* Algorithms", IEEE/ACM Transactions on Networking, 5(5):675-689,
* Oct 1997.
*
* http://www.cs.cmu.edu/~hzhang/papers/TON-97-Oct.ps.gz
*
* [3] I. Stoica and H. Abdel-Wahab, "Earliest Eligible Virtual Deadline
* First: A Flexible and Accurate Mechanism for Proportional Share
* Resource Allocation", technical report.
*
* http://www.cs.berkeley.edu/~istoica/papers/eevdf-tr-95.pdf
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/cgroup.h>
#include <linux/elevator.h>
#include <linux/ktime.h>
#include <linux/rbtree.h>
#include <linux/ioprio.h>
#include <linux/sbitmap.h>
#include <linux/delay.h>
#include "blk.h"
#include "blk-mq.h"
#include "blk-mq-tag.h"
#include "blk-mq-sched.h"
#include <linux/blktrace_api.h>
#include <linux/hrtimer.h>
#include <linux/blk-cgroup.h>
#define BFQ_IOPRIO_CLASSES 3
#define BFQ_CL_IDLE_TIMEOUT (HZ/5)
#define BFQ_MIN_WEIGHT 1
#define BFQ_MAX_WEIGHT 1000
#define BFQ_WEIGHT_CONVERSION_COEFF 10
#define BFQ_DEFAULT_QUEUE_IOPRIO 4
#define BFQ_WEIGHT_LEGACY_DFL 100
#define BFQ_DEFAULT_GRP_IOPRIO 0
#define BFQ_DEFAULT_GRP_CLASS IOPRIO_CLASS_BE
/*
* Soft real-time applications are extremely more latency sensitive
* than interactive ones. Over-raise the weight of the former to
* privilege them against the latter.
*/
#define BFQ_SOFTRT_WEIGHT_FACTOR 100
struct bfq_entity;
/**
* struct bfq_service_tree - per ioprio_class service tree.
*
* Each service tree represents a B-WF2Q+ scheduler on its own. Each
* ioprio_class has its own independent scheduler, and so its own
* bfq_service_tree. All the fields are protected by the queue lock
* of the containing bfqd.
*/
struct bfq_service_tree {
/* tree for active entities (i.e., those backlogged) */
struct rb_root active;
/* tree for idle entities (i.e., not backlogged, with V <= F_i)*/
struct rb_root idle;
/* idle entity with minimum F_i */
struct bfq_entity *first_idle;
/* idle entity with maximum F_i */
struct bfq_entity *last_idle;
/* scheduler virtual time */
u64 vtime;
/* scheduler weight sum; active and idle entities contribute to it */
unsigned long wsum;
};
/**
* struct bfq_sched_data - multi-class scheduler.
*
* bfq_sched_data is the basic scheduler queue. It supports three
* ioprio_classes, and can be used either as a toplevel queue or as an
* intermediate queue on a hierarchical setup. @next_in_service
* points to the active entity of the sched_data service trees that
* will be scheduled next. It is used to reduce the number of steps
* needed for each hierarchical-schedule update.
*
* The supported ioprio_classes are the same as in CFQ, in descending
* priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE.
* Requests from higher priority queues are served before all the
* requests from lower priority queues; among requests of the same
* queue requests are served according to B-WF2Q+.
* All the fields are protected by the queue lock of the containing bfqd.
*/
struct bfq_sched_data {
/* entity in service */
struct bfq_entity *in_service_entity;
/* head-of-line entity (see comments above) */
struct bfq_entity *next_in_service;
/* array of service trees, one per ioprio_class */
struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES];
/* last time CLASS_IDLE was served */
unsigned long bfq_class_idle_last_service;
};
/**
* struct bfq_weight_counter - counter of the number of all active entities
* with a given weight.
*/
struct bfq_weight_counter {
unsigned int weight; /* weight of the entities this counter refers to */
unsigned int num_active; /* nr of active entities with this weight */
/*
* Weights tree member (see bfq_data's @queue_weights_tree and
* @group_weights_tree)
*/
struct rb_node weights_node;
};
/**
* struct bfq_entity - schedulable entity.
*
* A bfq_entity is used to represent either a bfq_queue (leaf node in the
* cgroup hierarchy) or a bfq_group into the upper level scheduler. Each
* entity belongs to the sched_data of the parent group in the cgroup
* hierarchy. Non-leaf entities have also their own sched_data, stored
* in @my_sched_data.
*
* Each entity stores independently its priority values; this would
* allow different weights on different devices, but this
* functionality is not exported to userspace by now. Priorities and
* weights are updated lazily, first storing the new values into the
* new_* fields, then setting the @prio_changed flag. As soon as
* there is a transition in the entity state that allows the priority
* update to take place the effective and the requested priority
* values are synchronized.
*
* Unless cgroups are used, the weight value is calculated from the
* ioprio to export the same interface as CFQ. When dealing with
* ``well-behaved'' queues (i.e., queues that do not spend too much
* time to consume their budget and have true sequential behavior, and
* when there are no external factors breaking anticipation) the
* relative weights at each level of the cgroups hierarchy should be
* guaranteed. All the fields are protected by the queue lock of the
* containing bfqd.
*/
struct bfq_entity {
/* service_tree member */
struct rb_node rb_node;
/* pointer to the weight counter associated with this entity */
struct bfq_weight_counter *weight_counter;
/*
* Flag, true if the entity is on a tree (either the active or
* the idle one of its service_tree) or is in service.
*/
bool on_st;
/* B-WF2Q+ start and finish timestamps [sectors/weight] */
u64 start, finish;
/* tree the entity is enqueued into; %NULL if not on a tree */
struct rb_root *tree;
/*
* minimum start time of the (active) subtree rooted at this
* entity; used for O(log N) lookups into active trees
*/
u64 min_start;
/* amount of service received during the last service slot */
int service;
/* budget, used also to calculate F_i: F_i = S_i + @budget / @weight */
int budget;
/* weight of the queue */
int weight;
/* next weight if a change is in progress */
int new_weight;
/* original weight, used to implement weight boosting */
int orig_weight;
/* parent entity, for hierarchical scheduling */
struct bfq_entity *parent;
/*
* For non-leaf nodes in the hierarchy, the associated
* scheduler queue, %NULL on leaf nodes.
*/
struct bfq_sched_data *my_sched_data;
/* the scheduler queue this entity belongs to */
struct bfq_sched_data *sched_data;
/* flag, set to request a weight, ioprio or ioprio_class change */
int prio_changed;
};
struct bfq_group;
/**
* struct bfq_ttime - per process thinktime stats.
*/
struct bfq_ttime {
/* completion time of the last request */
u64 last_end_request;
/* total process thinktime */
u64 ttime_total;
/* number of thinktime samples */
unsigned long ttime_samples;
/* average process thinktime */
u64 ttime_mean;
};
/**
* struct bfq_queue - leaf schedulable entity.
*
* A bfq_queue is a leaf request queue; it can be associated with an
* io_context or more, if it is async or shared between cooperating
* processes. @cgroup holds a reference to the cgroup, to be sure that it
* does not disappear while a bfqq still references it (mostly to avoid
* races between request issuing and task migration followed by cgroup
* destruction).
* All the fields are protected by the queue lock of the containing bfqd.
*/
struct bfq_queue {
/* reference counter */
int ref;
/* parent bfq_data */
struct bfq_data *bfqd;
/* current ioprio and ioprio class */
unsigned short ioprio, ioprio_class;
/* next ioprio and ioprio class if a change is in progress */
unsigned short new_ioprio, new_ioprio_class;
/*
* Shared bfq_queue if queue is cooperating with one or more
* other queues.
*/
struct bfq_queue *new_bfqq;
/* request-position tree member (see bfq_group's @rq_pos_tree) */
struct rb_node pos_node;
/* request-position tree root (see bfq_group's @rq_pos_tree) */
struct rb_root *pos_root;
/* sorted list of pending requests */
struct rb_root sort_list;
/* if fifo isn't expired, next request to serve */
struct request *next_rq;
/* number of sync and async requests queued */
int queued[2];
/* number of requests currently allocated */
int allocated;
/* number of pending metadata requests */
int meta_pending;
/* fifo list of requests in sort_list */
struct list_head fifo;
/* entity representing this queue in the scheduler */
struct bfq_entity entity;
/* maximum budget allowed from the feedback mechanism */
int max_budget;
/* budget expiration (in jiffies) */
unsigned long budget_timeout;
/* number of requests on the dispatch list or inside driver */
int dispatched;
/* status flags */
unsigned long flags;
/* node for active/idle bfqq list inside parent bfqd */
struct list_head bfqq_list;
/* associated @bfq_ttime struct */
struct bfq_ttime ttime;
/* bit vector: a 1 for each seeky requests in history */
u32 seek_history;
/* node for the device's burst list */
struct hlist_node burst_list_node;
/* position of the last request enqueued */
sector_t last_request_pos;
/* Number of consecutive pairs of request completion and
* arrival, such that the queue becomes idle after the
* completion, but the next request arrives within an idle
* time slice; used only if the queue's IO_bound flag has been
* cleared.
*/
unsigned int requests_within_timer;
/* pid of the process owning the queue, used for logging purposes */
pid_t pid;
/*
* Pointer to the bfq_io_cq owning the bfq_queue, set to %NULL
* if the queue is shared.
*/
struct bfq_io_cq *bic;
/* current maximum weight-raising time for this queue */
unsigned long wr_cur_max_time;
/*
* Minimum time instant such that, only if a new request is
* enqueued after this time instant in an idle @bfq_queue with
* no outstanding requests, then the task associated with the
* queue it is deemed as soft real-time (see the comments on
* the function bfq_bfqq_softrt_next_start())
*/
unsigned long soft_rt_next_start;
/*
* Start time of the current weight-raising period if
* the @bfq-queue is being weight-raised, otherwise
* finish time of the last weight-raising period.
*/
unsigned long last_wr_start_finish;
/* factor by which the weight of this queue is multiplied */
unsigned int wr_coeff;
/*
* Time of the last transition of the @bfq_queue from idle to
* backlogged.
*/
unsigned long last_idle_bklogged;
/*
* Cumulative service received from the @bfq_queue since the
* last transition from idle to backlogged.
*/
unsigned long service_from_backlogged;
/*
* Value of wr start time when switching to soft rt
*/
unsigned long wr_start_at_switch_to_srt;
unsigned long split_time; /* time of last split */
};
/**
* struct bfq_io_cq - per (request_queue, io_context) structure.
*/
struct bfq_io_cq {
/* associated io_cq structure */
struct io_cq icq; /* must be the first member */
/* array of two process queues, the sync and the async */
struct bfq_queue *bfqq[2];
/* per (request_queue, blkcg) ioprio */
int ioprio;
#ifdef CONFIG_BFQ_GROUP_IOSCHED
uint64_t blkcg_serial_nr; /* the current blkcg serial */
#endif
/*
* Snapshot of the idle window before merging; taken to
* remember this value while the queue is merged, so as to be
* able to restore it in case of split.
*/
bool saved_idle_window;
/*
* Same purpose as the previous two fields for the I/O bound
* classification of a queue.
*/
bool saved_IO_bound;
/*
* Same purpose as the previous fields for the value of the
* field keeping the queue's belonging to a large burst
*/
bool saved_in_large_burst;
/*
* True if the queue belonged to a burst list before its merge
* with another cooperating queue.
*/
bool was_in_burst_list;
/*
* Similar to previous fields: save wr information.
*/
unsigned long saved_wr_coeff;
unsigned long saved_last_wr_start_finish;
unsigned long saved_wr_start_at_switch_to_srt;
unsigned int saved_wr_cur_max_time;
struct bfq_ttime saved_ttime;
};
enum bfq_device_speed {
BFQ_BFQD_FAST,
BFQ_BFQD_SLOW,
};
/**
* struct bfq_data - per-device data structure.
*
* All the fields are protected by @lock.
*/
struct bfq_data {
/* device request queue */
struct request_queue *queue;
/* dispatch queue */
struct list_head dispatch;
/* root bfq_group for the device */
struct bfq_group *root_group;
/*
* rbtree of weight counters of @bfq_queues, sorted by
* weight. Used to keep track of whether all @bfq_queues have
* the same weight. The tree contains one counter for each
* distinct weight associated to some active and not
* weight-raised @bfq_queue (see the comments to the functions
* bfq_weights_tree_[add|remove] for further details).
*/
struct rb_root queue_weights_tree;
/*
* rbtree of non-queue @bfq_entity weight counters, sorted by
* weight. Used to keep track of whether all @bfq_groups have
* the same weight. The tree contains one counter for each
* distinct weight associated to some active @bfq_group (see
* the comments to the functions bfq_weights_tree_[add|remove]
* for further details).
*/
struct rb_root group_weights_tree;
/*
* Number of bfq_queues containing requests (including the
* queue in service, even if it is idling).
*/
int busy_queues;
/* number of weight-raised busy @bfq_queues */
int wr_busy_queues;
/* number of queued requests */
int queued;
/* number of requests dispatched and waiting for completion */
int rq_in_driver;
/*
* Maximum number of requests in driver in the last
* @hw_tag_samples completed requests.
*/
int max_rq_in_driver;
/* number of samples used to calculate hw_tag */
int hw_tag_samples;
/* flag set to one if the driver is showing a queueing behavior */
int hw_tag;
/* number of budgets assigned */
int budgets_assigned;
/*
* Timer set when idling (waiting) for the next request from
* the queue in service.
*/
struct hrtimer idle_slice_timer;
/* bfq_queue in service */
struct bfq_queue *in_service_queue;
/* bfq_io_cq (bic) associated with the @in_service_queue */
struct bfq_io_cq *in_service_bic;
/* on-disk position of the last served request */
sector_t last_position;
/* time of last request completion (ns) */
u64 last_completion;
/* time of first rq dispatch in current observation interval (ns) */
u64 first_dispatch;
/* time of last rq dispatch in current observation interval (ns) */
u64 last_dispatch;
/* beginning of the last budget */
ktime_t last_budget_start;
/* beginning of the last idle slice */
ktime_t last_idling_start;
/* number of samples in current observation interval */
int peak_rate_samples;
/* num of samples of seq dispatches in current observation interval */
u32 sequential_samples;
/* total num of sectors transferred in current observation interval */
u64 tot_sectors_dispatched;
/* max rq size seen during current observation interval (sectors) */
u32 last_rq_max_size;
/* time elapsed from first dispatch in current observ. interval (us) */
u64 delta_from_first;
/*
* Current estimate of the device peak rate, measured in
* [BFQ_RATE_SHIFT * sectors/usec]. The left-shift by
* BFQ_RATE_SHIFT is performed to increase precision in
* fixed-point calculations.
*/
u32 peak_rate;
/* maximum budget allotted to a bfq_queue before rescheduling */
int bfq_max_budget;
/* list of all the bfq_queues active on the device */
struct list_head active_list;
/* list of all the bfq_queues idle on the device */
struct list_head idle_list;
/*
* Timeout for async/sync requests; when it fires, requests
* are served in fifo order.
*/
u64 bfq_fifo_expire[2];
/* weight of backward seeks wrt forward ones */
unsigned int bfq_back_penalty;
/* maximum allowed backward seek */
unsigned int bfq_back_max;
/* maximum idling time */
u32 bfq_slice_idle;
/* user-configured max budget value (0 for auto-tuning) */
int bfq_user_max_budget;
/*
* Timeout for bfq_queues to consume their budget; used to
* prevent seeky queues from imposing long latencies to
* sequential or quasi-sequential ones (this also implies that
* seeky queues cannot receive guarantees in the service
* domain; after a timeout they are charged for the time they
* have been in service, to preserve fairness among them, but
* without service-domain guarantees).
*/
unsigned int bfq_timeout;
/*
* Number of consecutive requests that must be issued within
* the idle time slice to set again idling to a queue which
* was marked as non-I/O-bound (see the definition of the
* IO_bound flag for further details).
*/
unsigned int bfq_requests_within_timer;
/*
* Force device idling whenever needed to provide accurate
* service guarantees, without caring about throughput
* issues. CAVEAT: this may even increase latencies, in case
* of useless idling for processes that did stop doing I/O.
*/
bool strict_guarantees;
/*
* Last time at which a queue entered the current burst of
* queues being activated shortly after each other; for more
* details about this and the following parameters related to
* a burst of activations, see the comments on the function
* bfq_handle_burst.
*/
unsigned long last_ins_in_burst;
/*
* Reference time interval used to decide whether a queue has
* been activated shortly after @last_ins_in_burst.
*/
unsigned long bfq_burst_interval;
/* number of queues in the current burst of queue activations */
int burst_size;
/* common parent entity for the queues in the burst */
struct bfq_entity *burst_parent_entity;
/* Maximum burst size above which the current queue-activation
* burst is deemed as 'large'.
*/
unsigned long bfq_large_burst_thresh;
/* true if a large queue-activation burst is in progress */
bool large_burst;
/*
* Head of the burst list (as for the above fields, more
* details in the comments on the function bfq_handle_burst).
*/
struct hlist_head burst_list;
/* if set to true, low-latency heuristics are enabled */
bool low_latency;
/*
* Maximum factor by which the weight of a weight-raised queue
* is multiplied.
*/
unsigned int bfq_wr_coeff;
/* maximum duration of a weight-raising period (jiffies) */
unsigned int bfq_wr_max_time;
/* Maximum weight-raising duration for soft real-time processes */
unsigned int bfq_wr_rt_max_time;
/*
* Minimum idle period after which weight-raising may be
* reactivated for a queue (in jiffies).
*/
unsigned int bfq_wr_min_idle_time;
/*
* Minimum period between request arrivals after which
* weight-raising may be reactivated for an already busy async
* queue (in jiffies).
*/
unsigned long bfq_wr_min_inter_arr_async;
/* Max service-rate for a soft real-time queue, in sectors/sec */
unsigned int bfq_wr_max_softrt_rate;
/*
* Cached value of the product R*T, used for computing the
* maximum duration of weight raising automatically.
*/
u64 RT_prod;
/* device-speed class for the low-latency heuristic */
enum bfq_device_speed device_speed;
/* fallback dummy bfqq for extreme OOM conditions */
struct bfq_queue oom_bfqq;
spinlock_t lock;
/*
* bic associated with the task issuing current bio for
* merging. This and the next field are used as a support to
* be able to perform the bic lookup, needed by bio-merge
* functions, before the scheduler lock is taken, and thus
* avoid taking the request-queue lock while the scheduler
* lock is being held.
*/
struct bfq_io_cq *bio_bic;
/* bfqq associated with the task issuing current bio for merging */
struct bfq_queue *bio_bfqq;
/*
* io context to put right after bfqd->lock is released. This
* filed is used to perform put_io_context, when needed, to
* after the scheduler lock has been released, and thus
* prevent an ioc->lock from being possibly taken while the
* scheduler lock is being held.
*/
struct io_context *ioc_to_put;
};
enum bfqq_state_flags {
BFQQF_just_created = 0, /* queue just allocated */
BFQQF_busy, /* has requests or is in service */
BFQQF_wait_request, /* waiting for a request */
BFQQF_non_blocking_wait_rq, /*
* waiting for a request
* without idling the device
*/
BFQQF_fifo_expire, /* FIFO checked in this slice */
BFQQF_idle_window, /* slice idling enabled */
BFQQF_sync, /* synchronous queue */
BFQQF_IO_bound, /*
* bfqq has timed-out at least once
* having consumed at most 2/10 of
* its budget
*/
BFQQF_in_large_burst, /*
* bfqq activated in a large burst,
* see comments to bfq_handle_burst.
*/
BFQQF_softrt_update, /*
* may need softrt-next-start
* update
*/
BFQQF_coop, /* bfqq is shared */
BFQQF_split_coop /* shared bfqq will be split */
};
#define BFQ_BFQQ_FNS(name) \
static void bfq_mark_bfqq_##name(struct bfq_queue *bfqq) \
{ \
__set_bit(BFQQF_##name, &(bfqq)->flags); \
} \
static void bfq_clear_bfqq_##name(struct bfq_queue *bfqq) \
{ \
__clear_bit(BFQQF_##name, &(bfqq)->flags); \
} \
static int bfq_bfqq_##name(const struct bfq_queue *bfqq) \
{ \
return test_bit(BFQQF_##name, &(bfqq)->flags); \
}
BFQ_BFQQ_FNS(just_created);
BFQ_BFQQ_FNS(busy);
BFQ_BFQQ_FNS(wait_request);
BFQ_BFQQ_FNS(non_blocking_wait_rq);
BFQ_BFQQ_FNS(fifo_expire);
BFQ_BFQQ_FNS(idle_window);
BFQ_BFQQ_FNS(sync);
BFQ_BFQQ_FNS(IO_bound);
BFQ_BFQQ_FNS(in_large_burst);
BFQ_BFQQ_FNS(coop);
BFQ_BFQQ_FNS(split_coop);
BFQ_BFQQ_FNS(softrt_update);
#undef BFQ_BFQQ_FNS
/* Logging facilities. */
#ifdef CONFIG_BFQ_GROUP_IOSCHED
static struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
static struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg);
#define bfq_log_bfqq(bfqd, bfqq, fmt, args...) do { \
char __pbuf[128]; \
\
blkg_path(bfqg_to_blkg(bfqq_group(bfqq)), __pbuf, sizeof(__pbuf)); \
blk_add_trace_msg((bfqd)->queue, "bfq%d%c %s " fmt, (bfqq)->pid, \
bfq_bfqq_sync((bfqq)) ? 'S' : 'A', \
__pbuf, ##args); \
} while (0)
#define bfq_log_bfqg(bfqd, bfqg, fmt, args...) do { \
char __pbuf[128]; \
\
blkg_path(bfqg_to_blkg(bfqg), __pbuf, sizeof(__pbuf)); \
blk_add_trace_msg((bfqd)->queue, "%s " fmt, __pbuf, ##args); \
} while (0)
#else /* CONFIG_BFQ_GROUP_IOSCHED */
#define bfq_log_bfqq(bfqd, bfqq, fmt, args...) \
blk_add_trace_msg((bfqd)->queue, "bfq%d%c " fmt, (bfqq)->pid, \
bfq_bfqq_sync((bfqq)) ? 'S' : 'A', \
##args)
#define bfq_log_bfqg(bfqd, bfqg, fmt, args...) do {} while (0)
#endif /* CONFIG_BFQ_GROUP_IOSCHED */
#define bfq_log(bfqd, fmt, args...) \
blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args)
/* Expiration reasons. */
enum bfqq_expiration {
BFQQE_TOO_IDLE = 0, /*
* queue has been idling for
* too long
*/
BFQQE_BUDGET_TIMEOUT, /* budget took too long to be used */
BFQQE_BUDGET_EXHAUSTED, /* budget consumed */
BFQQE_NO_MORE_REQUESTS, /* the queue has no more requests */
BFQQE_PREEMPTED /* preemption in progress */
};
struct bfqg_stats {
#ifdef CONFIG_BFQ_GROUP_IOSCHED
/* number of ios merged */
struct blkg_rwstat merged;
/* total time spent on device in ns, may not be accurate w/ queueing */
struct blkg_rwstat service_time;
/* total time spent waiting in scheduler queue in ns */
struct blkg_rwstat wait_time;
/* number of IOs queued up */
struct blkg_rwstat queued;
/* total disk time and nr sectors dispatched by this group */
struct blkg_stat time;
/* sum of number of ios queued across all samples */
struct blkg_stat avg_queue_size_sum;
/* count of samples taken for average */
struct blkg_stat avg_queue_size_samples;
/* how many times this group has been removed from service tree */
struct blkg_stat dequeue;
/* total time spent waiting for it to be assigned a timeslice. */
struct blkg_stat group_wait_time;
/* time spent idling for this blkcg_gq */
struct blkg_stat idle_time;
/* total time with empty current active q with other requests queued */
struct blkg_stat empty_time;
/* fields after this shouldn't be cleared on stat reset */
uint64_t start_group_wait_time;
uint64_t start_idle_time;
uint64_t start_empty_time;
uint16_t flags;
#endif /* CONFIG_BFQ_GROUP_IOSCHED */
};
#ifdef CONFIG_BFQ_GROUP_IOSCHED
/*
* struct bfq_group_data - per-blkcg storage for the blkio subsystem.
*
* @ps: @blkcg_policy_storage that this structure inherits
* @weight: weight of the bfq_group
*/
struct bfq_group_data {
/* must be the first member */
struct blkcg_policy_data pd;
unsigned int weight;
};
/**
* struct bfq_group - per (device, cgroup) data structure.
* @entity: schedulable entity to insert into the parent group sched_data.
* @sched_data: own sched_data, to contain child entities (they may be
* both bfq_queues and bfq_groups).
* @bfqd: the bfq_data for the device this group acts upon.
* @async_bfqq: array of async queues for all the tasks belonging to
* the group, one queue per ioprio value per ioprio_class,
* except for the idle class that has only one queue.
* @async_idle_bfqq: async queue for the idle class (ioprio is ignored).
* @my_entity: pointer to @entity, %NULL for the toplevel group; used
* to avoid too many special cases during group creation/
* migration.
* @stats: stats for this bfqg.
* @active_entities: number of active entities belonging to the group;
* unused for the root group. Used to know whether there
* are groups with more than one active @bfq_entity
* (see the comments to the function
* bfq_bfqq_may_idle()).
* @rq_pos_tree: rbtree sorted by next_request position, used when
* determining if two or more queues have interleaving
* requests (see bfq_find_close_cooperator()).
*
* Each (device, cgroup) pair has its own bfq_group, i.e., for each cgroup
* there is a set of bfq_groups, each one collecting the lower-level
* entities belonging to the group that are acting on the same device.
*
* Locking works as follows:
* o @bfqd is protected by the queue lock, RCU is used to access it
* from the readers.
* o All the other fields are protected by the @bfqd queue lock.
*/
struct bfq_group {
/* must be the first member */
struct blkg_policy_data pd;
struct bfq_entity entity;
struct bfq_sched_data sched_data;
void *bfqd;
struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
struct bfq_queue *async_idle_bfqq;
struct bfq_entity *my_entity;
int active_entities;
struct rb_root rq_pos_tree;
struct bfqg_stats stats;
};
#else
struct bfq_group {
struct bfq_sched_data sched_data;
struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
struct bfq_queue *async_idle_bfqq;
struct rb_root rq_pos_tree;
};
#endif
static struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
static unsigned int bfq_class_idx(struct bfq_entity *entity)
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
return bfqq ? bfqq->ioprio_class - 1 :
BFQ_DEFAULT_GRP_CLASS - 1;
}
static struct bfq_service_tree *
bfq_entity_service_tree(struct bfq_entity *entity)
{
struct bfq_sched_data *sched_data = entity->sched_data;
unsigned int idx = bfq_class_idx(entity);
return sched_data->service_tree + idx;
}
static struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync)
{
return bic->bfqq[is_sync];
}
static void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq,
bool is_sync)
{
bic->bfqq[is_sync] = bfqq;
}
static struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic)
{
return bic->icq.q->elevator->elevator_data;
}
#ifdef CONFIG_BFQ_GROUP_IOSCHED
static struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq)
{
struct bfq_entity *group_entity = bfqq->entity.parent;
if (!group_entity)
group_entity = &bfqq->bfqd->root_group->entity;
return container_of(group_entity, struct bfq_group, entity);
}
#else
static struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq)
{
return bfqq->bfqd->root_group;
}
#endif
static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio);
static void bfq_put_queue(struct bfq_queue *bfqq);
static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,
struct bio *bio, bool is_sync,
struct bfq_io_cq *bic);
static void bfq_end_wr_async_queues(struct bfq_data *bfqd,
struct bfq_group *bfqg);
static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq);
/* Expiration time of sync (0) and async (1) requests, in ns. */
static const u64 bfq_fifo_expire[2] = { NSEC_PER_SEC / 4, NSEC_PER_SEC / 8 };
/* Maximum backwards seek (magic number lifted from CFQ), in KiB. */
static const int bfq_back_max = 16 * 1024;
/* Penalty of a backwards seek, in number of sectors. */
static const int bfq_back_penalty = 2;
/* Idling period duration, in ns. */
static u64 bfq_slice_idle = NSEC_PER_SEC / 125;
/* Minimum number of assigned budgets for which stats are safe to compute. */
static const int bfq_stats_min_budgets = 194;
/* Default maximum budget values, in sectors and number of requests. */
static const int bfq_default_max_budget = 16 * 1024;
/*
* Async to sync throughput distribution is controlled as follows:
* when an async request is served, the entity is charged the number
* of sectors of the request, multiplied by the factor below
*/
static const int bfq_async_charge_factor = 10;
/* Default timeout values, in jiffies, approximating CFQ defaults. */
static const int bfq_timeout = HZ / 8;
static struct kmem_cache *bfq_pool;
/* Below this threshold (in ns), we consider thinktime immediate. */
#define BFQ_MIN_TT (2 * NSEC_PER_MSEC)
/* hw_tag detection: parallel requests threshold and min samples needed. */
#define BFQ_HW_QUEUE_THRESHOLD 4
#define BFQ_HW_QUEUE_SAMPLES 32
#define BFQQ_SEEK_THR (sector_t)(8 * 100)
#define BFQQ_SECT_THR_NONROT (sector_t)(2 * 32)
#define BFQQ_CLOSE_THR (sector_t)(8 * 1024)
#define BFQQ_SEEKY(bfqq) (hweight32(bfqq->seek_history) > 32/8)
/* Min number of samples required to perform peak-rate update */
#define BFQ_RATE_MIN_SAMPLES 32
/* Min observation time interval required to perform a peak-rate update (ns) */
#define BFQ_RATE_MIN_INTERVAL (300*NSEC_PER_MSEC)
/* Target observation time interval for a peak-rate update (ns) */
#define BFQ_RATE_REF_INTERVAL NSEC_PER_SEC
/* Shift used for peak rate fixed precision calculations. */
#define BFQ_RATE_SHIFT 16
/*
* By default, BFQ computes the duration of the weight raising for
* interactive applications automatically, using the following formula:
* duration = (R / r) * T, where r is the peak rate of the device, and
* R and T are two reference parameters.
* In particular, R is the peak rate of the reference device (see below),
* and T is a reference time: given the systems that are likely to be
* installed on the reference device according to its speed class, T is
* about the maximum time needed, under BFQ and while reading two files in
* parallel, to load typical large applications on these systems.
* In practice, the slower/faster the device at hand is, the more/less it
* takes to load applications with respect to the reference device.
* Accordingly, the longer/shorter BFQ grants weight raising to interactive
* applications.
*
* BFQ uses four different reference pairs (R, T), depending on:
* . whether the device is rotational or non-rotational;
* . whether the device is slow, such as old or portable HDDs, as well as
* SD cards, or fast, such as newer HDDs and SSDs.
*
* The device's speed class is dynamically (re)detected in
* bfq_update_peak_rate() every time the estimated peak rate is updated.
*
* In the following definitions, R_slow[0]/R_fast[0] and
* T_slow[0]/T_fast[0] are the reference values for a slow/fast
* rotational device, whereas R_slow[1]/R_fast[1] and
* T_slow[1]/T_fast[1] are the reference values for a slow/fast
* non-rotational device. Finally, device_speed_thresh are the
* thresholds used to switch between speed classes. The reference
* rates are not the actual peak rates of the devices used as a
* reference, but slightly lower values. The reason for using these
* slightly lower values is that the peak-rate estimator tends to
* yield slightly lower values than the actual peak rate (it can yield
* the actual peak rate only if there is only one process doing I/O,
* and the process does sequential I/O).
*
* Both the reference peak rates and the thresholds are measured in
* sectors/usec, left-shifted by BFQ_RATE_SHIFT.
*/
static int R_slow[2] = {1000, 10700};
static int R_fast[2] = {14000, 33000};
/*
* To improve readability, a conversion function is used to initialize the
* following arrays, which entails that they can be initialized only in a
* function.
*/
static int T_slow[2];
static int T_fast[2];
static int device_speed_thresh[2];
#define BFQ_SERVICE_TREE_INIT ((struct bfq_service_tree) \
{ RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
#define RQ_BIC(rq) ((struct bfq_io_cq *) (rq)->elv.priv[0])
#define RQ_BFQQ(rq) ((rq)->elv.priv[1])
/**
* icq_to_bic - convert iocontext queue structure to bfq_io_cq.
* @icq: the iocontext queue.
*/
static struct bfq_io_cq *icq_to_bic(struct io_cq *icq)
{
/* bic->icq is the first member, %NULL will convert to %NULL */
return container_of(icq, struct bfq_io_cq, icq);
}
/**
* bfq_bic_lookup - search into @ioc a bic associated to @bfqd.
* @bfqd: the lookup key.
* @ioc: the io_context of the process doing I/O.
* @q: the request queue.
*/
static struct bfq_io_cq *bfq_bic_lookup(struct bfq_data *bfqd,
struct io_context *ioc,
struct request_queue *q)
{
if (ioc) {
unsigned long flags;
struct bfq_io_cq *icq;
spin_lock_irqsave(q->queue_lock, flags);
icq = icq_to_bic(ioc_lookup_icq(ioc, q));
spin_unlock_irqrestore(q->queue_lock, flags);
return icq;
}
return NULL;
}
/*
* Scheduler run of queue, if there are requests pending and no one in the
* driver that will restart queueing.
*/
static void bfq_schedule_dispatch(struct bfq_data *bfqd)
{
if (bfqd->queued != 0) {
bfq_log(bfqd, "schedule dispatch");
blk_mq_run_hw_queues(bfqd->queue, true);
}
}
/*
* Next two functions release bfqd->lock and put the io context
* pointed by bfqd->ioc_to_put. This delayed put is used to not risk
* to take an ioc->lock while the scheduler lock is being held.
*/
static void bfq_unlock_put_ioc(struct bfq_data *bfqd)
{
struct io_context *ioc_to_put = bfqd->ioc_to_put;
bfqd->ioc_to_put = NULL;
spin_unlock_irq(&bfqd->lock);
if (ioc_to_put)
put_io_context(ioc_to_put);
}
static void bfq_unlock_put_ioc_restore(struct bfq_data *bfqd,
unsigned long flags)
{
struct io_context *ioc_to_put = bfqd->ioc_to_put;
bfqd->ioc_to_put = NULL;
spin_unlock_irqrestore(&bfqd->lock, flags);
if (ioc_to_put)
put_io_context(ioc_to_put);
}
/**
* bfq_gt - compare two timestamps.
* @a: first ts.
* @b: second ts.
*
* Return @a > @b, dealing with wrapping correctly.
*/
static int bfq_gt(u64 a, u64 b)
{
return (s64)(a - b) > 0;
}
static struct bfq_entity *bfq_root_active_entity(struct rb_root *tree)
{
struct rb_node *node = tree->rb_node;
return rb_entry(node, struct bfq_entity, rb_node);
}
static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd);
static bool bfq_update_parent_budget(struct bfq_entity *next_in_service);
/**
* bfq_update_next_in_service - update sd->next_in_service
* @sd: sched_data for which to perform the update.
* @new_entity: if not NULL, pointer to the entity whose activation,
* requeueing or repositionig triggered the invocation of
* this function.
*
* This function is called to update sd->next_in_service, which, in
* its turn, may change as a consequence of the insertion or
* extraction of an entity into/from one of the active trees of
* sd. These insertions/extractions occur as a consequence of
* activations/deactivations of entities, with some activations being
* 'true' activations, and other activations being requeueings (i.e.,
* implementing the second, requeueing phase of the mechanism used to
* reposition an entity in its active tree; see comments on
* __bfq_activate_entity and __bfq_requeue_entity for details). In
* both the last two activation sub-cases, new_entity points to the
* just activated or requeued entity.
*
* Returns true if sd->next_in_service changes in such a way that
* entity->parent may become the next_in_service for its parent
* entity.
*/
static bool bfq_update_next_in_service(struct bfq_sched_data *sd,
struct bfq_entity *new_entity)
{
struct bfq_entity *next_in_service = sd->next_in_service;
bool parent_sched_may_change = false;
/*
* If this update is triggered by the activation, requeueing
* or repositiong of an entity that does not coincide with
* sd->next_in_service, then a full lookup in the active tree
* can be avoided. In fact, it is enough to check whether the
* just-modified entity has a higher priority than
* sd->next_in_service, or, even if it has the same priority
* as sd->next_in_service, is eligible and has a lower virtual
* finish time than sd->next_in_service. If this compound
* condition holds, then the new entity becomes the new
* next_in_service. Otherwise no change is needed.
*/
if (new_entity && new_entity != sd->next_in_service) {
/*
* Flag used to decide whether to replace
* sd->next_in_service with new_entity. Tentatively
* set to true, and left as true if
* sd->next_in_service is NULL.
*/
bool replace_next = true;
/*
* If there is already a next_in_service candidate
* entity, then compare class priorities or timestamps
* to decide whether to replace sd->service_tree with
* new_entity.
*/
if (next_in_service) {
unsigned int new_entity_class_idx =
bfq_class_idx(new_entity);
struct bfq_service_tree *st =
sd->service_tree + new_entity_class_idx;
/*
* For efficiency, evaluate the most likely
* sub-condition first.
*/
replace_next =
(new_entity_class_idx ==
bfq_class_idx(next_in_service)
&&
!bfq_gt(new_entity->start, st->vtime)
&&
bfq_gt(next_in_service->finish,
new_entity->finish))
||
new_entity_class_idx <
bfq_class_idx(next_in_service);
}
if (replace_next)
next_in_service = new_entity;
} else /* invoked because of a deactivation: lookup needed */
next_in_service = bfq_lookup_next_entity(sd);
if (next_in_service) {
parent_sched_may_change = !sd->next_in_service ||
bfq_update_parent_budget(next_in_service);
}
sd->next_in_service = next_in_service;
if (!next_in_service)
return parent_sched_may_change;
return parent_sched_may_change;
}
#ifdef CONFIG_BFQ_GROUP_IOSCHED
/* both next loops stop at one of the child entities of the root group */
#define for_each_entity(entity) \
for (; entity ; entity = entity->parent)
/*
* For each iteration, compute parent in advance, so as to be safe if
* entity is deallocated during the iteration. Such a deallocation may
* happen as a consequence of a bfq_put_queue that frees the bfq_queue
* containing entity.
*/
#define for_each_entity_safe(entity, parent) \
for (; entity && ({ parent = entity->parent; 1; }); entity = parent)
/*
* Returns true if this budget changes may let next_in_service->parent
* become the next_in_service entity for its parent entity.
*/
static bool bfq_update_parent_budget(struct bfq_entity *next_in_service)
{
struct bfq_entity *bfqg_entity;
struct bfq_group *bfqg;
struct bfq_sched_data *group_sd;
bool ret = false;
group_sd = next_in_service->sched_data;
bfqg = container_of(group_sd, struct bfq_group, sched_data);
/*
* bfq_group's my_entity field is not NULL only if the group
* is not the root group. We must not touch the root entity
* as it must never become an in-service entity.
*/
bfqg_entity = bfqg->my_entity;
if (bfqg_entity) {
if (bfqg_entity->budget > next_in_service->budget)
ret = true;
bfqg_entity->budget = next_in_service->budget;
}
return ret;
}
/*
* This function tells whether entity stops being a candidate for next
* service, according to the following logic.
*
* This function is invoked for an entity that is about to be set in
* service. If such an entity is a queue, then the entity is no longer
* a candidate for next service (i.e, a candidate entity to serve
* after the in-service entity is expired). The function then returns
* true.
*
* In contrast, the entity could stil be a candidate for next service
* if it is not a queue, and has more than one child. In fact, even if
* one of its children is about to be set in service, other children
* may still be the next to serve. As a consequence, a non-queue
* entity is not a candidate for next-service only if it has only one
* child. And only if this condition holds, then the function returns
* true for a non-queue entity.
*/
static bool bfq_no_longer_next_in_service(struct bfq_entity *entity)
{
struct bfq_group *bfqg;
if (bfq_entity_to_bfqq(entity))
return true;
bfqg = container_of(entity, struct bfq_group, entity);
if (bfqg->active_entities == 1)
return true;
return false;
}
#else /* CONFIG_BFQ_GROUP_IOSCHED */
/*
* Next two macros are fake loops when cgroups support is not
* enabled. I fact, in such a case, there is only one level to go up
* (to reach the root group).
*/
#define for_each_entity(entity) \
for (; entity ; entity = NULL)
#define for_each_entity_safe(entity, parent) \
for (parent = NULL; entity ; entity = parent)
static bool bfq_update_parent_budget(struct bfq_entity *next_in_service)
{
return false;
}
static bool bfq_no_longer_next_in_service(struct bfq_entity *entity)
{
return true;
}
#endif /* CONFIG_BFQ_GROUP_IOSCHED */
/*
* Shift for timestamp calculations. This actually limits the maximum
* service allowed in one timestamp delta (small shift values increase it),
* the maximum total weight that can be used for the queues in the system
* (big shift values increase it), and the period of virtual time
* wraparounds.
*/
#define WFQ_SERVICE_SHIFT 22
static struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity)
{
struct bfq_queue *bfqq = NULL;
if (!entity->my_sched_data)
bfqq = container_of(entity, struct bfq_queue, entity);
return bfqq;
}
/**
* bfq_delta - map service into the virtual time domain.
* @service: amount of service.
* @weight: scale factor (weight of an entity or weight sum).
*/
static u64 bfq_delta(unsigned long service, unsigned long weight)
{
u64 d = (u64)service << WFQ_SERVICE_SHIFT;
do_div(d, weight);
return d;
}
/**
* bfq_calc_finish - assign the finish time to an entity.
* @entity: the entity to act upon.
* @service: the service to be charged to the entity.
*/
static void bfq_calc_finish(struct bfq_entity *entity, unsigned long service)
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
entity->finish = entity->start +
bfq_delta(service, entity->weight);
if (bfqq) {
bfq_log_bfqq(bfqq->bfqd, bfqq,
"calc_finish: serv %lu, w %d",
service, entity->weight);
bfq_log_bfqq(bfqq->bfqd, bfqq,
"calc_finish: start %llu, finish %llu, delta %llu",
entity->start, entity->finish,
bfq_delta(service, entity->weight));
}
}
/**
* bfq_entity_of - get an entity from a node.
* @node: the node field of the entity.
*
* Convert a node pointer to the relative entity. This is used only
* to simplify the logic of some functions and not as the generic
* conversion mechanism because, e.g., in the tree walking functions,
* the check for a %NULL value would be redundant.
*/
static struct bfq_entity *bfq_entity_of(struct rb_node *node)
{
struct bfq_entity *entity = NULL;
if (node)
entity = rb_entry(node, struct bfq_entity, rb_node);
return entity;
}
/**
* bfq_extract - remove an entity from a tree.
* @root: the tree root.
* @entity: the entity to remove.
*/
static void bfq_extract(struct rb_root *root, struct bfq_entity *entity)
{
entity->tree = NULL;
rb_erase(&entity->rb_node, root);
}
/**
* bfq_idle_extract - extract an entity from the idle tree.
* @st: the service tree of the owning @entity.
* @entity: the entity being removed.
*/
static void bfq_idle_extract(struct bfq_service_tree *st,
struct bfq_entity *entity)
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
struct rb_node *next;
if (entity == st->first_idle) {
next = rb_next(&entity->rb_node);
st->first_idle = bfq_entity_of(next);
}
if (entity == st->last_idle) {
next = rb_prev(&entity->rb_node);
st->last_idle = bfq_entity_of(next);
}
bfq_extract(&st->idle, entity);
if (bfqq)
list_del(&bfqq->bfqq_list);
}
/**
* bfq_insert - generic tree insertion.
* @root: tree root.
* @entity: entity to insert.
*
* This is used for the idle and the active tree, since they are both
* ordered by finish time.
*/
static void bfq_insert(struct rb_root *root, struct bfq_entity *entity)
{
struct bfq_entity *entry;
struct rb_node **node = &root->rb_node;
struct rb_node *parent = NULL;
while (*node) {
parent = *node;
entry = rb_entry(parent, struct bfq_entity, rb_node);
if (bfq_gt(entry->finish, entity->finish))
node = &parent->rb_left;
else
node = &parent->rb_right;
}
rb_link_node(&entity->rb_node, parent, node);
rb_insert_color(&entity->rb_node, root);
entity->tree = root;
}
/**
* bfq_update_min - update the min_start field of a entity.
* @entity: the entity to update.
* @node: one of its children.
*
* This function is called when @entity may store an invalid value for
* min_start due to updates to the active tree. The function assumes
* that the subtree rooted at @node (which may be its left or its right
* child) has a valid min_start value.
*/
static void bfq_update_min(struct bfq_entity *entity, struct rb_node *node)
{
struct bfq_entity *child;
if (node) {
child = rb_entry(node, struct bfq_entity, rb_node);
if (bfq_gt(entity->min_start, child->min_start))
entity->min_start = child->min_start;
}
}
/**
* bfq_update_active_node - recalculate min_start.
* @node: the node to update.
*
* @node may have changed position or one of its children may have moved,
* this function updates its min_start value. The left and right subtrees
* are assumed to hold a correct min_start value.
*/
static void bfq_update_active_node(struct rb_node *node)
{
struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node);
entity->min_start = entity->start;
bfq_update_min(entity, node->rb_right);
bfq_update_min(entity, node->rb_left);
}
/**
* bfq_update_active_tree - update min_start for the whole active tree.
* @node: the starting node.
*
* @node must be the deepest modified node after an update. This function
* updates its min_start using the values held by its children, assuming
* that they did not change, and then updates all the nodes that may have
* changed in the path to the root. The only nodes that may have changed
* are the ones in the path or their siblings.
*/
static void bfq_update_active_tree(struct rb_node *node)
{
struct rb_node *parent;
up:
bfq_update_active_node(node);
parent = rb_parent(node);
if (!parent)
return;
if (node == parent->rb_left && parent->rb_right)
bfq_update_active_node(parent->rb_right);
else if (parent->rb_left)
bfq_update_active_node(parent->rb_left);
node = parent;
goto up;
}
static void bfq_weights_tree_add(struct bfq_data *bfqd,
struct bfq_entity *entity,
struct rb_root *root);
static void bfq_weights_tree_remove(struct bfq_data *bfqd,
struct bfq_entity *entity,
struct rb_root *root);
/**
* bfq_active_insert - insert an entity in the active tree of its
* group/device.
* @st: the service tree of the entity.
* @entity: the entity being inserted.
*
* The active tree is ordered by finish time, but an extra key is kept
* per each node, containing the minimum value for the start times of
* its children (and the node itself), so it's possible to search for
* the eligible node with the lowest finish time in logarithmic time.
*/
static void bfq_active_insert(struct bfq_service_tree *st,
struct bfq_entity *entity)
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
struct rb_node *node = &entity->rb_node;
#ifdef CONFIG_BFQ_GROUP_IOSCHED
struct bfq_sched_data *sd = NULL;
struct bfq_group *bfqg = NULL;
struct bfq_data *bfqd = NULL;
#endif
bfq_insert(&st->active, entity);
if (node->rb_left)
node = node->rb_left;
else if (node->rb_right)
node = node->rb_right;
bfq_update_active_tree(node);
#ifdef CONFIG_BFQ_GROUP_IOSCHED
sd = entity->sched_data;
bfqg = container_of(sd, struct bfq_group, sched_data);
bfqd = (struct bfq_data *)bfqg->bfqd;
#endif
if (bfqq)
list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list);
#ifdef CONFIG_BFQ_GROUP_IOSCHED
else /* bfq_group */
bfq_weights_tree_add(bfqd, entity, &bfqd->group_weights_tree);
if (bfqg != bfqd->root_group)
bfqg->active_entities++;
#endif
}
/**
* bfq_ioprio_to_weight - calc a weight from an ioprio.
* @ioprio: the ioprio value to convert.
*/
static unsigned short bfq_ioprio_to_weight(int ioprio)
{
return (IOPRIO_BE_NR - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;
}
/**
* bfq_weight_to_ioprio - calc an ioprio from a weight.
* @weight: the weight value to convert.
*
* To preserve as much as possible the old only-ioprio user interface,
* 0 is used as an escape ioprio value for weights (numerically) equal or
* larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF.
*/
static unsigned short bfq_weight_to_ioprio(int weight)
{
return max_t(int, 0,
IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight);
}
static void bfq_get_entity(struct bfq_entity *entity)
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
if (bfqq) {
bfqq->ref++;
bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d",
bfqq, bfqq->ref);
}
}
/**
* bfq_find_deepest - find the deepest node that an extraction can modify.
* @node: the node being removed.
*
* Do the first step of an extraction in an rb tree, looking for the
* node that will replace @node, and returning the deepest node that
* the following modifications to the tree can touch. If @node is the
* last node in the tree return %NULL.
*/
static struct rb_node *bfq_find_deepest(struct rb_node *node)
{
struct rb_node *deepest;
if (!node->rb_right && !node->rb_left)
deepest = rb_parent(node);
else if (!node->rb_right)
deepest = node->rb_left;
else if (!node->rb_left)
deepest = node->rb_right;
else {
deepest = rb_next(node);
if (deepest->rb_right)
deepest = deepest->rb_right;
else if (rb_parent(deepest) != node)
deepest = rb_parent(deepest);
}
return deepest;
}
/**
* bfq_active_extract - remove an entity from the active tree.
* @st: the service_tree containing the tree.
* @entity: the entity being removed.
*/
static void bfq_active_extract(struct bfq_service_tree *st,
struct bfq_entity *entity)
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
struct rb_node *node;
#ifdef CONFIG_BFQ_GROUP_IOSCHED
struct bfq_sched_data *sd = NULL;
struct bfq_group *bfqg = NULL;
struct bfq_data *bfqd = NULL;
#endif
node = bfq_find_deepest(&entity->rb_node);
bfq_extract(&st->active, entity);
if (node)
bfq_update_active_tree(node);
#ifdef CONFIG_BFQ_GROUP_IOSCHED
sd = entity->sched_data;
bfqg = container_of(sd, struct bfq_group, sched_data);
bfqd = (struct bfq_data *)bfqg->bfqd;
#endif
if (bfqq)
list_del(&bfqq->bfqq_list);
#ifdef CONFIG_BFQ_GROUP_IOSCHED
else /* bfq_group */
bfq_weights_tree_remove(bfqd, entity,
&bfqd->group_weights_tree);
if (bfqg != bfqd->root_group)
bfqg->active_entities--;
#endif
}
/**
* bfq_idle_insert - insert an entity into the idle tree.
* @st: the service tree containing the tree.
* @entity: the entity to insert.
*/
static void bfq_idle_insert(struct bfq_service_tree *st,
struct bfq_entity *entity)
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
struct bfq_entity *first_idle = st->first_idle;
struct bfq_entity *last_idle = st->last_idle;
if (!first_idle || bfq_gt(first_idle->finish, entity->finish))
st->first_idle = entity;
if (!last_idle || bfq_gt(entity->finish, last_idle->finish))
st->last_idle = entity;
bfq_insert(&st->idle, entity);
if (bfqq)
list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list);
}
/**
* bfq_forget_entity - do not consider entity any longer for scheduling
* @st: the service tree.
* @entity: the entity being removed.
* @is_in_service: true if entity is currently the in-service entity.
*
* Forget everything about @entity. In addition, if entity represents
* a queue, and the latter is not in service, then release the service
* reference to the queue (the one taken through bfq_get_entity). In
* fact, in this case, there is really no more service reference to
* the queue, as the latter is also outside any service tree. If,
* instead, the queue is in service, then __bfq_bfqd_reset_in_service
* will take care of putting the reference when the queue finally
* stops being served.
*/
static void bfq_forget_entity(struct bfq_service_tree *st,
struct bfq_entity *entity,
bool is_in_service)
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
entity->on_st = false;
st->wsum -= entity->weight;
if (bfqq && !is_in_service)
bfq_put_queue(bfqq);
}
/**
* bfq_put_idle_entity - release the idle tree ref of an entity.
* @st: service tree for the entity.
* @entity: the entity being released.
*/
static void bfq_put_idle_entity(struct bfq_service_tree *st,
struct bfq_entity *entity)
{
bfq_idle_extract(st, entity);
bfq_forget_entity(st, entity,
entity == entity->sched_data->in_service_entity);
}
/**
* bfq_forget_idle - update the idle tree if necessary.
* @st: the service tree to act upon.
*
* To preserve the global O(log N) complexity we only remove one entry here;
* as the idle tree will not grow indefinitely this can be done safely.
*/
static void bfq_forget_idle(struct bfq_service_tree *st)
{
struct bfq_entity *first_idle = st->first_idle;
struct bfq_entity *last_idle = st->last_idle;
if (RB_EMPTY_ROOT(&st->active) && last_idle &&
!bfq_gt(last_idle->finish, st->vtime)) {
/*
* Forget the whole idle tree, increasing the vtime past
* the last finish time of idle entities.
*/
st->vtime = last_idle->finish;
}
if (first_idle && !bfq_gt(first_idle->finish, st->vtime))
bfq_put_idle_entity(st, first_idle);
}
static struct bfq_service_tree *
__bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
struct bfq_entity *entity)
{
struct bfq_service_tree *new_st = old_st;
if (entity->prio_changed) {
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
unsigned int prev_weight, new_weight;
struct bfq_data *bfqd = NULL;
struct rb_root *root;
#ifdef CONFIG_BFQ_GROUP_IOSCHED
struct bfq_sched_data *sd;
struct bfq_group *bfqg;
#endif
if (bfqq)
bfqd = bfqq->bfqd;
#ifdef CONFIG_BFQ_GROUP_IOSCHED
else {
sd = entity->my_sched_data;
bfqg = container_of(sd, struct bfq_group, sched_data);
bfqd = (struct bfq_data *)bfqg->bfqd;
}
#endif
old_st->wsum -= entity->weight;
if (entity->new_weight != entity->orig_weight) {
if (entity->new_weight < BFQ_MIN_WEIGHT ||
entity->new_weight > BFQ_MAX_WEIGHT) {
pr_crit("update_weight_prio: new_weight %d\n",
entity->new_weight);
if (entity->new_weight < BFQ_MIN_WEIGHT)
entity->new_weight = BFQ_MIN_WEIGHT;
else
entity->new_weight = BFQ_MAX_WEIGHT;
}
entity->orig_weight = entity->new_weight;
if (bfqq)
bfqq->ioprio =
bfq_weight_to_ioprio(entity->orig_weight);
}
if (bfqq)
bfqq->ioprio_class = bfqq->new_ioprio_class;
entity->prio_changed = 0;
/*
* NOTE: here we may be changing the weight too early,
* this will cause unfairness. The correct approach
* would have required additional complexity to defer
* weight changes to the proper time instants (i.e.,
* when entity->finish <= old_st->vtime).
*/
new_st = bfq_entity_service_tree(entity);
prev_weight = entity->weight;
new_weight = entity->orig_weight *
(bfqq ? bfqq->wr_coeff : 1);
/*
* If the weight of the entity changes, remove the entity
* from its old weight counter (if there is a counter
* associated with the entity), and add it to the counter
* associated with its new weight.
*/
if (prev_weight != new_weight) {
root = bfqq ? &bfqd->queue_weights_tree :
&bfqd->group_weights_tree;
bfq_weights_tree_remove(bfqd, entity, root);
}
entity->weight = new_weight;
/*
* Add the entity to its weights tree only if it is
* not associated with a weight-raised queue.
*/
if (prev_weight != new_weight &&
(bfqq ? bfqq->wr_coeff == 1 : 1))
/* If we get here, root has been initialized. */
bfq_weights_tree_add(bfqd, entity, root);
new_st->wsum += entity->weight;
if (new_st != old_st)
entity->start = new_st->vtime;
}
return new_st;
}
static void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg);
static struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
/**
* bfq_bfqq_served - update the scheduler status after selection for
* service.
* @bfqq: the queue being served.
* @served: bytes to transfer.
*
* NOTE: this can be optimized, as the timestamps of upper level entities
* are synchronized every time a new bfqq is selected for service. By now,
* we keep it to better check consistency.
*/
static void bfq_bfqq_served(struct bfq_queue *bfqq, int served)
{
struct bfq_entity *entity = &bfqq->entity;
struct bfq_service_tree *st;
for_each_entity(entity) {
st = bfq_entity_service_tree(entity);
entity->service += served;
st->vtime += bfq_delta(served, st->wsum);
bfq_forget_idle(st);
}
bfqg_stats_set_start_empty_time(bfqq_group(bfqq));
bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %d secs", served);
}
/**
* bfq_bfqq_charge_time - charge an amount of service equivalent to the length
* of the time interval during which bfqq has been in
* service.
* @bfqd: the device
* @bfqq: the queue that needs a service update.
* @time_ms: the amount of time during which the queue has received service
*
* If a queue does not consume its budget fast enough, then providing
* the queue with service fairness may impair throughput, more or less
* severely. For this reason, queues that consume their budget slowly
* are provided with time fairness instead of service fairness. This
* goal is achieved through the BFQ scheduling engine, even if such an
* engine works in the service, and not in the time domain. The trick
* is charging these queues with an inflated amount of service, equal
* to the amount of service that they would have received during their
* service slot if they had been fast, i.e., if their requests had
* been dispatched at a rate equal to the estimated peak rate.
*
* It is worth noting that time fairness can cause important
* distortions in terms of bandwidth distribution, on devices with
* internal queueing. The reason is that I/O requests dispatched
* during the service slot of a queue may be served after that service
* slot is finished, and may have a total processing time loosely
* correlated with the duration of the service slot. This is
* especially true for short service slots.
*/
static void bfq_bfqq_charge_time(struct bfq_data *bfqd, struct bfq_queue *bfqq,
unsigned long time_ms)
{
struct bfq_entity *entity = &bfqq->entity;
int tot_serv_to_charge = entity->service;
unsigned int timeout_ms = jiffies_to_msecs(bfq_timeout);
if (time_ms > 0 && time_ms < timeout_ms)
tot_serv_to_charge =
(bfqd->bfq_max_budget * time_ms) / timeout_ms;
if (tot_serv_to_charge < entity->service)
tot_serv_to_charge = entity->service;
/* Increase budget to avoid inconsistencies */
if (tot_serv_to_charge > entity->budget)
entity->budget = tot_serv_to_charge;
bfq_bfqq_served(bfqq,
max_t(int, 0, tot_serv_to_charge - entity->service));
}
static void bfq_update_fin_time_enqueue(struct bfq_entity *entity,
struct bfq_service_tree *st,
bool backshifted)
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
st = __bfq_entity_update_weight_prio(st, entity);
bfq_calc_finish(entity, entity->budget);
/*
* If some queues enjoy backshifting for a while, then their
* (virtual) finish timestamps may happen to become lower and
* lower than the system virtual time. In particular, if
* these queues often happen to be idle for short time
* periods, and during such time periods other queues with
* higher timestamps happen to be busy, then the backshifted
* timestamps of the former queues can become much lower than
* the system virtual time. In fact, to serve the queues with
* higher timestamps while the ones with lower timestamps are
* idle, the system virtual time may be pushed-up to much
* higher values than the finish timestamps of the idle
* queues. As a consequence, the finish timestamps of all new
* or newly activated queues may end up being much larger than
* those of lucky queues with backshifted timestamps. The
* latter queues may then monopolize the device for a lot of
* time. This would simply break service guarantees.
*
* To reduce this problem, push up a little bit the
* backshifted timestamps of the queue associated with this
* entity (only a queue can happen to have the backshifted
* flag set): just enough to let the finish timestamp of the
* queue be equal to the current value of the system virtual
* time. This may introduce a little unfairness among queues
* with backshifted timestamps, but it does not break
* worst-case fairness guarantees.
*
* As a special case, if bfqq is weight-raised, push up
* timestamps much less, to keep very low the probability that
* this push up causes the backshifted finish timestamps of
* weight-raised queues to become higher than the backshifted
* finish timestamps of non weight-raised queues.
*/
if (backshifted && bfq_gt(st->vtime, entity->finish)) {
unsigned long delta = st->vtime - entity->finish;
if (bfqq)
delta /= bfqq->wr_coeff;
entity->start += delta;
entity->finish += delta;
}
bfq_active_insert(st, entity);
}
/**
* __bfq_activate_entity - handle activation of entity.
* @entity: the entity being activated.
* @non_blocking_wait_rq: true if entity was waiting for a request
*
* Called for a 'true' activation, i.e., if entity is not active and
* one of its children receives a new request.
*
* Basically, this function updates the timestamps of entity and
* inserts entity into its active tree, ater possible extracting it
* from its idle tree.
*/
static void __bfq_activate_entity(struct bfq_entity *entity,
bool non_blocking_wait_rq)
{
struct bfq_service_tree *st = bfq_entity_service_tree(entity);
bool backshifted = false;
unsigned long long min_vstart;
/* See comments on bfq_fqq_update_budg_for_activation */
if (non_blocking_wait_rq && bfq_gt(st->vtime, entity->finish)) {
backshifted = true;
min_vstart = entity->finish;
} else
min_vstart = st->vtime;
if (entity->tree == &st->idle) {
/*
* Must be on the idle tree, bfq_idle_extract() will
* check for that.
*/
bfq_idle_extract(st, entity);
entity->start = bfq_gt(min_vstart, entity->finish) ?
min_vstart : entity->finish;
} else {
/*
* The finish time of the entity may be invalid, and
* it is in the past for sure, otherwise the queue
* would have been on the idle tree.
*/
entity->start = min_vstart;
st->wsum += entity->weight;
/*
* entity is about to be inserted into a service tree,
* and then set in service: get a reference to make
* sure entity does not disappear until it is no
* longer in service or scheduled for service.
*/
bfq_get_entity(entity);
entity->on_st = true;
}
bfq_update_fin_time_enqueue(entity, st, backshifted);
}
/**
* __bfq_requeue_entity - handle requeueing or repositioning of an entity.
* @entity: the entity being requeued or repositioned.
*
* Requeueing is needed if this entity stops being served, which
* happens if a leaf descendant entity has expired. On the other hand,
* repositioning is needed if the next_inservice_entity for the child
* entity has changed. See the comments inside the function for
* details.
*
* Basically, this function: 1) removes entity from its active tree if
* present there, 2) updates the timestamps of entity and 3) inserts
* entity back into its active tree (in the new, right position for
* the new values of the timestamps).
*/
static void __bfq_requeue_entity(struct bfq_entity *entity)
{
struct bfq_sched_data *sd = entity->sched_data;
struct bfq_service_tree *st = bfq_entity_service_tree(entity);
if (entity == sd->in_service_entity) {
/*
* We are requeueing the current in-service entity,
* which may have to be done for one of the following
* reasons:
* - entity represents the in-service queue, and the
* in-service queue is being requeued after an
* expiration;
* - entity represents a group, and its budget has
* changed because one of its child entities has
* just been either activated or requeued for some
* reason; the timestamps of the entity need then to
* be updated, and the entity needs to be enqueued
* or repositioned accordingly.
*
* In particular, before requeueing, the start time of
* the entity must be moved forward to account for the
* service that the entity has received while in
* service. This is done by the next instructions. The
* finish time will then be updated according to this
* new value of the start time, and to the budget of
* the entity.
*/
bfq_calc_finish(entity, entity->service);
entity->start = entity->finish;
/*
* In addition, if the entity had more than one child
* when set in service, then was not extracted from
* the active tree. This implies that the position of
* the entity in the active tree may need to be
* changed now, because we have just updated the start
* time of the entity, and we will update its finish
* time in a moment (the requeueing is then, more
* precisely, a repositioning in this case). To
* implement this repositioning, we: 1) dequeue the
* entity here, 2) update the finish time and
* requeue the entity according to the new
* timestamps below.
*/
if (entity->tree)
bfq_active_extract(st, entity);
} else { /* The entity is already active, and not in service */
/*
* In this case, this function gets called only if the
* next_in_service entity below this entity has
* changed, and this change has caused the budget of
* this entity to change, which, finally implies that
* the finish time of this entity must be
* updated. Such an update may cause the scheduling,
* i.e., the position in the active tree, of this
* entity to change. We handle this change by: 1)
* dequeueing the entity here, 2) updating the finish
* time and requeueing the entity according to the new
* timestamps below. This is the same approach as the
* non-extracted-entity sub-case above.
*/
bfq_active_extract(st, entity);
}
bfq_update_fin_time_enqueue(entity, st, false);
}
static void __bfq_activate_requeue_entity(struct bfq_entity *entity,
struct bfq_sched_data *sd,
bool non_blocking_wait_rq)
{
struct bfq_service_tree *st = bfq_entity_service_tree(entity);
if (sd->in_service_entity == entity || entity->tree == &st->active)
/*
* in service or already queued on the active tree,
* requeue or reposition
*/
__bfq_requeue_entity(entity);
else
/*
* Not in service and not queued on its active tree:
* the activity is idle and this is a true activation.
*/
__bfq_activate_entity(entity, non_blocking_wait_rq);
}
/**
* bfq_activate_entity - activate or requeue an entity representing a bfq_queue,
* and activate, requeue or reposition all ancestors
* for which such an update becomes necessary.
* @entity: the entity to activate.
* @non_blocking_wait_rq: true if this entity was waiting for a request
* @requeue: true if this is a requeue, which implies that bfqq is
* being expired; thus ALL its ancestors stop being served and must
* therefore be requeued
*/
static void bfq_activate_requeue_entity(struct bfq_entity *entity,
bool non_blocking_wait_rq,
bool requeue)
{
struct bfq_sched_data *sd;
for_each_entity(entity) {
sd = entity->sched_data;
__bfq_activate_requeue_entity(entity, sd, non_blocking_wait_rq);
if (!bfq_update_next_in_service(sd, entity) && !requeue)
break;
}
}
/**
* __bfq_deactivate_entity - deactivate an entity from its service tree.
* @entity: the entity to deactivate.
* @ins_into_idle_tree: if false, the entity will not be put into the
* idle tree.
*
* Deactivates an entity, independently from its previous state. Must
* be invoked only if entity is on a service tree. Extracts the entity
* from that tree, and if necessary and allowed, puts it on the idle
* tree.
*/
static bool __bfq_deactivate_entity(struct bfq_entity *entity,
bool ins_into_idle_tree)
{
struct bfq_sched_data *sd = entity->sched_data;
struct bfq_service_tree *st = bfq_entity_service_tree(entity);
int is_in_service = entity == sd->in_service_entity;
if (!entity->on_st) /* entity never activated, or already inactive */
return false;
if (is_in_service)
bfq_calc_finish(entity, entity->service);
if (entity->tree == &st->active)
bfq_active_extract(st, entity);
else if (!is_in_service && entity->tree == &st->idle)
bfq_idle_extract(st, entity);
if (!ins_into_idle_tree || !bfq_gt(entity->finish, st->vtime))
bfq_forget_entity(st, entity, is_in_service);
else
bfq_idle_insert(st, entity);
return true;
}
/**
* bfq_deactivate_entity - deactivate an entity representing a bfq_queue.
* @entity: the entity to deactivate.
* @ins_into_idle_tree: true if the entity can be put on the idle tree
*/
static void bfq_deactivate_entity(struct bfq_entity *entity,
bool ins_into_idle_tree,
bool expiration)
{
struct bfq_sched_data *sd;
struct bfq_entity *parent = NULL;
for_each_entity_safe(entity, parent) {
sd = entity->sched_data;
if (!__bfq_deactivate_entity(entity, ins_into_idle_tree)) {
/*
* entity is not in any tree any more, so
* this deactivation is a no-op, and there is
* nothing to change for upper-level entities
* (in case of expiration, this can never
* happen).
*/
return;
}
if (sd->next_in_service == entity)
/*
* entity was the next_in_service entity,
* then, since entity has just been
* deactivated, a new one must be found.
*/
bfq_update_next_in_service(sd, NULL);
if (sd->next_in_service)
/*
* The parent entity is still backlogged,
* because next_in_service is not NULL. So, no
* further upwards deactivation must be
* performed. Yet, next_in_service has
* changed. Then the schedule does need to be
* updated upwards.
*/
break;
/*
* If we get here, then the parent is no more
* backlogged and we need to propagate the
* deactivation upwards. Thus let the loop go on.
*/
/*
* Also let parent be queued into the idle tree on
* deactivation, to preserve service guarantees, and
* assuming that who invoked this function does not
* need parent entities too to be removed completely.
*/
ins_into_idle_tree = true;
}
/*
* If the deactivation loop is fully executed, then there are
* no more entities to touch and next loop is not executed at
* all. Otherwise, requeue remaining entities if they are
* about to stop receiving service, or reposition them if this
* is not the case.
*/
entity = parent;
for_each_entity(entity) {
/*
* Invoke __bfq_requeue_entity on entity, even if
* already active, to requeue/reposition it in the
* active tree (because sd->next_in_service has
* changed)
*/
__bfq_requeue_entity(entity);
sd = entity->sched_data;
if (!bfq_update_next_in_service(sd, entity) &&
!expiration)
/*
* next_in_service unchanged or not causing
* any change in entity->parent->sd, and no
* requeueing needed for expiration: stop
* here.
*/
break;
}
}
/**
* bfq_calc_vtime_jump - compute the value to which the vtime should jump,
* if needed, to have at least one entity eligible.
* @st: the service tree to act upon.
*
* Assumes that st is not empty.
*/
static u64 bfq_calc_vtime_jump(struct bfq_service_tree *st)
{
struct bfq_entity *root_entity = bfq_root_active_entity(&st->active);
if (bfq_gt(root_entity->min_start, st->vtime))
return root_entity->min_start;
return st->vtime;
}
static void bfq_update_vtime(struct bfq_service_tree *st, u64 new_value)
{
if (new_value > st->vtime) {
st->vtime = new_value;
bfq_forget_idle(st);
}
}
/**
* bfq_first_active_entity - find the eligible entity with
* the smallest finish time
* @st: the service tree to select from.
* @vtime: the system virtual to use as a reference for eligibility
*
* This function searches the first schedulable entity, starting from the
* root of the tree and going on the left every time on this side there is
* a subtree with at least one eligible (start >= vtime) entity. The path on
* the right is followed only if a) the left subtree contains no eligible
* entities and b) no eligible entity has been found yet.
*/
static struct bfq_entity *bfq_first_active_entity(struct bfq_service_tree *st,
u64 vtime)
{
struct bfq_entity *entry, *first = NULL;
struct rb_node *node = st->active.rb_node;
while (node) {
entry = rb_entry(node, struct bfq_entity, rb_node);
left:
if (!bfq_gt(entry->start, vtime))
first = entry;
if (node->rb_left) {
entry = rb_entry(node->rb_left,
struct bfq_entity, rb_node);
if (!bfq_gt(entry->min_start, vtime)) {
node = node->rb_left;
goto left;
}
}
if (first)
break;
node = node->rb_right;
}
return first;
}
/**
* __bfq_lookup_next_entity - return the first eligible entity in @st.
* @st: the service tree.
*
* If there is no in-service entity for the sched_data st belongs to,
* then return the entity that will be set in service if:
* 1) the parent entity this st belongs to is set in service;
* 2) no entity belonging to such parent entity undergoes a state change
* that would influence the timestamps of the entity (e.g., becomes idle,
* becomes backlogged, changes its budget, ...).
*
* In this first case, update the virtual time in @st too (see the
* comments on this update inside the function).
*
* In constrast, if there is an in-service entity, then return the
* entity that would be set in service if not only the above
* conditions, but also the next one held true: the currently
* in-service entity, on expiration,
* 1) gets a finish time equal to the current one, or
* 2) is not eligible any more, or
* 3) is idle.
*/
static struct bfq_entity *
__bfq_lookup_next_entity(struct bfq_service_tree *st, bool in_service)
{
struct bfq_entity *entity;
u64 new_vtime;
if (RB_EMPTY_ROOT(&st->active))
return NULL;
/*
* Get the value of the system virtual time for which at
* least one entity is eligible.
*/
new_vtime = bfq_calc_vtime_jump(st);
/*
* If there is no in-service entity for the sched_data this
* active tree belongs to, then push the system virtual time
* up to the value that guarantees that at least one entity is
* eligible. If, instead, there is an in-service entity, then
* do not make any such update, because there is already an
* eligible entity, namely the in-service one (even if the
* entity is not on st, because it was extracted when set in
* service).
*/
if (!in_service)
bfq_update_vtime(st, new_vtime);
entity = bfq_first_active_entity(st, new_vtime);
return entity;
}
/**
* bfq_lookup_next_entity - return the first eligible entity in @sd.
* @sd: the sched_data.
*
* This function is invoked when there has been a change in the trees
* for sd, and we need know what is the new next entity after this
* change.
*/
static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd)
{
struct bfq_service_tree *st = sd->service_tree;
struct bfq_service_tree *idle_class_st = st + (BFQ_IOPRIO_CLASSES - 1);
struct bfq_entity *entity = NULL;
int class_idx = 0;
/*
* Choose from idle class, if needed to guarantee a minimum
* bandwidth to this class (and if there is some active entity
* in idle class). This should also mitigate
* priority-inversion problems in case a low priority task is
* holding file system resources.
*/
if (time_is_before_jiffies(sd->bfq_class_idle_last_service +
BFQ_CL_IDLE_TIMEOUT)) {
if (!RB_EMPTY_ROOT(&idle_class_st->active))
class_idx = BFQ_IOPRIO_CLASSES - 1;
/* About to be served if backlogged, or not yet backlogged */
sd->bfq_class_idle_last_service = jiffies;
}
/*
* Find the next entity to serve for the highest-priority
* class, unless the idle class needs to be served.
*/
for (; class_idx < BFQ_IOPRIO_CLASSES; class_idx++) {
entity = __bfq_lookup_next_entity(st + class_idx,
sd->in_service_entity);
if (entity)
break;
}
if (!entity)
return NULL;
return entity;
}
static bool next_queue_may_preempt(struct bfq_data *bfqd)
{
struct bfq_sched_data *sd = &bfqd->root_group->sched_data;
return sd->next_in_service != sd->in_service_entity;
}
/*
* Get next queue for service.
*/
static struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd)
{
struct bfq_entity *entity = NULL;
struct bfq_sched_data *sd;
struct bfq_queue *bfqq;
if (bfqd->busy_queues == 0)
return NULL;
/*
* Traverse the path from the root to the leaf entity to
* serve. Set in service all the entities visited along the
* way.
*/
sd = &bfqd->root_group->sched_data;
for (; sd ; sd = entity->my_sched_data) {
/*
* WARNING. We are about to set the in-service entity
* to sd->next_in_service, i.e., to the (cached) value
* returned by bfq_lookup_next_entity(sd) the last
* time it was invoked, i.e., the last time when the
* service order in sd changed as a consequence of the
* activation or deactivation of an entity. In this
* respect, if we execute bfq_lookup_next_entity(sd)
* in this very moment, it may, although with low
* probability, yield a different entity than that
* pointed to by sd->next_in_service. This rare event
* happens in case there was no CLASS_IDLE entity to
* serve for sd when bfq_lookup_next_entity(sd) was
* invoked for the last time, while there is now one
* such entity.
*
* If the above event happens, then the scheduling of
* such entity in CLASS_IDLE is postponed until the
* service of the sd->next_in_service entity
* finishes. In fact, when the latter is expired,
* bfq_lookup_next_entity(sd) gets called again,
* exactly to update sd->next_in_service.
*/
/* Make next_in_service entity become in_service_entity */
entity = sd->next_in_service;
sd->in_service_entity = entity;
/*
* Reset the accumulator of the amount of service that
* the entity is about to receive.
*/
entity->service = 0;
/*
* If entity is no longer a candidate for next
* service, then we extract it from its active tree,
* for the following reason. To further boost the
* throughput in some special case, BFQ needs to know
* which is the next candidate entity to serve, while
* there is already an entity in service. In this
* respect, to make it easy to compute/update the next
* candidate entity to serve after the current
* candidate has been set in service, there is a case
* where it is necessary to extract the current
* candidate from its service tree. Such a case is
* when the entity just set in service cannot be also
* a candidate for next service. Details about when
* this conditions holds are reported in the comments
* on the function bfq_no_longer_next_in_service()
* invoked below.
*/
if (bfq_no_longer_next_in_service(entity))
bfq_active_extract(bfq_entity_service_tree(entity),
entity);
/*
* For the same reason why we may have just extracted
* entity from its active tree, we may need to update
* next_in_service for the sched_data of entity too,
* regardless of whether entity has been extracted.
* In fact, even if entity has not been extracted, a
* descendant entity may get extracted. Such an event
* would cause a change in next_in_service for the
* level of the descendant entity, and thus possibly
* back to upper levels.
*
* We cannot perform the resulting needed update
* before the end of this loop, because, to know which
* is the correct next-to-serve candidate entity for
* each level, we need first to find the leaf entity
* to set in service. In fact, only after we know
* which is the next-to-serve leaf entity, we can
* discover whether the parent entity of the leaf
* entity becomes the next-to-serve, and so on.
*/
}
bfqq = bfq_entity_to_bfqq(entity);
/*
* We can finally update all next-to-serve entities along the
* path from the leaf entity just set in service to the root.
*/
for_each_entity(entity) {
struct bfq_sched_data *sd = entity->sched_data;
if (!bfq_update_next_in_service(sd, NULL))
break;
}
return bfqq;
}
static void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd)
{
struct bfq_queue *in_serv_bfqq = bfqd->in_service_queue;
struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity;
struct bfq_entity *entity = in_serv_entity;
if (bfqd->in_service_bic) {
/*
* Schedule the release of a reference to
* bfqd->in_service_bic->icq.ioc to right after the
* scheduler lock is released. This ioc is not
* released immediately, to not risk to possibly take
* an ioc->lock while holding the scheduler lock.
*/
bfqd->ioc_to_put = bfqd->in_service_bic->icq.ioc;
bfqd->in_service_bic = NULL;
}
bfq_clear_bfqq_wait_request(in_serv_bfqq);
hrtimer_try_to_cancel(&bfqd->idle_slice_timer);
bfqd->in_service_queue = NULL;
/*
* When this function is called, all in-service entities have
* been properly deactivated or requeued, so we can safely
* execute the final step: reset in_service_entity along the
* path from entity to the root.
*/
for_each_entity(entity)
entity->sched_data->in_service_entity = NULL;
/*
* in_serv_entity is no longer in service, so, if it is in no
* service tree either, then release the service reference to
* the queue it represents (taken with bfq_get_entity).
*/
if (!in_serv_entity->on_st)
bfq_put_queue(in_serv_bfqq);
}
static void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
bool ins_into_idle_tree, bool expiration)
{
struct bfq_entity *entity = &bfqq->entity;
bfq_deactivate_entity(entity, ins_into_idle_tree, expiration);
}
static void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
struct bfq_entity *entity = &bfqq->entity;
bfq_activate_requeue_entity(entity, bfq_bfqq_non_blocking_wait_rq(bfqq),
false);
bfq_clear_bfqq_non_blocking_wait_rq(bfqq);
}
static void bfq_requeue_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
struct bfq_entity *entity = &bfqq->entity;
bfq_activate_requeue_entity(entity, false,
bfqq == bfqd->in_service_queue);
}
static void bfqg_stats_update_dequeue(struct bfq_group *bfqg);
/*
* Called when the bfqq no longer has requests pending, remove it from
* the service tree. As a special case, it can be invoked during an
* expiration.
*/
static void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq,
bool expiration)
{
bfq_log_bfqq(bfqd, bfqq, "del from busy");
bfq_clear_bfqq_busy(bfqq);
bfqd->busy_queues--;
if (!bfqq->dispatched)
bfq_weights_tree_remove(bfqd, &bfqq->entity,
&bfqd->queue_weights_tree);
if (bfqq->wr_coeff > 1)
bfqd->wr_busy_queues--;
bfqg_stats_update_dequeue(bfqq_group(bfqq));
bfq_deactivate_bfqq(bfqd, bfqq, true, expiration);
}
/*
* Called when an inactive queue receives a new request.
*/
static void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
bfq_log_bfqq(bfqd, bfqq, "add to busy");
bfq_activate_bfqq(bfqd, bfqq);
bfq_mark_bfqq_busy(bfqq);
bfqd->busy_queues++;
if (!bfqq->dispatched)
if (bfqq->wr_coeff == 1)
bfq_weights_tree_add(bfqd, &bfqq->entity,
&bfqd->queue_weights_tree);
if (bfqq->wr_coeff > 1)
bfqd->wr_busy_queues++;
}
#ifdef CONFIG_BFQ_GROUP_IOSCHED
/* bfqg stats flags */
enum bfqg_stats_flags {
BFQG_stats_waiting = 0,
BFQG_stats_idling,
BFQG_stats_empty,
};
#define BFQG_FLAG_FNS(name) \
static void bfqg_stats_mark_##name(struct bfqg_stats *stats) \
{ \
stats->flags |= (1 << BFQG_stats_##name); \
} \
static void bfqg_stats_clear_##name(struct bfqg_stats *stats) \
{ \
stats->flags &= ~(1 << BFQG_stats_##name); \
} \
static int bfqg_stats_##name(struct bfqg_stats *stats) \
{ \
return (stats->flags & (1 << BFQG_stats_##name)) != 0; \
} \
BFQG_FLAG_FNS(waiting)
BFQG_FLAG_FNS(idling)
BFQG_FLAG_FNS(empty)
#undef BFQG_FLAG_FNS
/* This should be called with the queue_lock held. */
static void bfqg_stats_update_group_wait_time(struct bfqg_stats *stats)
{
unsigned long long now;
if (!bfqg_stats_waiting(stats))
return;
now = sched_clock();
if (time_after64(now, stats->start_group_wait_time))
blkg_stat_add(&stats->group_wait_time,
now - stats->start_group_wait_time);
bfqg_stats_clear_waiting(stats);
}
/* This should be called with the queue_lock held. */
static void bfqg_stats_set_start_group_wait_time(struct bfq_group *bfqg,
struct bfq_group *curr_bfqg)
{
struct bfqg_stats *stats = &bfqg->stats;
if (bfqg_stats_waiting(stats))
return;
if (bfqg == curr_bfqg)
return;
stats->start_group_wait_time = sched_clock();
bfqg_stats_mark_waiting(stats);
}
/* This should be called with the queue_lock held. */
static void bfqg_stats_end_empty_time(struct bfqg_stats *stats)
{
unsigned long long now;
if (!bfqg_stats_empty(stats))
return;
now = sched_clock();
if (time_after64(now, stats->start_empty_time))
blkg_stat_add(&stats->empty_time,
now - stats->start_empty_time);
bfqg_stats_clear_empty(stats);
}
static void bfqg_stats_update_dequeue(struct bfq_group *bfqg)
{
blkg_stat_add(&bfqg->stats.dequeue, 1);
}
static void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg)
{
struct bfqg_stats *stats = &bfqg->stats;
if (blkg_rwstat_total(&stats->queued))
return;
/*
* group is already marked empty. This can happen if bfqq got new
* request in parent group and moved to this group while being added
* to service tree. Just ignore the event and move on.
*/
if (bfqg_stats_empty(stats))
return;
stats->start_empty_time = sched_clock();
bfqg_stats_mark_empty(stats);
}
static void bfqg_stats_update_idle_time(struct bfq_group *bfqg)
{
struct bfqg_stats *stats = &bfqg->stats;
if (bfqg_stats_idling(stats)) {
unsigned long long now = sched_clock();
if (time_after64(now, stats->start_idle_time))
blkg_stat_add(&stats->idle_time,
now - stats->start_idle_time);
bfqg_stats_clear_idling(stats);
}
}
static void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg)
{
struct bfqg_stats *stats = &bfqg->stats;
stats->start_idle_time = sched_clock();
bfqg_stats_mark_idling(stats);
}
static void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg)
{
struct bfqg_stats *stats = &bfqg->stats;
blkg_stat_add(&stats->avg_queue_size_sum,
blkg_rwstat_total(&stats->queued));
blkg_stat_add(&stats->avg_queue_size_samples, 1);
bfqg_stats_update_group_wait_time(stats);
}
/*
* blk-cgroup policy-related handlers
* The following functions help in converting between blk-cgroup
* internal structures and BFQ-specific structures.
*/
static struct bfq_group *pd_to_bfqg(struct blkg_policy_data *pd)
{
return pd ? container_of(pd, struct bfq_group, pd) : NULL;
}
static struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg)
{
return pd_to_blkg(&bfqg->pd);
}
static struct blkcg_policy blkcg_policy_bfq;
static struct bfq_group *blkg_to_bfqg(struct blkcg_gq *blkg)
{
return pd_to_bfqg(blkg_to_pd(blkg, &blkcg_policy_bfq));
}
/*
* bfq_group handlers
* The following functions help in navigating the bfq_group hierarchy
* by allowing to find the parent of a bfq_group or the bfq_group
* associated to a bfq_queue.
*/
static struct bfq_group *bfqg_parent(struct bfq_group *bfqg)
{
struct blkcg_gq *pblkg = bfqg_to_blkg(bfqg)->parent;
return pblkg ? blkg_to_bfqg(pblkg) : NULL;
}
static struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
{
struct bfq_entity *group_entity = bfqq->entity.parent;
return group_entity ? container_of(group_entity, struct bfq_group,
entity) :
bfqq->bfqd->root_group;
}
/*
* The following two functions handle get and put of a bfq_group by
* wrapping the related blk-cgroup hooks.
*/
static void bfqg_get(struct bfq_group *bfqg)
{
return blkg_get(bfqg_to_blkg(bfqg));
}
static void bfqg_put(struct bfq_group *bfqg)
{
return blkg_put(bfqg_to_blkg(bfqg));
}
static void bfqg_stats_update_io_add(struct bfq_group *bfqg,
struct bfq_queue *bfqq,
unsigned int op)
{
blkg_rwstat_add(&bfqg->stats.queued, op, 1);
bfqg_stats_end_empty_time(&bfqg->stats);
if (!(bfqq == ((struct bfq_data *)bfqg->bfqd)->in_service_queue))
bfqg_stats_set_start_group_wait_time(bfqg, bfqq_group(bfqq));
}
static void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op)
{
blkg_rwstat_add(&bfqg->stats.queued, op, -1);
}
static void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op)
{
blkg_rwstat_add(&bfqg->stats.merged, op, 1);
}
static void bfqg_stats_update_completion(struct bfq_group *bfqg,
uint64_t start_time, uint64_t io_start_time,
unsigned int op)
{
struct bfqg_stats *stats = &bfqg->stats;
unsigned long long now = sched_clock();
if (time_after64(now, io_start_time))
blkg_rwstat_add(&stats->service_time, op,
now - io_start_time);
if (time_after64(io_start_time, start_time))
blkg_rwstat_add(&stats->wait_time, op,
io_start_time - start_time);
}
/* @stats = 0 */
static void bfqg_stats_reset(struct bfqg_stats *stats)
{
/* queued stats shouldn't be cleared */
blkg_rwstat_reset(&stats->merged);
blkg_rwstat_reset(&stats->service_time);
blkg_rwstat_reset(&stats->wait_time);
blkg_stat_reset(&stats->time);
blkg_stat_reset(&stats->avg_queue_size_sum);
blkg_stat_reset(&stats->avg_queue_size_samples);
blkg_stat_reset(&stats->dequeue);
blkg_stat_reset(&stats->group_wait_time);
blkg_stat_reset(&stats->idle_time);
blkg_stat_reset(&stats->empty_time);
}
/* @to += @from */
static void bfqg_stats_add_aux(struct bfqg_stats *to, struct bfqg_stats *from)
{
if (!to || !from)
return;
/* queued stats shouldn't be cleared */
blkg_rwstat_add_aux(&to->merged, &from->merged);
blkg_rwstat_add_aux(&to->service_time, &from->service_time);
blkg_rwstat_add_aux(&to->wait_time, &from->wait_time);
blkg_stat_add_aux(&from->time, &from->time);
blkg_stat_add_aux(&to->avg_queue_size_sum, &from->avg_queue_size_sum);
blkg_stat_add_aux(&to->avg_queue_size_samples,
&from->avg_queue_size_samples);
blkg_stat_add_aux(&to->dequeue, &from->dequeue);
blkg_stat_add_aux(&to->group_wait_time, &from->group_wait_time);
blkg_stat_add_aux(&to->idle_time, &from->idle_time);
blkg_stat_add_aux(&to->empty_time, &from->empty_time);
}
/*
* Transfer @bfqg's stats to its parent's aux counts so that the ancestors'
* recursive stats can still account for the amount used by this bfqg after
* it's gone.
*/
static void bfqg_stats_xfer_dead(struct bfq_group *bfqg)
{
struct bfq_group *parent;
if (!bfqg) /* root_group */
return;
parent = bfqg_parent(bfqg);
lockdep_assert_held(bfqg_to_blkg(bfqg)->q->queue_lock);
if (unlikely(!parent))
return;
bfqg_stats_add_aux(&parent->stats, &bfqg->stats);
bfqg_stats_reset(&bfqg->stats);
}
static void bfq_init_entity(struct bfq_entity *entity,
struct bfq_group *bfqg)
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
entity->weight = entity->new_weight;
entity->orig_weight = entity->new_weight;
if (bfqq) {
bfqq->ioprio = bfqq->new_ioprio;
bfqq->ioprio_class = bfqq->new_ioprio_class;
bfqg_get(bfqg);
}
entity->parent = bfqg->my_entity; /* NULL for root group */
entity->sched_data = &bfqg->sched_data;
}
static void bfqg_stats_exit(struct bfqg_stats *stats)
{
blkg_rwstat_exit(&stats->merged);
blkg_rwstat_exit(&stats->service_time);
blkg_rwstat_exit(&stats->wait_time);
blkg_rwstat_exit(&stats->queued);
blkg_stat_exit(&stats->time);
blkg_stat_exit(&stats->avg_queue_size_sum);
blkg_stat_exit(&stats->avg_queue_size_samples);
blkg_stat_exit(&stats->dequeue);
blkg_stat_exit(&stats->group_wait_time);
blkg_stat_exit(&stats->idle_time);
blkg_stat_exit(&stats->empty_time);
}
static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp)
{
if (blkg_rwstat_init(&stats->merged, gfp) ||
blkg_rwstat_init(&stats->service_time, gfp) ||
blkg_rwstat_init(&stats->wait_time, gfp) ||
blkg_rwstat_init(&stats->queued, gfp) ||
blkg_stat_init(&stats->time, gfp) ||
blkg_stat_init(&stats->avg_queue_size_sum, gfp) ||
blkg_stat_init(&stats->avg_queue_size_samples, gfp) ||
blkg_stat_init(&stats->dequeue, gfp) ||
blkg_stat_init(&stats->group_wait_time, gfp) ||
blkg_stat_init(&stats->idle_time, gfp) ||
blkg_stat_init(&stats->empty_time, gfp)) {
bfqg_stats_exit(stats);
return -ENOMEM;
}
return 0;
}
static struct bfq_group_data *cpd_to_bfqgd(struct blkcg_policy_data *cpd)
{
return cpd ? container_of(cpd, struct bfq_group_data, pd) : NULL;
}
static struct bfq_group_data *blkcg_to_bfqgd(struct blkcg *blkcg)
{
return cpd_to_bfqgd(blkcg_to_cpd(blkcg, &blkcg_policy_bfq));
}
static struct blkcg_policy_data *bfq_cpd_alloc(gfp_t gfp)
{
struct bfq_group_data *bgd;
bgd = kzalloc(sizeof(*bgd), gfp);
if (!bgd)
return NULL;
return &bgd->pd;
}
static void bfq_cpd_init(struct blkcg_policy_data *cpd)
{
struct bfq_group_data *d = cpd_to_bfqgd(cpd);
d->weight = cgroup_subsys_on_dfl(io_cgrp_subsys) ?
CGROUP_WEIGHT_DFL : BFQ_WEIGHT_LEGACY_DFL;
}
static void bfq_cpd_free(struct blkcg_policy_data *cpd)
{
kfree(cpd_to_bfqgd(cpd));
}
static struct blkg_policy_data *bfq_pd_alloc(gfp_t gfp, int node)
{
struct bfq_group *bfqg;
bfqg = kzalloc_node(sizeof(*bfqg), gfp, node);
if (!bfqg)
return NULL;
if (bfqg_stats_init(&bfqg->stats, gfp)) {
kfree(bfqg);
return NULL;
}
return &bfqg->pd;
}
static void bfq_pd_init(struct blkg_policy_data *pd)
{
struct blkcg_gq *blkg = pd_to_blkg(pd);
struct bfq_group *bfqg = blkg_to_bfqg(blkg);
struct bfq_data *bfqd = blkg->q->elevator->elevator_data;
struct bfq_entity *entity = &bfqg->entity;
struct bfq_group_data *d = blkcg_to_bfqgd(blkg->blkcg);
entity->orig_weight = entity->weight = entity->new_weight = d->weight;
entity->my_sched_data = &bfqg->sched_data;
bfqg->my_entity = entity; /*
* the root_group's will be set to NULL
* in bfq_init_queue()
*/
bfqg->bfqd = bfqd;
bfqg->active_entities = 0;
bfqg->rq_pos_tree = RB_ROOT;
}
static void bfq_pd_free(struct blkg_policy_data *pd)
{
struct bfq_group *bfqg = pd_to_bfqg(pd);
bfqg_stats_exit(&bfqg->stats);
return kfree(bfqg);
}
static void bfq_pd_reset_stats(struct blkg_policy_data *pd)
{
struct bfq_group *bfqg = pd_to_bfqg(pd);
bfqg_stats_reset(&bfqg->stats);
}
static void bfq_group_set_parent(struct bfq_group *bfqg,
struct bfq_group *parent)
{
struct bfq_entity *entity;
entity = &bfqg->entity;
entity->parent = parent->my_entity;
entity->sched_data = &parent->sched_data;
}
static struct bfq_group *bfq_lookup_bfqg(struct bfq_data *bfqd,
struct blkcg *blkcg)
{
struct blkcg_gq *blkg;
blkg = blkg_lookup(blkcg, bfqd->queue);
if (likely(blkg))
return blkg_to_bfqg(blkg);
return NULL;
}
static struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
struct blkcg *blkcg)
{
struct bfq_group *bfqg, *parent;
struct bfq_entity *entity;
bfqg = bfq_lookup_bfqg(bfqd, blkcg);
if (unlikely(!bfqg))
return NULL;
/*
* Update chain of bfq_groups as we might be handling a leaf group
* which, along with some of its relatives, has not been hooked yet
* to the private hierarchy of BFQ.
*/
entity = &bfqg->entity;
for_each_entity(entity) {
bfqg = container_of(entity, struct bfq_group, entity);
if (bfqg != bfqd->root_group) {
parent = bfqg_parent(bfqg);
if (!parent)
parent = bfqd->root_group;
bfq_group_set_parent(bfqg, parent);
}
}
return bfqg;
}
static void bfq_pos_tree_add_move(struct bfq_data *bfqd,
struct bfq_queue *bfqq);
static void bfq_bfqq_expire(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
bool compensate,
enum bfqq_expiration reason);
/**
* bfq_bfqq_move - migrate @bfqq to @bfqg.
* @bfqd: queue descriptor.
* @bfqq: the queue to move.
* @bfqg: the group to move to.
*
* Move @bfqq to @bfqg, deactivating it from its old group and reactivating
* it on the new one. Avoid putting the entity on the old group idle tree.
*
* Must be called under the queue lock; the cgroup owning @bfqg must
* not disappear (by now this just means that we are called under
* rcu_read_lock()).
*/
static void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
struct bfq_group *bfqg)
{
struct bfq_entity *entity = &bfqq->entity;
/* If bfqq is empty, then bfq_bfqq_expire also invokes
* bfq_del_bfqq_busy, thereby removing bfqq and its entity
* from data structures related to current group. Otherwise we
* need to remove bfqq explicitly with bfq_deactivate_bfqq, as
* we do below.
*/
if (bfqq == bfqd->in_service_queue)
bfq_bfqq_expire(bfqd, bfqd->in_service_queue,
false, BFQQE_PREEMPTED);
if (bfq_bfqq_busy(bfqq))
bfq_deactivate_bfqq(bfqd, bfqq, false, false);
else if (entity->on_st)
bfq_put_idle_entity(bfq_entity_service_tree(entity), entity);
bfqg_put(bfqq_group(bfqq));
/*
* Here we use a reference to bfqg. We don't need a refcounter
* as the cgroup reference will not be dropped, so that its
* destroy() callback will not be invoked.
*/
entity->parent = bfqg->my_entity;
entity->sched_data = &bfqg->sched_data;
bfqg_get(bfqg);
if (bfq_bfqq_busy(bfqq)) {
bfq_pos_tree_add_move(bfqd, bfqq);
bfq_activate_bfqq(bfqd, bfqq);
}
if (!bfqd->in_service_queue && !bfqd->rq_in_driver)
bfq_schedule_dispatch(bfqd);
}
/**
* __bfq_bic_change_cgroup - move @bic to @cgroup.
* @bfqd: the queue descriptor.
* @bic: the bic to move.
* @blkcg: the blk-cgroup to move to.
*
* Move bic to blkcg, assuming that bfqd->queue is locked; the caller
* has to make sure that the reference to cgroup is valid across the call.
*
* NOTE: an alternative approach might have been to store the current
* cgroup in bfqq and getting a reference to it, reducing the lookup
* time here, at the price of slightly more complex code.
*/
static struct bfq_group *__bfq_bic_change_cgroup(struct bfq_data *bfqd,
struct bfq_io_cq *bic,
struct blkcg *blkcg)
{
struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0);
struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1);
struct bfq_group *bfqg;
struct bfq_entity *entity;
bfqg = bfq_find_set_group(bfqd, blkcg);
if (unlikely(!bfqg))
bfqg = bfqd->root_group;
if (async_bfqq) {
entity = &async_bfqq->entity;
if (entity->sched_data != &bfqg->sched_data) {
bic_set_bfqq(bic, NULL, 0);
bfq_log_bfqq(bfqd, async_bfqq,
"bic_change_group: %p %d",
async_bfqq, async_bfqq->ref);
bfq_put_queue(async_bfqq);
}
}
if (sync_bfqq) {
entity = &sync_bfqq->entity;
if (entity->sched_data != &bfqg->sched_data)
bfq_bfqq_move(bfqd, sync_bfqq, bfqg);
}
return bfqg;
}
static void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)
{
struct bfq_data *bfqd = bic_to_bfqd(bic);
struct bfq_group *bfqg = NULL;
uint64_t serial_nr;
rcu_read_lock();
serial_nr = bio_blkcg(bio)->css.serial_nr;
/*
* Check whether blkcg has changed. The condition may trigger
* spuriously on a newly created cic but there's no harm.
*/
if (unlikely(!bfqd) || likely(bic->blkcg_serial_nr == serial_nr))
goto out;
bfqg = __bfq_bic_change_cgroup(bfqd, bic, bio_blkcg(bio));
bic->blkcg_serial_nr = serial_nr;
out:
rcu_read_unlock();
}
/**
* bfq_flush_idle_tree - deactivate any entity on the idle tree of @st.
* @st: the service tree being flushed.
*/
static void bfq_flush_idle_tree(struct bfq_service_tree *st)
{
struct bfq_entity *entity = st->first_idle;
for (; entity ; entity = st->first_idle)
__bfq_deactivate_entity(entity, false);
}
/**
* bfq_reparent_leaf_entity - move leaf entity to the root_group.
* @bfqd: the device data structure with the root group.
* @entity: the entity to move.
*/
static void bfq_reparent_leaf_entity(struct bfq_data *bfqd,
struct bfq_entity *entity)
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
bfq_bfqq_move(bfqd, bfqq, bfqd->root_group);
}
/**
* bfq_reparent_active_entities - move to the root group all active
* entities.
* @bfqd: the device data structure with the root group.
* @bfqg: the group to move from.
* @st: the service tree with the entities.
*
* Needs queue_lock to be taken and reference to be valid over the call.
*/
static void bfq_reparent_active_entities(struct bfq_data *bfqd,
struct bfq_group *bfqg,
struct bfq_service_tree *st)
{
struct rb_root *active = &st->active;
struct bfq_entity *entity = NULL;
if (!RB_EMPTY_ROOT(&st->active))
entity = bfq_entity_of(rb_first(active));
for (; entity ; entity = bfq_entity_of(rb_first(active)))
bfq_reparent_leaf_entity(bfqd, entity);
if (bfqg->sched_data.in_service_entity)
bfq_reparent_leaf_entity(bfqd,
bfqg->sched_data.in_service_entity);
}
/**
* bfq_pd_offline - deactivate the entity associated with @pd,
* and reparent its children entities.
* @pd: descriptor of the policy going offline.
*
* blkio already grabs the queue_lock for us, so no need to use
* RCU-based magic
*/
static void bfq_pd_offline(struct blkg_policy_data *pd)
{
struct bfq_service_tree *st;
struct bfq_group *bfqg = pd_to_bfqg(pd);
struct bfq_data *bfqd = bfqg->bfqd;
struct bfq_entity *entity = bfqg->my_entity;
unsigned long flags;
int i;
if (!entity) /* root group */
return;
spin_lock_irqsave(&bfqd->lock, flags);
/*
* Empty all service_trees belonging to this group before
* deactivating the group itself.
*/
for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) {
st = bfqg->sched_data.service_tree + i;
/*
* The idle tree may still contain bfq_queues belonging
* to exited task because they never migrated to a different
* cgroup from the one being destroyed now. No one else
* can access them so it's safe to act without any lock.
*/
bfq_flush_idle_tree(st);
/*
* It may happen that some queues are still active
* (busy) upon group destruction (if the corresponding
* processes have been forced to terminate). We move
* all the leaf entities corresponding to these queues
* to the root_group.
* Also, it may happen that the group has an entity
* in service, which is disconnected from the active
* tree: it must be moved, too.
* There is no need to put the sync queues, as the
* scheduler has taken no reference.
*/
bfq_reparent_active_entities(bfqd, bfqg, st);
}
__bfq_deactivate_entity(entity, false);
bfq_put_async_queues(bfqd, bfqg);
bfq_unlock_put_ioc_restore(bfqd, flags);
/*
* @blkg is going offline and will be ignored by
* blkg_[rw]stat_recursive_sum(). Transfer stats to the parent so
* that they don't get lost. If IOs complete after this point, the
* stats for them will be lost. Oh well...
*/
bfqg_stats_xfer_dead(bfqg);
}
static void bfq_end_wr_async(struct bfq_data *bfqd)
{
struct blkcg_gq *blkg;
list_for_each_entry(blkg, &bfqd->queue->blkg_list, q_node) {
struct bfq_group *bfqg = blkg_to_bfqg(blkg);
bfq_end_wr_async_queues(bfqd, bfqg);
}
bfq_end_wr_async_queues(bfqd, bfqd->root_group);
}
static int bfq_io_show_weight(struct seq_file *sf, void *v)
{
struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
unsigned int val = 0;
if (bfqgd)
val = bfqgd->weight;
seq_printf(sf, "%u\n", val);
return 0;
}
static int bfq_io_set_weight_legacy(struct cgroup_subsys_state *css,
struct cftype *cftype,
u64 val)
{
struct blkcg *blkcg = css_to_blkcg(css);
struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
struct blkcg_gq *blkg;
int ret = -ERANGE;
if (val < BFQ_MIN_WEIGHT || val > BFQ_MAX_WEIGHT)
return ret;
ret = 0;
spin_lock_irq(&blkcg->lock);
bfqgd->weight = (unsigned short)val;
hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
struct bfq_group *bfqg = blkg_to_bfqg(blkg);
if (!bfqg)
continue;
/*
* Setting the prio_changed flag of the entity
* to 1 with new_weight == weight would re-set
* the value of the weight to its ioprio mapping.
* Set the flag only if necessary.
*/
if ((unsigned short)val != bfqg->entity.new_weight) {
bfqg->entity.new_weight = (unsigned short)val;
/*
* Make sure that the above new value has been
* stored in bfqg->entity.new_weight before
* setting the prio_changed flag. In fact,
* this flag may be read asynchronously (in
* critical sections protected by a different
* lock than that held here), and finding this
* flag set may cause the execution of the code
* for updating parameters whose value may
* depend also on bfqg->entity.new_weight (in
* __bfq_entity_update_weight_prio).
* This barrier makes sure that the new value
* of bfqg->entity.new_weight is correctly
* seen in that code.
*/
smp_wmb();
bfqg->entity.prio_changed = 1;
}
}
spin_unlock_irq(&blkcg->lock);
return ret;
}
static ssize_t bfq_io_set_weight(struct kernfs_open_file *of,
char *buf, size_t nbytes,
loff_t off)
{
u64 weight;
/* First unsigned long found in the file is used */
int ret = kstrtoull(strim(buf), 0, &weight);
if (ret)
return ret;
return bfq_io_set_weight_legacy(of_css(of), NULL, weight);
}
static int bfqg_print_stat(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_stat,
&blkcg_policy_bfq, seq_cft(sf)->private, false);
return 0;
}
static int bfqg_print_rwstat(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_rwstat,
&blkcg_policy_bfq, seq_cft(sf)->private, true);
return 0;
}
static u64 bfqg_prfill_stat_recursive(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
u64 sum = blkg_stat_recursive_sum(pd_to_blkg(pd),
&blkcg_policy_bfq, off);
return __blkg_prfill_u64(sf, pd, sum);
}
static u64 bfqg_prfill_rwstat_recursive(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
struct blkg_rwstat sum = blkg_rwstat_recursive_sum(pd_to_blkg(pd),
&blkcg_policy_bfq,
off);
return __blkg_prfill_rwstat(sf, pd, &sum);
}
static int bfqg_print_stat_recursive(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
bfqg_prfill_stat_recursive, &blkcg_policy_bfq,
seq_cft(sf)->private, false);
return 0;
}
static int bfqg_print_rwstat_recursive(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
bfqg_prfill_rwstat_recursive, &blkcg_policy_bfq,
seq_cft(sf)->private, true);
return 0;
}
static u64 bfqg_prfill_sectors(struct seq_file *sf, struct blkg_policy_data *pd,
int off)
{
u64 sum = blkg_rwstat_total(&pd->blkg->stat_bytes);
return __blkg_prfill_u64(sf, pd, sum >> 9);
}
static int bfqg_print_stat_sectors(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
bfqg_prfill_sectors, &blkcg_policy_bfq, 0, false);
return 0;
}
static u64 bfqg_prfill_sectors_recursive(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
struct blkg_rwstat tmp = blkg_rwstat_recursive_sum(pd->blkg, NULL,
offsetof(struct blkcg_gq, stat_bytes));
u64 sum = atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) +
atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_WRITE]);
return __blkg_prfill_u64(sf, pd, sum >> 9);
}
static int bfqg_print_stat_sectors_recursive(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
bfqg_prfill_sectors_recursive, &blkcg_policy_bfq, 0,
false);
return 0;
}
static u64 bfqg_prfill_avg_queue_size(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
struct bfq_group *bfqg = pd_to_bfqg(pd);
u64 samples = blkg_stat_read(&bfqg->stats.avg_queue_size_samples);
u64 v = 0;
if (samples) {
v = blkg_stat_read(&bfqg->stats.avg_queue_size_sum);
v = div64_u64(v, samples);
}
__blkg_prfill_u64(sf, pd, v);
return 0;
}
/* print avg_queue_size */
static int bfqg_print_avg_queue_size(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
bfqg_prfill_avg_queue_size, &blkcg_policy_bfq,
0, false);
return 0;
}
static struct bfq_group *
bfq_create_group_hierarchy(struct bfq_data *bfqd, int node)
{
int ret;
ret = blkcg_activate_policy(bfqd->queue, &blkcg_policy_bfq);
if (ret)
return NULL;
return blkg_to_bfqg(bfqd->queue->root_blkg);
}
static struct cftype bfq_blkcg_legacy_files[] = {
{
.name = "bfq.weight",
.flags = CFTYPE_NOT_ON_ROOT,
.seq_show = bfq_io_show_weight,
.write_u64 = bfq_io_set_weight_legacy,
},
/* statistics, covers only the tasks in the bfqg */
{
.name = "bfq.time",
.private = offsetof(struct bfq_group, stats.time),
.seq_show = bfqg_print_stat,
},
{
.name = "bfq.sectors",
.seq_show = bfqg_print_stat_sectors,
},
{
.name = "bfq.io_service_bytes",
.private = (unsigned long)&blkcg_policy_bfq,
.seq_show = blkg_print_stat_bytes,
},
{
.name = "bfq.io_serviced",
.private = (unsigned long)&blkcg_policy_bfq,
.seq_show = blkg_print_stat_ios,
},
{
.name = "bfq.io_service_time",
.private = offsetof(struct bfq_group, stats.service_time),
.seq_show = bfqg_print_rwstat,
},
{
.name = "bfq.io_wait_time",
.private = offsetof(struct bfq_group, stats.wait_time),
.seq_show = bfqg_print_rwstat,
},
{
.name = "bfq.io_merged",
.private = offsetof(struct bfq_group, stats.merged),
.seq_show = bfqg_print_rwstat,
},
{
.name = "bfq.io_queued",
.private = offsetof(struct bfq_group, stats.queued),
.seq_show = bfqg_print_rwstat,
},
/* the same statictics which cover the bfqg and its descendants */
{
.name = "bfq.time_recursive",
.private = offsetof(struct bfq_group, stats.time),
.seq_show = bfqg_print_stat_recursive,
},
{
.name = "bfq.sectors_recursive",
.seq_show = bfqg_print_stat_sectors_recursive,
},
{
.name = "bfq.io_service_bytes_recursive",
.private = (unsigned long)&blkcg_policy_bfq,
.seq_show = blkg_print_stat_bytes_recursive,
},
{
.name = "bfq.io_serviced_recursive",
.private = (unsigned long)&blkcg_policy_bfq,
.seq_show = blkg_print_stat_ios_recursive,
},
{
.name = "bfq.io_service_time_recursive",
.private = offsetof(struct bfq_group, stats.service_time),
.seq_show = bfqg_print_rwstat_recursive,
},
{
.name = "bfq.io_wait_time_recursive",
.private = offsetof(struct bfq_group, stats.wait_time),
.seq_show = bfqg_print_rwstat_recursive,
},
{
.name = "bfq.io_merged_recursive",
.private = offsetof(struct bfq_group, stats.merged),
.seq_show = bfqg_print_rwstat_recursive,
},
{
.name = "bfq.io_queued_recursive",
.private = offsetof(struct bfq_group, stats.queued),
.seq_show = bfqg_print_rwstat_recursive,
},
{
.name = "bfq.avg_queue_size",
.seq_show = bfqg_print_avg_queue_size,
},
{
.name = "bfq.group_wait_time",
.private = offsetof(struct bfq_group, stats.group_wait_time),
.seq_show = bfqg_print_stat,
},
{
.name = "bfq.idle_time",
.private = offsetof(struct bfq_group, stats.idle_time),
.seq_show = bfqg_print_stat,
},
{
.name = "bfq.empty_time",
.private = offsetof(struct bfq_group, stats.empty_time),
.seq_show = bfqg_print_stat,
},
{
.name = "bfq.dequeue",
.private = offsetof(struct bfq_group, stats.dequeue),
.seq_show = bfqg_print_stat,
},
{ } /* terminate */
};
static struct cftype bfq_blkg_files[] = {
{
.name = "bfq.weight",
.flags = CFTYPE_NOT_ON_ROOT,
.seq_show = bfq_io_show_weight,
.write = bfq_io_set_weight,
},
{} /* terminate */
};
#else /* CONFIG_BFQ_GROUP_IOSCHED */
static inline void bfqg_stats_update_io_add(struct bfq_group *bfqg,
struct bfq_queue *bfqq, unsigned int op) { }
static inline void
bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op) { }
static inline void
bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op) { }
static inline void bfqg_stats_update_completion(struct bfq_group *bfqg,
uint64_t start_time, uint64_t io_start_time,
unsigned int op) { }
static inline void
bfqg_stats_set_start_group_wait_time(struct bfq_group *bfqg,
struct bfq_group *curr_bfqg) { }
static inline void bfqg_stats_end_empty_time(struct bfqg_stats *stats) { }
static inline void bfqg_stats_update_dequeue(struct bfq_group *bfqg) { }
static inline void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg) { }
static inline void bfqg_stats_update_idle_time(struct bfq_group *bfqg) { }
static inline void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg) { }
static inline void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg) { }
static void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
struct bfq_group *bfqg) {}
static void bfq_init_entity(struct bfq_entity *entity,
struct bfq_group *bfqg)
{
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
entity->weight = entity->new_weight;
entity->orig_weight = entity->new_weight;
if (bfqq) {
bfqq->ioprio = bfqq->new_ioprio;
bfqq->ioprio_class = bfqq->new_ioprio_class;
}
entity->sched_data = &bfqg->sched_data;
}
static void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio) {}
static void bfq_end_wr_async(struct bfq_data *bfqd)
{
bfq_end_wr_async_queues(bfqd, bfqd->root_group);
}
static struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
struct blkcg *blkcg)
{
return bfqd->root_group;
}
static struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
{
return bfqq->bfqd->root_group;
}
static struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd,
int node)
{
struct bfq_group *bfqg;
int i;
bfqg = kmalloc_node(sizeof(*bfqg), GFP_KERNEL | __GFP_ZERO, node);
if (!bfqg)
return NULL;
for (i = 0; i < BFQ_IOPRIO_CLASSES; i++)
bfqg->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT;
return bfqg;
}
#endif /* CONFIG_BFQ_GROUP_IOSCHED */
#define bfq_class_idle(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
#define bfq_class_rt(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_RT)
#define bfq_sample_valid(samples) ((samples) > 80)
/*
* Lifted from AS - choose which of rq1 and rq2 that is best served now.
* We choose the request that is closesr to the head right now. Distance
* behind the head is penalized and only allowed to a certain extent.
*/
static struct request *bfq_choose_req(struct bfq_data *bfqd,
struct request *rq1,
struct request *rq2,
sector_t last)
{
sector_t s1, s2, d1 = 0, d2 = 0;
unsigned long back_max;
#define BFQ_RQ1_WRAP 0x01 /* request 1 wraps */
#define BFQ_RQ2_WRAP 0x02 /* request 2 wraps */
unsigned int wrap = 0; /* bit mask: requests behind the disk head? */
if (!rq1 || rq1 == rq2)
return rq2;
if (!rq2)
return rq1;
if (rq_is_sync(rq1) && !rq_is_sync(rq2))
return rq1;
else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
return rq2;
if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META))
return rq1;
else if ((rq2->cmd_flags & REQ_META) && !(rq1->cmd_flags & REQ_META))
return rq2;
s1 = blk_rq_pos(rq1);
s2 = blk_rq_pos(rq2);
/*
* By definition, 1KiB is 2 sectors.
*/
back_max = bfqd->bfq_back_max * 2;
/*
* Strict one way elevator _except_ in the case where we allow
* short backward seeks which are biased as twice the cost of a
* similar forward seek.
*/
if (s1 >= last)
d1 = s1 - last;
else if (s1 + back_max >= last)
d1 = (last - s1) * bfqd->bfq_back_penalty;
else
wrap |= BFQ_RQ1_WRAP;
if (s2 >= last)
d2 = s2 - last;
else if (s2 + back_max >= last)
d2 = (last - s2) * bfqd->bfq_back_penalty;
else
wrap |= BFQ_RQ2_WRAP;
/* Found required data */
/*
* By doing switch() on the bit mask "wrap" we avoid having to
* check two variables for all permutations: --> faster!
*/
switch (wrap) {
case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
if (d1 < d2)
return rq1;
else if (d2 < d1)
return rq2;
if (s1 >= s2)
return rq1;
else
return rq2;
case BFQ_RQ2_WRAP:
return rq1;
case BFQ_RQ1_WRAP:
return rq2;
case BFQ_RQ1_WRAP|BFQ_RQ2_WRAP: /* both rqs wrapped */
default:
/*
* Since both rqs are wrapped,
* start with the one that's further behind head
* (--> only *one* back seek required),
* since back seek takes more time than forward.
*/
if (s1 <= s2)
return rq1;
else
return rq2;
}
}
static struct bfq_queue *
bfq_rq_pos_tree_lookup(struct bfq_data *bfqd, struct rb_root *root,
sector_t sector, struct rb_node **ret_parent,
struct rb_node ***rb_link)
{
struct rb_node **p, *parent;
struct bfq_queue *bfqq = NULL;
parent = NULL;
p = &root->rb_node;
while (*p) {
struct rb_node **n;
parent = *p;
bfqq = rb_entry(parent, struct bfq_queue, pos_node);
/*
* Sort strictly based on sector. Smallest to the left,
* largest to the right.
*/
if (sector > blk_rq_pos(bfqq->next_rq))
n = &(*p)->rb_right;
else if (sector < blk_rq_pos(bfqq->next_rq))
n = &(*p)->rb_left;
else
break;
p = n;
bfqq = NULL;
}
*ret_parent = parent;
if (rb_link)
*rb_link = p;
bfq_log(bfqd, "rq_pos_tree_lookup %llu: returning %d",
(unsigned long long)sector,
bfqq ? bfqq->pid : 0);
return bfqq;
}
static void bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
struct rb_node **p, *parent;
struct bfq_queue *__bfqq;
if (bfqq->pos_root) {
rb_erase(&bfqq->pos_node, bfqq->pos_root);
bfqq->pos_root = NULL;
}
if (bfq_class_idle(bfqq))
return;
if (!bfqq->next_rq)
return;
bfqq->pos_root = &bfq_bfqq_to_bfqg(bfqq)->rq_pos_tree;
__bfqq = bfq_rq_pos_tree_lookup(bfqd, bfqq->pos_root,
blk_rq_pos(bfqq->next_rq), &parent, &p);
if (!__bfqq) {
rb_link_node(&bfqq->pos_node, parent, p);
rb_insert_color(&bfqq->pos_node, bfqq->pos_root);
} else
bfqq->pos_root = NULL;
}
/*
* Tell whether there are active queues or groups with differentiated weights.
*/
static bool bfq_differentiated_weights(struct bfq_data *bfqd)
{
/*
* For weights to differ, at least one of the trees must contain
* at least two nodes.
*/
return (!RB_EMPTY_ROOT(&bfqd->queue_weights_tree) &&
(bfqd->queue_weights_tree.rb_node->rb_left ||
bfqd->queue_weights_tree.rb_node->rb_right)
#ifdef CONFIG_BFQ_GROUP_IOSCHED
) ||
(!RB_EMPTY_ROOT(&bfqd->group_weights_tree) &&
(bfqd->group_weights_tree.rb_node->rb_left ||
bfqd->group_weights_tree.rb_node->rb_right)
#endif
);
}
/*
* The following function returns true if every queue must receive the
* same share of the throughput (this condition is used when deciding
* whether idling may be disabled, see the comments in the function
* bfq_bfqq_may_idle()).
*
* Such a scenario occurs when:
* 1) all active queues have the same weight,
* 2) all active groups at the same level in the groups tree have the same
* weight,
* 3) all active groups at the same level in the groups tree have the same
* number of children.
*
* Unfortunately, keeping the necessary state for evaluating exactly the
* above symmetry conditions would be quite complex and time-consuming.
* Therefore this function evaluates, instead, the following stronger
* sub-conditions, for which it is much easier to maintain the needed
* state:
* 1) all active queues have the same weight,
* 2) all active groups have the same weight,
* 3) all active groups have at most one active child each.
* In particular, the last two conditions are always true if hierarchical
* support and the cgroups interface are not enabled, thus no state needs
* to be maintained in this case.
*/
static bool bfq_symmetric_scenario(struct bfq_data *bfqd)
{
return !bfq_differentiated_weights(bfqd);
}
/*
* If the weight-counter tree passed as input contains no counter for
* the weight of the input entity, then add that counter; otherwise just
* increment the existing counter.
*
* Note that weight-counter trees contain few nodes in mostly symmetric
* scenarios. For example, if all queues have the same weight, then the
* weight-counter tree for the queues may contain at most one node.
* This holds even if low_latency is on, because weight-raised queues
* are not inserted in the tree.
* In most scenarios, the rate at which nodes are created/destroyed
* should be low too.
*/
static void bfq_weights_tree_add(struct bfq_data *bfqd,
struct bfq_entity *entity,
struct rb_root *root)
{
struct rb_node **new = &(root->rb_node), *parent = NULL;
/*
* Do not insert if the entity is already associated with a
* counter, which happens if:
* 1) the entity is associated with a queue,
* 2) a request arrival has caused the queue to become both
* non-weight-raised, and hence change its weight, and
* backlogged; in this respect, each of the two events
* causes an invocation of this function,
* 3) this is the invocation of this function caused by the
* second event. This second invocation is actually useless,
* and we handle this fact by exiting immediately. More
* efficient or clearer solutions might possibly be adopted.
*/
if (entity->weight_counter)
return;
while (*new) {
struct bfq_weight_counter *__counter = container_of(*new,
struct bfq_weight_counter,
weights_node);
parent = *new;
if (entity->weight == __counter->weight) {
entity->weight_counter = __counter;
goto inc_counter;
}
if (entity->weight < __counter->weight)
new = &((*new)->rb_left);
else
new = &((*new)->rb_right);
}
entity->weight_counter = kzalloc(sizeof(struct bfq_weight_counter),
GFP_ATOMIC);
/*
* In the unlucky event of an allocation failure, we just
* exit. This will cause the weight of entity to not be
* considered in bfq_differentiated_weights, which, in its
* turn, causes the scenario to be deemed wrongly symmetric in
* case entity's weight would have been the only weight making
* the scenario asymmetric. On the bright side, no unbalance
* will however occur when entity becomes inactive again (the
* invocation of this function is triggered by an activation
* of entity). In fact, bfq_weights_tree_remove does nothing
* if !entity->weight_counter.
*/
if (unlikely(!entity->weight_counter))
return;
entity->weight_counter->weight = entity->weight;
rb_link_node(&entity->weight_counter->weights_node, parent, new);
rb_insert_color(&entity->weight_counter->weights_node, root);
inc_counter:
entity->weight_counter->num_active++;
}
/*
* Decrement the weight counter associated with the entity, and, if the
* counter reaches 0, remove the counter from the tree.
* See the comments to the function bfq_weights_tree_add() for considerations
* about overhead.
*/
static void bfq_weights_tree_remove(struct bfq_data *bfqd,
struct bfq_entity *entity,
struct rb_root *root)
{
if (!entity->weight_counter)
return;
entity->weight_counter->num_active--;
if (entity->weight_counter->num_active > 0)
goto reset_entity_pointer;
rb_erase(&entity->weight_counter->weights_node, root);
kfree(entity->weight_counter);
reset_entity_pointer:
entity->weight_counter = NULL;
}
/*
* Return expired entry, or NULL to just start from scratch in rbtree.
*/
static struct request *bfq_check_fifo(struct bfq_queue *bfqq,
struct request *last)
{
struct request *rq;
if (bfq_bfqq_fifo_expire(bfqq))
return NULL;
bfq_mark_bfqq_fifo_expire(bfqq);
rq = rq_entry_fifo(bfqq->fifo.next);
if (rq == last || ktime_get_ns() < rq->fifo_time)
return NULL;
bfq_log_bfqq(bfqq->bfqd, bfqq, "check_fifo: returned %p", rq);
return rq;
}
static struct request *bfq_find_next_rq(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
struct request *last)
{
struct rb_node *rbnext = rb_next(&last->rb_node);
struct rb_node *rbprev = rb_prev(&last->rb_node);
struct request *next, *prev = NULL;
/* Follow expired path, else get first next available. */
next = bfq_check_fifo(bfqq, last);
if (next)
return next;
if (rbprev)
prev = rb_entry_rq(rbprev);
if (rbnext)
next = rb_entry_rq(rbnext);
else {
rbnext = rb_first(&bfqq->sort_list);
if (rbnext && rbnext != &last->rb_node)
next = rb_entry_rq(rbnext);
}
return bfq_choose_req(bfqd, next, prev, blk_rq_pos(last));
}
/* see the definition of bfq_async_charge_factor for details */
static unsigned long bfq_serv_to_charge(struct request *rq,
struct bfq_queue *bfqq)
{
if (bfq_bfqq_sync(bfqq) || bfqq->wr_coeff > 1)
return blk_rq_sectors(rq);
/*
* If there are no weight-raised queues, then amplify service
* by just the async charge factor; otherwise amplify service
* by twice the async charge factor, to further reduce latency
* for weight-raised queues.
*/
if (bfqq->bfqd->wr_busy_queues == 0)
return blk_rq_sectors(rq) * bfq_async_charge_factor;
return blk_rq_sectors(rq) * 2 * bfq_async_charge_factor;
}
/**
* bfq_updated_next_req - update the queue after a new next_rq selection.
* @bfqd: the device data the queue belongs to.
* @bfqq: the queue to update.
*
* If the first request of a queue changes we make sure that the queue
* has enough budget to serve at least its first request (if the
* request has grown). We do this because if the queue has not enough
* budget for its first request, it has to go through two dispatch
* rounds to actually get it dispatched.
*/
static void bfq_updated_next_req(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
struct bfq_entity *entity = &bfqq->entity;
struct request *next_rq = bfqq->next_rq;
unsigned long new_budget;
if (!next_rq)
return;
if (bfqq == bfqd->in_service_queue)
/*
* In order not to break guarantees, budgets cannot be
* changed after an entity has been selected.
*/
return;
new_budget = max_t(unsigned long, bfqq->max_budget,
bfq_serv_to_charge(next_rq, bfqq));
if (entity->budget != new_budget) {
entity->budget = new_budget;
bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu",
new_budget);
bfq_requeue_bfqq(bfqd, bfqq);
}
}
static void
bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
{
if (bic->saved_idle_window)
bfq_mark_bfqq_idle_window(bfqq);
else
bfq_clear_bfqq_idle_window(bfqq);
if (bic->saved_IO_bound)
bfq_mark_bfqq_IO_bound(bfqq);
else
bfq_clear_bfqq_IO_bound(bfqq);
bfqq->ttime = bic->saved_ttime;
bfqq->wr_coeff = bic->saved_wr_coeff;
bfqq->wr_start_at_switch_to_srt = bic->saved_wr_start_at_switch_to_srt;
bfqq->last_wr_start_finish = bic->saved_last_wr_start_finish;
bfqq->wr_cur_max_time = bic->saved_wr_cur_max_time;
if (bfqq->wr_coeff > 1 && (bfq_bfqq_in_large_burst(bfqq) ||
time_is_before_jiffies(bfqq->last_wr_start_finish +
bfqq->wr_cur_max_time))) {
bfq_log_bfqq(bfqq->bfqd, bfqq,
"resume state: switching off wr");
bfqq->wr_coeff = 1;
}
/* make sure weight will be updated, however we got here */
bfqq->entity.prio_changed = 1;
}
static int bfqq_process_refs(struct bfq_queue *bfqq)
{
return bfqq->ref - bfqq->allocated - bfqq->entity.on_st;
}
/* Empty burst list and add just bfqq (see comments on bfq_handle_burst) */
static void bfq_reset_burst_list(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
struct bfq_queue *item;
struct hlist_node *n;
hlist_for_each_entry_safe(item, n, &bfqd->burst_list, burst_list_node)
hlist_del_init(&item->burst_list_node);
hlist_add_head(&bfqq->burst_list_node, &bfqd->burst_list);
bfqd->burst_size = 1;
bfqd->burst_parent_entity = bfqq->entity.parent;
}
/* Add bfqq to the list of queues in current burst (see bfq_handle_burst) */
static void bfq_add_to_burst(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
/* Increment burst size to take into account also bfqq */
bfqd->burst_size++;
if (bfqd->burst_size == bfqd->bfq_large_burst_thresh) {
struct bfq_queue *pos, *bfqq_item;
struct hlist_node *n;
/*
* Enough queues have been activated shortly after each
* other to consider this burst as large.
*/
bfqd->large_burst = true;
/*
* We can now mark all queues in the burst list as
* belonging to a large burst.
*/
hlist_for_each_entry(bfqq_item, &bfqd->burst_list,
burst_list_node)
bfq_mark_bfqq_in_large_burst(bfqq_item);
bfq_mark_bfqq_in_large_burst(bfqq);
/*
* From now on, and until the current burst finishes, any
* new queue being activated shortly after the last queue
* was inserted in the burst can be immediately marked as
* belonging to a large burst. So the burst list is not
* needed any more. Remove it.
*/
hlist_for_each_entry_safe(pos, n, &bfqd->burst_list,
burst_list_node)
hlist_del_init(&pos->burst_list_node);
} else /*
* Burst not yet large: add bfqq to the burst list. Do
* not increment the ref counter for bfqq, because bfqq
* is removed from the burst list before freeing bfqq
* in put_queue.
*/
hlist_add_head(&bfqq->burst_list_node, &bfqd->burst_list);
}
/*
* If many queues belonging to the same group happen to be created
* shortly after each other, then the processes associated with these
* queues have typically a common goal. In particular, bursts of queue
* creations are usually caused by services or applications that spawn
* many parallel threads/processes. Examples are systemd during boot,
* or git grep. To help these processes get their job done as soon as
* possible, it is usually better to not grant either weight-raising
* or device idling to their queues.
*
* In this comment we describe, firstly, the reasons why this fact
* holds, and, secondly, the next function, which implements the main
* steps needed to properly mark these queues so that they can then be
* treated in a different way.
*
* The above services or applications benefit mostly from a high
* throughput: the quicker the requests of the activated queues are
* cumulatively served, the sooner the target job of these queues gets
* completed. As a consequence, weight-raising any of these queues,
* which also implies idling the device for it, is almost always
* counterproductive. In most cases it just lowers throughput.
*
* On the other hand, a burst of queue creations may be caused also by
* the start of an application that does not consist of a lot of
* parallel I/O-bound threads. In fact, with a complex application,
* several short processes may need to be executed to start-up the
* application. In this respect, to start an application as quickly as
* possible, the best thing to do is in any case to privilege the I/O
* related to the application with respect to all other
* I/O. Therefore, the best strategy to start as quickly as possible
* an application that causes a burst of queue creations is to
* weight-raise all the queues created during the burst. This is the
* exact opposite of the best strategy for the other type of bursts.
*
* In the end, to take the best action for each of the two cases, the
* two types of bursts need to be distinguished. Fortunately, this
* seems relatively easy, by looking at the sizes of the bursts. In
* particular, we found a threshold such that only bursts with a
* larger size than that threshold are apparently caused by
* services or commands such as systemd or git grep. For brevity,
* hereafter we call just 'large' these bursts. BFQ *does not*
* weight-raise queues whose creation occurs in a large burst. In
* addition, for each of these queues BFQ performs or does not perform
* idling depending on which choice boosts the throughput more. The
* exact choice depends on the device and request pattern at
* hand.
*
* Unfortunately, false positives may occur while an interactive task
* is starting (e.g., an application is being started). The
* consequence is that the queues associated with the task do not
* enjoy weight raising as expected. Fortunately these false positives
* are very rare. They typically occur if some service happens to
* start doing I/O exactly when the interactive task starts.
*
* Turning back to the next function, it implements all the steps
* needed to detect the occurrence of a large burst and to properly
* mark all the queues belonging to it (so that they can then be
* treated in a different way). This goal is achieved by maintaining a
* "burst list" that holds, temporarily, the queues that belong to the
* burst in progress. The list is then used to mark these queues as
* belonging to a large burst if the burst does become large. The main
* steps are the following.
*
* . when the very first queue is created, the queue is inserted into the
* list (as it could be the first queue in a possible burst)
*
* . if the current burst has not yet become large, and a queue Q that does
* not yet belong to the burst is activated shortly after the last time
* at which a new queue entered the burst list, then the function appends
* Q to the burst list
*
* . if, as a consequence of the previous step, the burst size reaches
* the large-burst threshold, then
*
* . all the queues in the burst list are marked as belonging to a
* large burst
*
* . the burst list is deleted; in fact, the burst list already served
* its purpose (keeping temporarily track of the queues in a burst,
* so as to be able to mark them as belonging to a large burst in the
* previous sub-step), and now is not needed any more
*
* . the device enters a large-burst mode
*
* . if a queue Q that does not belong to the burst is created while
* the device is in large-burst mode and shortly after the last time
* at which a queue either entered the burst list or was marked as
* belonging to the current large burst, then Q is immediately marked
* as belonging to a large burst.
*
* . if a queue Q that does not belong to the burst is created a while
* later, i.e., not shortly after, than the last time at which a queue
* either entered the burst list or was marked as belonging to the
* current large burst, then the current burst is deemed as finished and:
*
* . the large-burst mode is reset if set
*
* . the burst list is emptied
*
* . Q is inserted in the burst list, as Q may be the first queue
* in a possible new burst (then the burst list contains just Q
* after this step).
*/
static void bfq_handle_burst(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
/*
* If bfqq is already in the burst list or is part of a large
* burst, or finally has just been split, then there is
* nothing else to do.
*/
if (!hlist_unhashed(&bfqq->burst_list_node) ||
bfq_bfqq_in_large_burst(bfqq) ||
time_is_after_eq_jiffies(bfqq->split_time +
msecs_to_jiffies(10)))
return;
/*
* If bfqq's creation happens late enough, or bfqq belongs to
* a different group than the burst group, then the current
* burst is finished, and related data structures must be
* reset.
*
* In this respect, consider the special case where bfqq is
* the very first queue created after BFQ is selected for this
* device. In this case, last_ins_in_burst and
* burst_parent_entity are not yet significant when we get
* here. But it is easy to verify that, whether or not the
* following condition is true, bfqq will end up being
* inserted into the burst list. In particular the list will
* happen to contain only bfqq. And this is exactly what has
* to happen, as bfqq may be the first queue of the first
* burst.
*/
if (time_is_before_jiffies(bfqd->last_ins_in_burst +
bfqd->bfq_burst_interval) ||
bfqq->entity.parent != bfqd->burst_parent_entity) {
bfqd->large_burst = false;
bfq_reset_burst_list(bfqd, bfqq);
goto end;
}
/*
* If we get here, then bfqq is being activated shortly after the
* last queue. So, if the current burst is also large, we can mark
* bfqq as belonging to this large burst immediately.
*/
if (bfqd->large_burst) {
bfq_mark_bfqq_in_large_burst(bfqq);
goto end;
}
/*
* If we get here, then a large-burst state has not yet been
* reached, but bfqq is being activated shortly after the last
* queue. Then we add bfqq to the burst.
*/
bfq_add_to_burst(bfqd, bfqq);
end:
/*
* At this point, bfqq either has been added to the current
* burst or has caused the current burst to terminate and a
* possible new burst to start. In particular, in the second
* case, bfqq has become the first queue in the possible new
* burst. In both cases last_ins_in_burst needs to be moved
* forward.
*/
bfqd->last_ins_in_burst = jiffies;
}
static int bfq_bfqq_budget_left(struct bfq_queue *bfqq)
{
struct bfq_entity *entity = &bfqq->entity;
return entity->budget - entity->service;
}
/*
* If enough samples have been computed, return the current max budget
* stored in bfqd, which is dynamically updated according to the
* estimated disk peak rate; otherwise return the default max budget
*/
static int bfq_max_budget(struct bfq_data *bfqd)
{
if (bfqd->budgets_assigned < bfq_stats_min_budgets)
return bfq_default_max_budget;
else
return bfqd->bfq_max_budget;
}
/*
* Return min budget, which is a fraction of the current or default
* max budget (trying with 1/32)
*/
static int bfq_min_budget(struct bfq_data *bfqd)
{
if (bfqd->budgets_assigned < bfq_stats_min_budgets)
return bfq_default_max_budget / 32;
else
return bfqd->bfq_max_budget / 32;
}
static void bfq_bfqq_expire(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
bool compensate,
enum bfqq_expiration reason);
/*
* The next function, invoked after the input queue bfqq switches from
* idle to busy, updates the budget of bfqq. The function also tells
* whether the in-service queue should be expired, by returning
* true. The purpose of expiring the in-service queue is to give bfqq
* the chance to possibly preempt the in-service queue, and the reason
* for preempting the in-service queue is to achieve one of the two
* goals below.
*
* 1. Guarantee to bfqq its reserved bandwidth even if bfqq has
* expired because it has remained idle. In particular, bfqq may have
* expired for one of the following two reasons:
*
* - BFQQE_NO_MORE_REQUESTS bfqq did not enjoy any device idling
* and did not make it to issue a new request before its last
* request was served;
*
* - BFQQE_TOO_IDLE bfqq did enjoy device idling, but did not issue
* a new request before the expiration of the idling-time.
*
* Even if bfqq has expired for one of the above reasons, the process
* associated with the queue may be however issuing requests greedily,
* and thus be sensitive to the bandwidth it receives (bfqq may have
* remained idle for other reasons: CPU high load, bfqq not enjoying
* idling, I/O throttling somewhere in the path from the process to
* the I/O scheduler, ...). But if, after every expiration for one of
* the above two reasons, bfqq has to wait for the service of at least
* one full budget of another queue before being served again, then
* bfqq is likely to get a much lower bandwidth or resource time than
* its reserved ones. To address this issue, two countermeasures need
* to be taken.
*
* First, the budget and the timestamps of bfqq need to be updated in
* a special way on bfqq reactivation: they need to be updated as if
* bfqq did not remain idle and did not expire. In fact, if they are
* computed as if bfqq expired and remained idle until reactivation,
* then the process associated with bfqq is treated as if, instead of
* being greedy, it stopped issuing requests when bfqq remained idle,
* and restarts issuing requests only on this reactivation. In other
* words, the scheduler does not help the process recover the "service
* hole" between bfqq expiration and reactivation. As a consequence,
* the process receives a lower bandwidth than its reserved one. In
* contrast, to recover this hole, the budget must be updated as if
* bfqq was not expired at all before this reactivation, i.e., it must
* be set to the value of the remaining budget when bfqq was
* expired. Along the same line, timestamps need to be assigned the
* value they had the last time bfqq was selected for service, i.e.,
* before last expiration. Thus timestamps need to be back-shifted
* with respect to their normal computation (see [1] for more details
* on this tricky aspect).
*
* Secondly, to allow the process to recover the hole, the in-service
* queue must be expired too, to give bfqq the chance to preempt it
* immediately. In fact, if bfqq has to wait for a full budget of the
* in-service queue to be completed, then it may become impossible to
* let the process recover the hole, even if the back-shifted
* timestamps of bfqq are lower than those of the in-service queue. If
* this happens for most or all of the holes, then the process may not
* receive its reserved bandwidth. In this respect, it is worth noting
* that, being the service of outstanding requests unpreemptible, a
* little fraction of the holes may however be unrecoverable, thereby
* causing a little loss of bandwidth.
*
* The last important point is detecting whether bfqq does need this
* bandwidth recovery. In this respect, the next function deems the
* process associated with bfqq greedy, and thus allows it to recover
* the hole, if: 1) the process is waiting for the arrival of a new
* request (which implies that bfqq expired for one of the above two
* reasons), and 2) such a request has arrived soon. The first
* condition is controlled through the flag non_blocking_wait_rq,
* while the second through the flag arrived_in_time. If both
* conditions hold, then the function computes the budget in the
* above-described special way, and signals that the in-service queue
* should be expired. Timestamp back-shifting is done later in
* __bfq_activate_entity.
*
* 2. Reduce latency. Even if timestamps are not backshifted to let
* the process associated with bfqq recover a service hole, bfqq may
* however happen to have, after being (re)activated, a lower finish
* timestamp than the in-service queue. That is, the next budget of
* bfqq may have to be completed before the one of the in-service
* queue. If this is the case, then preempting the in-service queue
* allows this goal to be achieved, apart from the unpreemptible,
* outstanding requests mentioned above.
*
* Unfortunately, regardless of which of the above two goals one wants
* to achieve, service trees need first to be updated to know whether
* the in-service queue must be preempted. To have service trees
* correctly updated, the in-service queue must be expired and
* rescheduled, and bfqq must be scheduled too. This is one of the
* most costly operations (in future versions, the scheduling
* mechanism may be re-designed in such a way to make it possible to
* know whether preemption is needed without needing to update service
* trees). In addition, queue preemptions almost always cause random
* I/O, and thus loss of throughput. Because of these facts, the next
* function adopts the following simple scheme to avoid both costly
* operations and too frequent preemptions: it requests the expiration
* of the in-service queue (unconditionally) only for queues that need
* to recover a hole, or that either are weight-raised or deserve to
* be weight-raised.
*/
static bool bfq_bfqq_update_budg_for_activation(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
bool arrived_in_time,
bool wr_or_deserves_wr)
{
struct bfq_entity *entity = &bfqq->entity;
if (bfq_bfqq_non_blocking_wait_rq(bfqq) && arrived_in_time) {
/*
* We do not clear the flag non_blocking_wait_rq here, as
* the latter is used in bfq_activate_bfqq to signal
* that timestamps need to be back-shifted (and is
* cleared right after).
*/
/*
* In next assignment we rely on that either
* entity->service or entity->budget are not updated
* on expiration if bfqq is empty (see
* __bfq_bfqq_recalc_budget). Thus both quantities
* remain unchanged after such an expiration, and the
* following statement therefore assigns to
* entity->budget the remaining budget on such an
* expiration. For clarity, entity->service is not
* updated on expiration in any case, and, in normal
* operation, is reset only when bfqq is selected for
* service (see bfq_get_next_queue).
*/
entity->budget = min_t(unsigned long,
bfq_bfqq_budget_left(bfqq),
bfqq->max_budget);
return true;
}
entity->budget = max_t(unsigned long, bfqq->max_budget,
bfq_serv_to_charge(bfqq->next_rq, bfqq));
bfq_clear_bfqq_non_blocking_wait_rq(bfqq);
return wr_or_deserves_wr;
}
static unsigned int bfq_wr_duration(struct bfq_data *bfqd)
{
u64 dur;
if (bfqd->bfq_wr_max_time > 0)
return bfqd->bfq_wr_max_time;
dur = bfqd->RT_prod;
do_div(dur, bfqd->peak_rate);
/*
* Limit duration between 3 and 13 seconds. Tests show that
* higher values than 13 seconds often yield the opposite of
* the desired result, i.e., worsen responsiveness by letting
* non-interactive and non-soft-real-time applications
* preserve weight raising for a too long time interval.
*
* On the other end, lower values than 3 seconds make it
* difficult for most interactive tasks to complete their jobs
* before weight-raising finishes.
*/
if (dur > msecs_to_jiffies(13000))
dur = msecs_to_jiffies(13000);
else if (dur < msecs_to_jiffies(3000))
dur = msecs_to_jiffies(3000);
return dur;
}
static void bfq_update_bfqq_wr_on_rq_arrival(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
unsigned int old_wr_coeff,
bool wr_or_deserves_wr,
bool interactive,
bool in_burst,
bool soft_rt)
{
if (old_wr_coeff == 1 && wr_or_deserves_wr) {
/* start a weight-raising period */
if (interactive) {
bfqq->wr_coeff = bfqd->bfq_wr_coeff;
bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
} else {
bfqq->wr_start_at_switch_to_srt = jiffies;
bfqq->wr_coeff = bfqd->bfq_wr_coeff *
BFQ_SOFTRT_WEIGHT_FACTOR;
bfqq->wr_cur_max_time =
bfqd->bfq_wr_rt_max_time;
}
/*
* If needed, further reduce budget to make sure it is
* close to bfqq's backlog, so as to reduce the
* scheduling-error component due to a too large
* budget. Do not care about throughput consequences,
* but only about latency. Finally, do not assign a
* too small budget either, to avoid increasing
* latency by causing too frequent expirations.
*/
bfqq->entity.budget = min_t(unsigned long,
bfqq->entity.budget,
2 * bfq_min_budget(bfqd));
} else if (old_wr_coeff > 1) {
if (interactive) { /* update wr coeff and duration */
bfqq->wr_coeff = bfqd->bfq_wr_coeff;
bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
} else if (in_burst)
bfqq->wr_coeff = 1;
else if (soft_rt) {
/*
* The application is now or still meeting the
* requirements for being deemed soft rt. We
* can then correctly and safely (re)charge
* the weight-raising duration for the
* application with the weight-raising
* duration for soft rt applications.
*
* In particular, doing this recharge now, i.e.,
* before the weight-raising period for the
* application finishes, reduces the probability
* of the following negative scenario:
* 1) the weight of a soft rt application is
* raised at startup (as for any newly
* created application),
* 2) since the application is not interactive,
* at a certain time weight-raising is
* stopped for the application,
* 3) at that time the application happens to
* still have pending requests, and hence
* is destined to not have a chance to be
* deemed soft rt before these requests are
* completed (see the comments to the
* function bfq_bfqq_softrt_next_start()
* for details on soft rt detection),
* 4) these pending requests experience a high
* latency because the application is not
* weight-raised while they are pending.
*/
if (bfqq->wr_cur_max_time !=
bfqd->bfq_wr_rt_max_time) {
bfqq->wr_start_at_switch_to_srt =
bfqq->last_wr_start_finish;
bfqq->wr_cur_max_time =
bfqd->bfq_wr_rt_max_time;
bfqq->wr_coeff = bfqd->bfq_wr_coeff *
BFQ_SOFTRT_WEIGHT_FACTOR;
}
bfqq->last_wr_start_finish = jiffies;
}
}
}
static bool bfq_bfqq_idle_for_long_time(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
return bfqq->dispatched == 0 &&
time_is_before_jiffies(
bfqq->budget_timeout +
bfqd->bfq_wr_min_idle_time);
}
static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
int old_wr_coeff,
struct request *rq,
bool *interactive)
{
bool soft_rt, in_burst, wr_or_deserves_wr,
bfqq_wants_to_preempt,
idle_for_long_time = bfq_bfqq_idle_for_long_time(bfqd, bfqq),
/*
* See the comments on
* bfq_bfqq_update_budg_for_activation for
* details on the usage of the next variable.
*/
arrived_in_time = ktime_get_ns() <=
bfqq->ttime.last_end_request +
bfqd->bfq_slice_idle * 3;
bfqg_stats_update_io_add(bfqq_group(RQ_BFQQ(rq)), bfqq, rq->cmd_flags);
/*
* bfqq deserves to be weight-raised if:
* - it is sync,
* - it does not belong to a large burst,
* - it has been idle for enough time or is soft real-time,
* - is linked to a bfq_io_cq (it is not shared in any sense).
*/
in_burst = bfq_bfqq_in_large_burst(bfqq);
soft_rt = bfqd->bfq_wr_max_softrt_rate > 0 &&
!in_burst &&
time_is_before_jiffies(bfqq->soft_rt_next_start);
*interactive = !in_burst && idle_for_long_time;
wr_or_deserves_wr = bfqd->low_latency &&
(bfqq->wr_coeff > 1 ||
(bfq_bfqq_sync(bfqq) &&
bfqq->bic && (*interactive || soft_rt)));
/*
* Using the last flag, update budget and check whether bfqq
* may want to preempt the in-service queue.
*/
bfqq_wants_to_preempt =
bfq_bfqq_update_budg_for_activation(bfqd, bfqq,
arrived_in_time,
wr_or_deserves_wr);
/*
* If bfqq happened to be activated in a burst, but has been
* idle for much more than an interactive queue, then we
* assume that, in the overall I/O initiated in the burst, the
* I/O associated with bfqq is finished. So bfqq does not need
* to be treated as a queue belonging to a burst
* anymore. Accordingly, we reset bfqq's in_large_burst flag
* if set, and remove bfqq from the burst list if it's
* there. We do not decrement burst_size, because the fact
* that bfqq does not need to belong to the burst list any
* more does not invalidate the fact that bfqq was created in
* a burst.
*/
if (likely(!bfq_bfqq_just_created(bfqq)) &&
idle_for_long_time &&
time_is_before_jiffies(
bfqq->budget_timeout +
msecs_to_jiffies(10000))) {
hlist_del_init(&bfqq->burst_list_node);
bfq_clear_bfqq_in_large_burst(bfqq);
}
bfq_clear_bfqq_just_created(bfqq);
if (!bfq_bfqq_IO_bound(bfqq)) {
if (arrived_in_time) {
bfqq->requests_within_timer++;
if (bfqq->requests_within_timer >=
bfqd->bfq_requests_within_timer)
bfq_mark_bfqq_IO_bound(bfqq);
} else
bfqq->requests_within_timer = 0;
}
if (bfqd->low_latency) {
if (unlikely(time_is_after_jiffies(bfqq->split_time)))
/* wraparound */
bfqq->split_time =
jiffies - bfqd->bfq_wr_min_idle_time - 1;
if (time_is_before_jiffies(bfqq->split_time +
bfqd->bfq_wr_min_idle_time)) {
bfq_update_bfqq_wr_on_rq_arrival(bfqd, bfqq,
old_wr_coeff,
wr_or_deserves_wr,
*interactive,
in_burst,
soft_rt);
if (old_wr_coeff != bfqq->wr_coeff)
bfqq->entity.prio_changed = 1;
}
}
bfqq->last_idle_bklogged = jiffies;
bfqq->service_from_backlogged = 0;
bfq_clear_bfqq_softrt_update(bfqq);
bfq_add_bfqq_busy(bfqd, bfqq);
/*
* Expire in-service queue only if preemption may be needed
* for guarantees. In this respect, the function
* next_queue_may_preempt just checks a simple, necessary
* condition, and not a sufficient condition based on
* timestamps. In fact, for the latter condition to be
* evaluated, timestamps would need first to be updated, and
* this operation is quite costly (see the comments on the
* function bfq_bfqq_update_budg_for_activation).
*/
if (bfqd->in_service_queue && bfqq_wants_to_preempt &&
bfqd->in_service_queue->wr_coeff < bfqq->wr_coeff &&
next_queue_may_preempt(bfqd))
bfq_bfqq_expire(bfqd, bfqd->in_service_queue,
false, BFQQE_PREEMPTED);
}
static void bfq_add_request(struct request *rq)
{
struct bfq_queue *bfqq = RQ_BFQQ(rq);
struct bfq_data *bfqd = bfqq->bfqd;
struct request *next_rq, *prev;
unsigned int old_wr_coeff = bfqq->wr_coeff;
bool interactive = false;
bfq_log_bfqq(bfqd, bfqq, "add_request %d", rq_is_sync(rq));
bfqq->queued[rq_is_sync(rq)]++;
bfqd->queued++;
elv_rb_add(&bfqq->sort_list, rq);
/*
* Check if this request is a better next-serve candidate.
*/
prev = bfqq->next_rq;
next_rq = bfq_choose_req(bfqd, bfqq->next_rq, rq, bfqd->last_position);
bfqq->next_rq = next_rq;
/*
* Adjust priority tree position, if next_rq changes.
*/
if (prev != bfqq->next_rq)
bfq_pos_tree_add_move(bfqd, bfqq);
if (!bfq_bfqq_busy(bfqq)) /* switching to busy ... */
bfq_bfqq_handle_idle_busy_switch(bfqd, bfqq, old_wr_coeff,
rq, &interactive);
else {
if (bfqd->low_latency && old_wr_coeff == 1 && !rq_is_sync(rq) &&
time_is_before_jiffies(
bfqq->last_wr_start_finish +
bfqd->bfq_wr_min_inter_arr_async)) {
bfqq->wr_coeff = bfqd->bfq_wr_coeff;
bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
bfqd->wr_busy_queues++;
bfqq->entity.prio_changed = 1;
}
if (prev != bfqq->next_rq)
bfq_updated_next_req(bfqd, bfqq);
}
/*
* Assign jiffies to last_wr_start_finish in the following
* cases:
*
* . if bfqq is not going to be weight-raised, because, for
* non weight-raised queues, last_wr_start_finish stores the
* arrival time of the last request; as of now, this piece
* of information is used only for deciding whether to
* weight-raise async queues
*
* . if bfqq is not weight-raised, because, if bfqq is now
* switching to weight-raised, then last_wr_start_finish
* stores the time when weight-raising starts
*
* . if bfqq is interactive, because, regardless of whether
* bfqq is currently weight-raised, the weight-raising
* period must start or restart (this case is considered
* separately because it is not detected by the above
* conditions, if bfqq is already weight-raised)
*
* last_wr_start_finish has to be updated also if bfqq is soft
* real-time, because the weight-raising period is constantly
* restarted on idle-to-busy transitions for these queues, but
* this is already done in bfq_bfqq_handle_idle_busy_switch if
* needed.
*/
if (bfqd->low_latency &&
(old_wr_coeff == 1 || bfqq->wr_coeff == 1 || interactive))
bfqq->last_wr_start_finish = jiffies;
}
static struct request *bfq_find_rq_fmerge(struct bfq_data *bfqd,
struct bio *bio,
struct request_queue *q)
{
struct bfq_queue *bfqq = bfqd->bio_bfqq;
if (bfqq)
return elv_rb_find(&bfqq->sort_list, bio_end_sector(bio));
return NULL;
}
static sector_t get_sdist(sector_t last_pos, struct request *rq)
{
if (last_pos)
return abs(blk_rq_pos(rq) - last_pos);
return 0;
}
#if 0 /* Still not clear if we can do without next two functions */
static void bfq_activate_request(struct request_queue *q, struct request *rq)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
bfqd->rq_in_driver++;
}
static void bfq_deactivate_request(struct request_queue *q, struct request *rq)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
bfqd->rq_in_driver--;
}
#endif
static void bfq_remove_request(struct request_queue *q,
struct request *rq)
{
struct bfq_queue *bfqq = RQ_BFQQ(rq);
struct bfq_data *bfqd = bfqq->bfqd;
const int sync = rq_is_sync(rq);
if (bfqq->next_rq == rq) {
bfqq->next_rq = bfq_find_next_rq(bfqd, bfqq, rq);
bfq_updated_next_req(bfqd, bfqq);
}
if (rq->queuelist.prev != &rq->queuelist)
list_del_init(&rq->queuelist);
bfqq->queued[sync]--;
bfqd->queued--;
elv_rb_del(&bfqq->sort_list, rq);
elv_rqhash_del(q, rq);
if (q->last_merge == rq)
q->last_merge = NULL;
if (RB_EMPTY_ROOT(&bfqq->sort_list)) {
bfqq->next_rq = NULL;
if (bfq_bfqq_busy(bfqq) && bfqq != bfqd->in_service_queue) {
bfq_del_bfqq_busy(bfqd, bfqq, false);
/*
* bfqq emptied. In normal operation, when
* bfqq is empty, bfqq->entity.service and
* bfqq->entity.budget must contain,
* respectively, the service received and the
* budget used last time bfqq emptied. These
* facts do not hold in this case, as at least
* this last removal occurred while bfqq is
* not in service. To avoid inconsistencies,
* reset both bfqq->entity.service and
* bfqq->entity.budget, if bfqq has still a
* process that may issue I/O requests to it.
*/
bfqq->entity.budget = bfqq->entity.service = 0;
}
/*
* Remove queue from request-position tree as it is empty.
*/
if (bfqq->pos_root) {
rb_erase(&bfqq->pos_node, bfqq->pos_root);
bfqq->pos_root = NULL;
}
}
if (rq->cmd_flags & REQ_META)
bfqq->meta_pending--;
bfqg_stats_update_io_remove(bfqq_group(bfqq), rq->cmd_flags);
}
static bool bfq_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
{
struct request_queue *q = hctx->queue;
struct bfq_data *bfqd = q->elevator->elevator_data;
struct request *free = NULL;
/*
* bfq_bic_lookup grabs the queue_lock: invoke it now and
* store its return value for later use, to avoid nesting
* queue_lock inside the bfqd->lock. We assume that the bic
* returned by bfq_bic_lookup does not go away before
* bfqd->lock is taken.
*/
struct bfq_io_cq *bic = bfq_bic_lookup(bfqd, current->io_context, q);
bool ret;
spin_lock_irq(&bfqd->lock);
if (bic)
bfqd->bio_bfqq = bic_to_bfqq(bic, op_is_sync(bio->bi_opf));
else
bfqd->bio_bfqq = NULL;
bfqd->bio_bic = bic;
ret = blk_mq_sched_try_merge(q, bio, &free);
if (free)
blk_mq_free_request(free);
spin_unlock_irq(&bfqd->lock);
return ret;
}
static int bfq_request_merge(struct request_queue *q, struct request **req,
struct bio *bio)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
struct request *__rq;
__rq = bfq_find_rq_fmerge(bfqd, bio, q);
if (__rq && elv_bio_merge_ok(__rq, bio)) {
*req = __rq;
return ELEVATOR_FRONT_MERGE;
}
return ELEVATOR_NO_MERGE;
}
static void bfq_request_merged(struct request_queue *q, struct request *req,
enum elv_merge type)
{
if (type == ELEVATOR_FRONT_MERGE &&
rb_prev(&req->rb_node) &&
blk_rq_pos(req) <
blk_rq_pos(container_of(rb_prev(&req->rb_node),
struct request, rb_node))) {
struct bfq_queue *bfqq = RQ_BFQQ(req);
struct bfq_data *bfqd = bfqq->bfqd;
struct request *prev, *next_rq;
/* Reposition request in its sort_list */
elv_rb_del(&bfqq->sort_list, req);
elv_rb_add(&bfqq->sort_list, req);
/* Choose next request to be served for bfqq */
prev = bfqq->next_rq;
next_rq = bfq_choose_req(bfqd, bfqq->next_rq, req,
bfqd->last_position);
bfqq->next_rq = next_rq;
/*
* If next_rq changes, update both the queue's budget to
* fit the new request and the queue's position in its
* rq_pos_tree.
*/
if (prev != bfqq->next_rq) {
bfq_updated_next_req(bfqd, bfqq);
bfq_pos_tree_add_move(bfqd, bfqq);
}
}
}
static void bfq_requests_merged(struct request_queue *q, struct request *rq,
struct request *next)
{
struct bfq_queue *bfqq = RQ_BFQQ(rq), *next_bfqq = RQ_BFQQ(next);
if (!RB_EMPTY_NODE(&rq->rb_node))
goto end;
spin_lock_irq(&bfqq->bfqd->lock);
/*
* If next and rq belong to the same bfq_queue and next is older
* than rq, then reposition rq in the fifo (by substituting next
* with rq). Otherwise, if next and rq belong to different
* bfq_queues, never reposition rq: in fact, we would have to
* reposition it with respect to next's position in its own fifo,
* which would most certainly be too expensive with respect to
* the benefits.
*/
if (bfqq == next_bfqq &&
!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
next->fifo_time < rq->fifo_time) {
list_del_init(&rq->queuelist);
list_replace_init(&next->queuelist, &rq->queuelist);
rq->fifo_time = next->fifo_time;
}
if (bfqq->next_rq == next)
bfqq->next_rq = rq;
bfq_remove_request(q, next);
spin_unlock_irq(&bfqq->bfqd->lock);
end:
bfqg_stats_update_io_merged(bfqq_group(bfqq), next->cmd_flags);
}
/* Must be called with bfqq != NULL */
static void bfq_bfqq_end_wr(struct bfq_queue *bfqq)
{
if (bfq_bfqq_busy(bfqq))
bfqq->bfqd->wr_busy_queues--;
bfqq->wr_coeff = 1;
bfqq->wr_cur_max_time = 0;
bfqq->last_wr_start_finish = jiffies;
/*
* Trigger a weight change on the next invocation of
* __bfq_entity_update_weight_prio.
*/
bfqq->entity.prio_changed = 1;
}
static void bfq_end_wr_async_queues(struct bfq_data *bfqd,
struct bfq_group *bfqg)
{
int i, j;
for (i = 0; i < 2; i++)
for (j = 0; j < IOPRIO_BE_NR; j++)
if (bfqg->async_bfqq[i][j])
bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]);
if (bfqg->async_idle_bfqq)
bfq_bfqq_end_wr(bfqg->async_idle_bfqq);
}
static void bfq_end_wr(struct bfq_data *bfqd)
{
struct bfq_queue *bfqq;
spin_lock_irq(&bfqd->lock);
list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list)
bfq_bfqq_end_wr(bfqq);
list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list)
bfq_bfqq_end_wr(bfqq);
bfq_end_wr_async(bfqd);
spin_unlock_irq(&bfqd->lock);
}
static sector_t bfq_io_struct_pos(void *io_struct, bool request)
{
if (request)
return blk_rq_pos(io_struct);
else
return ((struct bio *)io_struct)->bi_iter.bi_sector;
}
static int bfq_rq_close_to_sector(void *io_struct, bool request,
sector_t sector)
{
return abs(bfq_io_struct_pos(io_struct, request) - sector) <=
BFQQ_CLOSE_THR;
}
static struct bfq_queue *bfqq_find_close(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
sector_t sector)
{
struct rb_root *root = &bfq_bfqq_to_bfqg(bfqq)->rq_pos_tree;
struct rb_node *parent, *node;
struct bfq_queue *__bfqq;
if (RB_EMPTY_ROOT(root))
return NULL;
/*
* First, if we find a request starting at the end of the last
* request, choose it.
*/
__bfqq = bfq_rq_pos_tree_lookup(bfqd, root, sector, &parent, NULL);
if (__bfqq)
return __bfqq;
/*
* If the exact sector wasn't found, the parent of the NULL leaf
* will contain the closest sector (rq_pos_tree sorted by
* next_request position).
*/
__bfqq = rb_entry(parent, struct bfq_queue, pos_node);
if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector))
return __bfqq;
if (blk_rq_pos(__bfqq->next_rq) < sector)
node = rb_next(&__bfqq->pos_node);
else
node = rb_prev(&__bfqq->pos_node);
if (!node)
return NULL;
__bfqq = rb_entry(node, struct bfq_queue, pos_node);
if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector))
return __bfqq;
return NULL;
}
static struct bfq_queue *bfq_find_close_cooperator(struct bfq_data *bfqd,
struct bfq_queue *cur_bfqq,
sector_t sector)
{
struct bfq_queue *bfqq;
/*
* We shall notice if some of the queues are cooperating,
* e.g., working closely on the same area of the device. In
* that case, we can group them together and: 1) don't waste
* time idling, and 2) serve the union of their requests in
* the best possible order for throughput.
*/
bfqq = bfqq_find_close(bfqd, cur_bfqq, sector);
if (!bfqq || bfqq == cur_bfqq)
return NULL;
return bfqq;
}
static struct bfq_queue *
bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
{
int process_refs, new_process_refs;
struct bfq_queue *__bfqq;
/*
* If there are no process references on the new_bfqq, then it is
* unsafe to follow the ->new_bfqq chain as other bfqq's in the chain
* may have dropped their last reference (not just their last process
* reference).
*/
if (!bfqq_process_refs(new_bfqq))
return NULL;
/* Avoid a circular list and skip interim queue merges. */
while ((__bfqq = new_bfqq->new_bfqq)) {
if (__bfqq == bfqq)
return NULL;
new_bfqq = __bfqq;
}
process_refs = bfqq_process_refs(bfqq);
new_process_refs = bfqq_process_refs(new_bfqq);
/*
* If the process for the bfqq has gone away, there is no
* sense in merging the queues.
*/
if (process_refs == 0 || new_process_refs == 0)
return NULL;
bfq_log_bfqq(bfqq->bfqd, bfqq, "scheduling merge with queue %d",
new_bfqq->pid);
/*
* Merging is just a redirection: the requests of the process
* owning one of the two queues are redirected to the other queue.
* The latter queue, in its turn, is set as shared if this is the
* first time that the requests of some process are redirected to
* it.
*
* We redirect bfqq to new_bfqq and not the opposite, because we
* are in the context of the process owning bfqq, hence we have
* the io_cq of this process. So we can immediately configure this
* io_cq to redirect the requests of the process to new_bfqq.
*
* NOTE, even if new_bfqq coincides with the in-service queue, the
* io_cq of new_bfqq is not available, because, if the in-service
* queue is shared, bfqd->in_service_bic may not point to the
* io_cq of the in-service queue.
* Redirecting the requests of the process owning bfqq to the
* currently in-service queue is in any case the best option, as
* we feed the in-service queue with new requests close to the
* last request served and, by doing so, hopefully increase the
* throughput.
*/
bfqq->new_bfqq = new_bfqq;
new_bfqq->ref += process_refs;
return new_bfqq;
}
static bool bfq_may_be_close_cooperator(struct bfq_queue *bfqq,
struct bfq_queue *new_bfqq)
{
if (bfq_class_idle(bfqq) || bfq_class_idle(new_bfqq) ||
(bfqq->ioprio_class != new_bfqq->ioprio_class))
return false;
/*
* If either of the queues has already been detected as seeky,
* then merging it with the other queue is unlikely to lead to
* sequential I/O.
*/
if (BFQQ_SEEKY(bfqq) || BFQQ_SEEKY(new_bfqq))
return false;
/*
* Interleaved I/O is known to be done by (some) applications
* only for reads, so it does not make sense to merge async
* queues.
*/
if (!bfq_bfqq_sync(bfqq) || !bfq_bfqq_sync(new_bfqq))
return false;
return true;
}
/*
* If this function returns true, then bfqq cannot be merged. The idea
* is that true cooperation happens very early after processes start
* to do I/O. Usually, late cooperations are just accidental false
* positives. In case bfqq is weight-raised, such false positives
* would evidently degrade latency guarantees for bfqq.
*/
static bool wr_from_too_long(struct bfq_queue *bfqq)
{
return bfqq->wr_coeff > 1 &&
time_is_before_jiffies(bfqq->last_wr_start_finish +
msecs_to_jiffies(100));
}
/*
* Attempt to schedule a merge of bfqq with the currently in-service
* queue or with a close queue among the scheduled queues. Return
* NULL if no merge was scheduled, a pointer to the shared bfq_queue
* structure otherwise.
*
* The OOM queue is not allowed to participate to cooperation: in fact, since
* the requests temporarily redirected to the OOM queue could be redirected
* again to dedicated queues at any time, the state needed to correctly
* handle merging with the OOM queue would be quite complex and expensive
* to maintain. Besides, in such a critical condition as an out of memory,
* the benefits of queue merging may be little relevant, or even negligible.
*
* Weight-raised queues can be merged only if their weight-raising
* period has just started. In fact cooperating processes are usually
* started together. Thus, with this filter we avoid false positives
* that would jeopardize low-latency guarantees.
*
* WARNING: queue merging may impair fairness among non-weight raised
* queues, for at least two reasons: 1) the original weight of a
* merged queue may change during the merged state, 2) even being the
* weight the same, a merged queue may be bloated with many more
* requests than the ones produced by its originally-associated
* process.
*/
static struct bfq_queue *
bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
void *io_struct, bool request)
{
struct bfq_queue *in_service_bfqq, *new_bfqq;
if (bfqq->new_bfqq)
return bfqq->new_bfqq;
if (!io_struct ||
wr_from_too_long(bfqq) ||
unlikely(bfqq == &bfqd->oom_bfqq))
return NULL;
/* If there is only one backlogged queue, don't search. */
if (bfqd->busy_queues == 1)
return NULL;
in_service_bfqq = bfqd->in_service_queue;
if (!in_service_bfqq || in_service_bfqq == bfqq ||
!bfqd->in_service_bic || wr_from_too_long(in_service_bfqq) ||
unlikely(in_service_bfqq == &bfqd->oom_bfqq))
goto check_scheduled;
if (bfq_rq_close_to_sector(io_struct, request, bfqd->last_position) &&
bfqq->entity.parent == in_service_bfqq->entity.parent &&
bfq_may_be_close_cooperator(bfqq, in_service_bfqq)) {
new_bfqq = bfq_setup_merge(bfqq, in_service_bfqq);
if (new_bfqq)
return new_bfqq;
}
/*
* Check whether there is a cooperator among currently scheduled
* queues. The only thing we need is that the bio/request is not
* NULL, as we need it to establish whether a cooperator exists.
*/
check_scheduled:
new_bfqq = bfq_find_close_cooperator(bfqd, bfqq,
bfq_io_struct_pos(io_struct, request));
if (new_bfqq && !wr_from_too_long(new_bfqq) &&
likely(new_bfqq != &bfqd->oom_bfqq) &&
bfq_may_be_close_cooperator(bfqq, new_bfqq))
return bfq_setup_merge(bfqq, new_bfqq);
return NULL;
}
static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
{
struct bfq_io_cq *bic = bfqq->bic;
/*
* If !bfqq->bic, the queue is already shared or its requests
* have already been redirected to a shared queue; both idle window
* and weight raising state have already been saved. Do nothing.
*/
if (!bic)
return;
bic->saved_ttime = bfqq->ttime;
bic->saved_idle_window = bfq_bfqq_idle_window(bfqq);
bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq);
bic->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq);
bic->was_in_burst_list = !hlist_unhashed(&bfqq->burst_list_node);
bic->saved_wr_coeff = bfqq->wr_coeff;
bic->saved_wr_start_at_switch_to_srt = bfqq->wr_start_at_switch_to_srt;
bic->saved_last_wr_start_finish = bfqq->last_wr_start_finish;
bic->saved_wr_cur_max_time = bfqq->wr_cur_max_time;
}
static void bfq_get_bic_reference(struct bfq_queue *bfqq)
{
/*
* If bfqq->bic has a non-NULL value, the bic to which it belongs
* is about to begin using a shared bfq_queue.
*/
if (bfqq->bic)
atomic_long_inc(&bfqq->bic->icq.ioc->refcount);
}
static void
bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic,
struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
{
bfq_log_bfqq(bfqd, bfqq, "merging with queue %lu",
(unsigned long)new_bfqq->pid);
/* Save weight raising and idle window of the merged queues */
bfq_bfqq_save_state(bfqq);
bfq_bfqq_save_state(new_bfqq);
if (bfq_bfqq_IO_bound(bfqq))
bfq_mark_bfqq_IO_bound(new_bfqq);
bfq_clear_bfqq_IO_bound(bfqq);
/*
* If bfqq is weight-raised, then let new_bfqq inherit
* weight-raising. To reduce false positives, neglect the case
* where bfqq has just been created, but has not yet made it
* to be weight-raised (which may happen because EQM may merge
* bfqq even before bfq_add_request is executed for the first
* time for bfqq). Handling this case would however be very
* easy, thanks to the flag just_created.
*/
if (new_bfqq->wr_coeff == 1 && bfqq->wr_coeff > 1) {
new_bfqq->wr_coeff = bfqq->wr_coeff;
new_bfqq->wr_cur_max_time = bfqq->wr_cur_max_time;
new_bfqq->last_wr_start_finish = bfqq->last_wr_start_finish;
new_bfqq->wr_start_at_switch_to_srt =
bfqq->wr_start_at_switch_to_srt;
if (bfq_bfqq_busy(new_bfqq))
bfqd->wr_busy_queues++;
new_bfqq->entity.prio_changed = 1;
}
if (bfqq->wr_coeff > 1) { /* bfqq has given its wr to new_bfqq */
bfqq->wr_coeff = 1;
bfqq->entity.prio_changed = 1;
if (bfq_bfqq_busy(bfqq))
bfqd->wr_busy_queues--;
}
bfq_log_bfqq(bfqd, new_bfqq, "merge_bfqqs: wr_busy %d",
bfqd->wr_busy_queues);
/*
* Grab a reference to the bic, to prevent it from being destroyed
* before being possibly touched by a bfq_split_bfqq().
*/
bfq_get_bic_reference(bfqq);
bfq_get_bic_reference(new_bfqq);
/*
* Merge queues (that is, let bic redirect its requests to new_bfqq)
*/
bic_set_bfqq(bic, new_bfqq, 1);
bfq_mark_bfqq_coop(new_bfqq);
/*
* new_bfqq now belongs to at least two bics (it is a shared queue):
* set new_bfqq->bic to NULL. bfqq either:
* - does not belong to any bic any more, and hence bfqq->bic must
* be set to NULL, or
* - is a queue whose owning bics have already been redirected to a
* different queue, hence the queue is destined to not belong to
* any bic soon and bfqq->bic is already NULL (therefore the next
* assignment causes no harm).
*/
new_bfqq->bic = NULL;
bfqq->bic = NULL;
/* release process reference to bfqq */
bfq_put_queue(bfqq);
}
static bool bfq_allow_bio_merge(struct request_queue *q, struct request *rq,
struct bio *bio)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
bool is_sync = op_is_sync(bio->bi_opf);
struct bfq_queue *bfqq = bfqd->bio_bfqq, *new_bfqq;
/*
* Disallow merge of a sync bio into an async request.
*/
if (is_sync && !rq_is_sync(rq))
return false;
/*
* Lookup the bfqq that this bio will be queued with. Allow
* merge only if rq is queued there.
*/
if (!bfqq)
return false;
/*
* We take advantage of this function to perform an early merge
* of the queues of possible cooperating processes.
*/
new_bfqq = bfq_setup_cooperator(bfqd, bfqq, bio, false);
if (new_bfqq) {
/*
* bic still points to bfqq, then it has not yet been
* redirected to some other bfq_queue, and a queue
* merge beween bfqq and new_bfqq can be safely
* fulfillled, i.e., bic can be redirected to new_bfqq
* and bfqq can be put.
*/
bfq_merge_bfqqs(bfqd, bfqd->bio_bic, bfqq,
new_bfqq);
/*
* If we get here, bio will be queued into new_queue,
* so use new_bfqq to decide whether bio and rq can be
* merged.
*/
bfqq = new_bfqq;
/*
* Change also bqfd->bio_bfqq, as
* bfqd->bio_bic now points to new_bfqq, and
* this function may be invoked again (and then may
* use again bqfd->bio_bfqq).
*/
bfqd->bio_bfqq = bfqq;
}
return bfqq == RQ_BFQQ(rq);
}
/*
* Set the maximum time for the in-service queue to consume its
* budget. This prevents seeky processes from lowering the throughput.
* In practice, a time-slice service scheme is used with seeky
* processes.
*/
static void bfq_set_budget_timeout(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
unsigned int timeout_coeff;
if (bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time)
timeout_coeff = 1;
else
timeout_coeff = bfqq->entity.weight / bfqq->entity.orig_weight;
bfqd->last_budget_start = ktime_get();
bfqq->budget_timeout = jiffies +
bfqd->bfq_timeout * timeout_coeff;
}
static void __bfq_set_in_service_queue(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
if (bfqq) {
bfqg_stats_update_avg_queue_size(bfqq_group(bfqq));
bfq_clear_bfqq_fifo_expire(bfqq);
bfqd->budgets_assigned = (bfqd->budgets_assigned * 7 + 256) / 8;
if (time_is_before_jiffies(bfqq->last_wr_start_finish) &&
bfqq->wr_coeff > 1 &&
bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time &&
time_is_before_jiffies(bfqq->budget_timeout)) {
/*
* For soft real-time queues, move the start
* of the weight-raising period forward by the
* time the queue has not received any
* service. Otherwise, a relatively long
* service delay is likely to cause the
* weight-raising period of the queue to end,
* because of the short duration of the
* weight-raising period of a soft real-time
* queue. It is worth noting that this move
* is not so dangerous for the other queues,
* because soft real-time queues are not
* greedy.
*
* To not add a further variable, we use the
* overloaded field budget_timeout to
* determine for how long the queue has not
* received service, i.e., how much time has
* elapsed since the queue expired. However,
* this is a little imprecise, because
* budget_timeout is set to jiffies if bfqq
* not only expires, but also remains with no
* request.
*/
if (time_after(bfqq->budget_timeout,
bfqq->last_wr_start_finish))
bfqq->last_wr_start_finish +=
jiffies - bfqq->budget_timeout;
else
bfqq->last_wr_start_finish = jiffies;
}
bfq_set_budget_timeout(bfqd, bfqq);
bfq_log_bfqq(bfqd, bfqq,
"set_in_service_queue, cur-budget = %d",
bfqq->entity.budget);
}
bfqd->in_service_queue = bfqq;
}
/*
* Get and set a new queue for service.
*/
static struct bfq_queue *bfq_set_in_service_queue(struct bfq_data *bfqd)
{
struct bfq_queue *bfqq = bfq_get_next_queue(bfqd);
__bfq_set_in_service_queue(bfqd, bfqq);
return bfqq;
}
static void bfq_arm_slice_timer(struct bfq_data *bfqd)
{
struct bfq_queue *bfqq = bfqd->in_service_queue;
struct bfq_io_cq *bic;
u32 sl;
/* Processes have exited, don't wait. */
bic = bfqd->in_service_bic;
if (!bic || atomic_read(&bic->icq.ioc->active_ref) == 0)
return;
bfq_mark_bfqq_wait_request(bfqq);
/*
* We don't want to idle for seeks, but we do want to allow
* fair distribution of slice time for a process doing back-to-back
* seeks. So allow a little bit of time for him to submit a new rq.
*/
sl = bfqd->bfq_slice_idle;
/*
* Unless the queue is being weight-raised or the scenario is
* asymmetric, grant only minimum idle time if the queue
* is seeky. A long idling is preserved for a weight-raised
* queue, or, more in general, in an asymmetric scenario,
* because a long idling is needed for guaranteeing to a queue
* its reserved share of the throughput (in particular, it is
* needed if the queue has a higher weight than some other
* queue).
*/
if (BFQQ_SEEKY(bfqq) && bfqq->wr_coeff == 1 &&
bfq_symmetric_scenario(bfqd))
sl = min_t(u64, sl, BFQ_MIN_TT);
bfqd->last_idling_start = ktime_get();
hrtimer_start(&bfqd->idle_slice_timer, ns_to_ktime(sl),
HRTIMER_MODE_REL);
bfqg_stats_set_start_idle_time(bfqq_group(bfqq));
}
/*
* In autotuning mode, max_budget is dynamically recomputed as the
* amount of sectors transferred in timeout at the estimated peak
* rate. This enables BFQ to utilize a full timeslice with a full
* budget, even if the in-service queue is served at peak rate. And
* this maximises throughput with sequential workloads.
*/
static unsigned long bfq_calc_max_budget(struct bfq_data *bfqd)
{
return (u64)bfqd->peak_rate * USEC_PER_MSEC *
jiffies_to_msecs(bfqd->bfq_timeout)>>BFQ_RATE_SHIFT;
}
/*
* Update parameters related to throughput and responsiveness, as a
* function of the estimated peak rate. See comments on
* bfq_calc_max_budget(), and on T_slow and T_fast arrays.
*/
static void update_thr_responsiveness_params(struct bfq_data *bfqd)
{
int dev_type = blk_queue_nonrot(bfqd->queue);
if (bfqd->bfq_user_max_budget == 0)
bfqd->bfq_max_budget =
bfq_calc_max_budget(bfqd);
if (bfqd->device_speed == BFQ_BFQD_FAST &&
bfqd->peak_rate < device_speed_thresh[dev_type]) {
bfqd->device_speed = BFQ_BFQD_SLOW;
bfqd->RT_prod = R_slow[dev_type] *
T_slow[dev_type];
} else if (bfqd->device_speed == BFQ_BFQD_SLOW &&
bfqd->peak_rate > device_speed_thresh[dev_type]) {
bfqd->device_speed = BFQ_BFQD_FAST;
bfqd->RT_prod = R_fast[dev_type] *
T_fast[dev_type];
}
bfq_log(bfqd,
"dev_type %s dev_speed_class = %s (%llu sects/sec), thresh %llu setcs/sec",
dev_type == 0 ? "ROT" : "NONROT",
bfqd->device_speed == BFQ_BFQD_FAST ? "FAST" : "SLOW",
bfqd->device_speed == BFQ_BFQD_FAST ?
(USEC_PER_SEC*(u64)R_fast[dev_type])>>BFQ_RATE_SHIFT :
(USEC_PER_SEC*(u64)R_slow[dev_type])>>BFQ_RATE_SHIFT,
(USEC_PER_SEC*(u64)device_speed_thresh[dev_type])>>
BFQ_RATE_SHIFT);
}
static void bfq_reset_rate_computation(struct bfq_data *bfqd,
struct request *rq)
{
if (rq != NULL) { /* new rq dispatch now, reset accordingly */
bfqd->last_dispatch = bfqd->first_dispatch = ktime_get_ns();
bfqd->peak_rate_samples = 1;
bfqd->sequential_samples = 0;
bfqd->tot_sectors_dispatched = bfqd->last_rq_max_size =
blk_rq_sectors(rq);
} else /* no new rq dispatched, just reset the number of samples */
bfqd->peak_rate_samples = 0; /* full re-init on next disp. */
bfq_log(bfqd,
"reset_rate_computation at end, sample %u/%u tot_sects %llu",
bfqd->peak_rate_samples, bfqd->sequential_samples,
bfqd->tot_sectors_dispatched);
}
static void bfq_update_rate_reset(struct bfq_data *bfqd, struct request *rq)
{
u32 rate, weight, divisor;
/*
* For the convergence property to hold (see comments on
* bfq_update_peak_rate()) and for the assessment to be
* reliable, a minimum number of samples must be present, and
* a minimum amount of time must have elapsed. If not so, do
* not compute new rate. Just reset parameters, to get ready
* for a new evaluation attempt.
*/
if (bfqd->peak_rate_samples < BFQ_RATE_MIN_SAMPLES ||
bfqd->delta_from_first < BFQ_RATE_MIN_INTERVAL)
goto reset_computation;
/*
* If a new request completion has occurred after last
* dispatch, then, to approximate the rate at which requests
* have been served by the device, it is more precise to
* extend the observation interval to the last completion.
*/
bfqd->delta_from_first =
max_t(u64, bfqd->delta_from_first,
bfqd->last_completion - bfqd->first_dispatch);
/*
* Rate computed in sects/usec, and not sects/nsec, for
* precision issues.
*/
rate = div64_ul(bfqd->tot_sectors_dispatched<<BFQ_RATE_SHIFT,
div_u64(bfqd->delta_from_first, NSEC_PER_USEC));
/*
* Peak rate not updated if:
* - the percentage of sequential dispatches is below 3/4 of the
* total, and rate is below the current estimated peak rate
* - rate is unreasonably high (> 20M sectors/sec)
*/
if ((bfqd->sequential_samples < (3 * bfqd->peak_rate_samples)>>2 &&
rate <= bfqd->peak_rate) ||
rate > 20<<BFQ_RATE_SHIFT)
goto reset_computation;
/*
* We have to update the peak rate, at last! To this purpose,
* we use a low-pass filter. We compute the smoothing constant
* of the filter as a function of the 'weight' of the new
* measured rate.
*
* As can be seen in next formulas, we define this weight as a
* quantity proportional to how sequential the workload is,
* and to how long the observation time interval is.
*
* The weight runs from 0 to 8. The maximum value of the
* weight, 8, yields the minimum value for the smoothing
* constant. At this minimum value for the smoothing constant,
* the measured rate contributes for half of the next value of
* the estimated peak rate.
*
* So, the first step is to compute the weight as a function
* of how sequential the workload is. Note that the weight
* cannot reach 9, because bfqd->sequential_samples cannot
* become equal to bfqd->peak_rate_samples, which, in its
* turn, holds true because bfqd->sequential_samples is not
* incremented for the first sample.
*/
weight = (9 * bfqd->sequential_samples) / bfqd->peak_rate_samples;
/*
* Second step: further refine the weight as a function of the
* duration of the observation interval.
*/
weight = min_t(u32, 8,
div_u64(weight * bfqd->delta_from_first,
BFQ_RATE_REF_INTERVAL));
/*
* Divisor ranging from 10, for minimum weight, to 2, for
* maximum weight.
*/
divisor = 10 - weight;
/*
* Finally, update peak rate:
*
* peak_rate = peak_rate * (divisor-1) / divisor + rate / divisor
*/
bfqd->peak_rate *= divisor-1;
bfqd->peak_rate /= divisor;
rate /= divisor; /* smoothing constant alpha = 1/divisor */
bfqd->peak_rate += rate;
update_thr_responsiveness_params(bfqd);
reset_computation:
bfq_reset_rate_computation(bfqd, rq);
}
/*
* Update the read/write peak rate (the main quantity used for
* auto-tuning, see update_thr_responsiveness_params()).
*
* It is not trivial to estimate the peak rate (correctly): because of
* the presence of sw and hw queues between the scheduler and the
* device components that finally serve I/O requests, it is hard to
* say exactly when a given dispatched request is served inside the
* device, and for how long. As a consequence, it is hard to know
* precisely at what rate a given set of requests is actually served
* by the device.
*
* On the opposite end, the dispatch time of any request is trivially
* available, and, from this piece of information, the "dispatch rate"
* of requests can be immediately computed. So, the idea in the next
* function is to use what is known, namely request dispatch times
* (plus, when useful, request completion times), to estimate what is
* unknown, namely in-device request service rate.
*
* The main issue is that, because of the above facts, the rate at
* which a certain set of requests is dispatched over a certain time
* interval can vary greatly with respect to the rate at which the
* same requests are then served. But, since the size of any
* intermediate queue is limited, and the service scheme is lossless
* (no request is silently dropped), the following obvious convergence
* property holds: the number of requests dispatched MUST become
* closer and closer to the number of requests completed as the
* observation interval grows. This is the key property used in
* the next function to estimate the peak service rate as a function
* of the observed dispatch rate. The function assumes to be invoked
* on every request dispatch.
*/
static void bfq_update_peak_rate(struct bfq_data *bfqd, struct request *rq)
{
u64 now_ns = ktime_get_ns();
if (bfqd->peak_rate_samples == 0) { /* first dispatch */
bfq_log(bfqd, "update_peak_rate: goto reset, samples %d",
bfqd->peak_rate_samples);
bfq_reset_rate_computation(bfqd, rq);
goto update_last_values; /* will add one sample */
}
/*
* Device idle for very long: the observation interval lasting
* up to this dispatch cannot be a valid observation interval
* for computing a new peak rate (similarly to the late-
* completion event in bfq_completed_request()). Go to
* update_rate_and_reset to have the following three steps
* taken:
* - close the observation interval at the last (previous)
* request dispatch or completion
* - compute rate, if possible, for that observation interval
* - start a new observation interval with this dispatch
*/
if (now_ns - bfqd->last_dispatch > 100*NSEC_PER_MSEC &&
bfqd->rq_in_driver == 0)
goto update_rate_and_reset;
/* Update sampling information */
bfqd->peak_rate_samples++;
if ((bfqd->rq_in_driver > 0 ||
now_ns - bfqd->last_completion < BFQ_MIN_TT)
&& get_sdist(bfqd->last_position, rq) < BFQQ_SEEK_THR)
bfqd->sequential_samples++;
bfqd->tot_sectors_dispatched += blk_rq_sectors(rq);
/* Reset max observed rq size every 32 dispatches */
if (likely(bfqd->peak_rate_samples % 32))
bfqd->last_rq_max_size =
max_t(u32, blk_rq_sectors(rq), bfqd->last_rq_max_size);
else
bfqd->last_rq_max_size = blk_rq_sectors(rq);
bfqd->delta_from_first = now_ns - bfqd->first_dispatch;
/* Target observation interval not yet reached, go on sampling */
if (bfqd->delta_from_first < BFQ_RATE_REF_INTERVAL)
goto update_last_values;
update_rate_and_reset:
bfq_update_rate_reset(bfqd, rq);
update_last_values:
bfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
bfqd->last_dispatch = now_ns;
}
/*
* Remove request from internal lists.
*/
static void bfq_dispatch_remove(struct request_queue *q, struct request *rq)
{
struct bfq_queue *bfqq = RQ_BFQQ(rq);
/*
* For consistency, the next instruction should have been
* executed after removing the request from the queue and
* dispatching it. We execute instead this instruction before
* bfq_remove_request() (and hence introduce a temporary
* inconsistency), for efficiency. In fact, should this
* dispatch occur for a non in-service bfqq, this anticipated
* increment prevents two counters related to bfqq->dispatched
* from risking to be, first, uselessly decremented, and then
* incremented again when the (new) value of bfqq->dispatched
* happens to be taken into account.
*/
bfqq->dispatched++;
bfq_update_peak_rate(q->elevator->elevator_data, rq);
bfq_remove_request(q, rq);
}
static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
/*
* If this bfqq is shared between multiple processes, check
* to make sure that those processes are still issuing I/Os
* within the mean seek distance. If not, it may be time to
* break the queues apart again.
*/
if (bfq_bfqq_coop(bfqq) && BFQQ_SEEKY(bfqq))
bfq_mark_bfqq_split_coop(bfqq);
if (RB_EMPTY_ROOT(&bfqq->sort_list)) {
if (bfqq->dispatched == 0)
/*
* Overloading budget_timeout field to store
* the time at which the queue remains with no
* backlog and no outstanding request; used by
* the weight-raising mechanism.
*/
bfqq->budget_timeout = jiffies;
bfq_del_bfqq_busy(bfqd, bfqq, true);
} else {
bfq_requeue_bfqq(bfqd, bfqq);
/*
* Resort priority tree of potential close cooperators.
*/
bfq_pos_tree_add_move(bfqd, bfqq);
}
/*
* All in-service entities must have been properly deactivated
* or requeued before executing the next function, which
* resets all in-service entites as no more in service.
*/
__bfq_bfqd_reset_in_service(bfqd);
}
/**
* __bfq_bfqq_recalc_budget - try to adapt the budget to the @bfqq behavior.
* @bfqd: device data.
* @bfqq: queue to update.
* @reason: reason for expiration.
*
* Handle the feedback on @bfqq budget at queue expiration.
* See the body for detailed comments.
*/
static void __bfq_bfqq_recalc_budget(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
enum bfqq_expiration reason)
{
struct request *next_rq;
int budget, min_budget;
min_budget = bfq_min_budget(bfqd);
if (bfqq->wr_coeff == 1)
budget = bfqq->max_budget;
else /*
* Use a constant, low budget for weight-raised queues,
* to help achieve a low latency. Keep it slightly higher
* than the minimum possible budget, to cause a little
* bit fewer expirations.
*/
budget = 2 * min_budget;
bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last budg %d, budg left %d",
bfqq->entity.budget, bfq_bfqq_budget_left(bfqq));
bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last max_budg %d, min budg %d",
budget, bfq_min_budget(bfqd));
bfq_log_bfqq(bfqd, bfqq, "recalc_budg: sync %d, seeky %d",
bfq_bfqq_sync(bfqq), BFQQ_SEEKY(bfqd->in_service_queue));
if (bfq_bfqq_sync(bfqq) && bfqq->wr_coeff == 1) {
switch (reason) {
/*
* Caveat: in all the following cases we trade latency
* for throughput.
*/
case BFQQE_TOO_IDLE:
/*
* This is the only case where we may reduce
* the budget: if there is no request of the
* process still waiting for completion, then
* we assume (tentatively) that the timer has
* expired because the batch of requests of
* the process could have been served with a
* smaller budget. Hence, betting that
* process will behave in the same way when it
* becomes backlogged again, we reduce its
* next budget. As long as we guess right,
* this budget cut reduces the latency
* experienced by the process.
*
* However, if there are still outstanding
* requests, then the process may have not yet
* issued its next request just because it is
* still waiting for the completion of some of
* the still outstanding ones. So in this
* subcase we do not reduce its budget, on the
* contrary we increase it to possibly boost
* the throughput, as discussed in the
* comments to the BUDGET_TIMEOUT case.
*/
if (bfqq->dispatched > 0) /* still outstanding reqs */
budget = min(budget * 2, bfqd->bfq_max_budget);
else {
if (budget > 5 * min_budget)
budget -= 4 * min_budget;
else
budget = min_budget;
}
break;
case BFQQE_BUDGET_TIMEOUT:
/*
* We double the budget here because it gives
* the chance to boost the throughput if this
* is not a seeky process (and has bumped into
* this timeout because of, e.g., ZBR).
*/
budget = min(budget * 2, bfqd->bfq_max_budget);
break;
case BFQQE_BUDGET_EXHAUSTED:
/*
* The process still has backlog, and did not
* let either the budget timeout or the disk
* idling timeout expire. Hence it is not
* seeky, has a short thinktime and may be
* happy with a higher budget too. So
* definitely increase the budget of this good
* candidate to boost the disk throughput.
*/
budget = min(budget * 4, bfqd->bfq_max_budget);
break;
case BFQQE_NO_MORE_REQUESTS:
/*
* For queues that expire for this reason, it
* is particularly important to keep the
* budget close to the actual service they
* need. Doing so reduces the timestamp
* misalignment problem described in the
* comments in the body of
* __bfq_activate_entity. In fact, suppose
* that a queue systematically expires for
* BFQQE_NO_MORE_REQUESTS and presents a
* new request in time to enjoy timestamp
* back-shifting. The larger the budget of the
* queue is with respect to the service the
* queue actually requests in each service
* slot, the more times the queue can be
* reactivated with the same virtual finish
* time. It follows that, even if this finish
* time is pushed to the system virtual time
* to reduce the consequent timestamp
* misalignment, the queue unjustly enjoys for
* many re-activations a lower finish time
* than all newly activated queues.
*
* The service needed by bfqq is measured
* quite precisely by bfqq->entity.service.
* Since bfqq does not enjoy device idling,
* bfqq->entity.service is equal to the number
* of sectors that the process associated with
* bfqq requested to read/write before waiting
* for request completions, or blocking for
* other reasons.
*/
budget = max_t(int, bfqq->entity.service, min_budget);
break;
default:
return;
}
} else if (!bfq_bfqq_sync(bfqq)) {
/*
* Async queues get always the maximum possible
* budget, as for them we do not care about latency
* (in addition, their ability to dispatch is limited
* by the charging factor).
*/
budget = bfqd->bfq_max_budget;
}
bfqq->max_budget = budget;
if (bfqd->budgets_assigned >= bfq_stats_min_budgets &&
!bfqd->bfq_user_max_budget)
bfqq->max_budget = min(bfqq->max_budget, bfqd->bfq_max_budget);
/*
* If there is still backlog, then assign a new budget, making
* sure that it is large enough for the next request. Since
* the finish time of bfqq must be kept in sync with the
* budget, be sure to call __bfq_bfqq_expire() *after* this
* update.
*
* If there is no backlog, then no need to update the budget;
* it will be updated on the arrival of a new request.
*/
next_rq = bfqq->next_rq;
if (next_rq)
bfqq->entity.budget = max_t(unsigned long, bfqq->max_budget,
bfq_serv_to_charge(next_rq, bfqq));
bfq_log_bfqq(bfqd, bfqq, "head sect: %u, new budget %d",
next_rq ? blk_rq_sectors(next_rq) : 0,
bfqq->entity.budget);
}
/*
* Return true if the process associated with bfqq is "slow". The slow
* flag is used, in addition to the budget timeout, to reduce the
* amount of service provided to seeky processes, and thus reduce
* their chances to lower the throughput. More details in the comments
* on the function bfq_bfqq_expire().
*
* An important observation is in order: as discussed in the comments
* on the function bfq_update_peak_rate(), with devices with internal
* queues, it is hard if ever possible to know when and for how long
* an I/O request is processed by the device (apart from the trivial
* I/O pattern where a new request is dispatched only after the
* previous one has been completed). This makes it hard to evaluate
* the real rate at which the I/O requests of each bfq_queue are
* served. In fact, for an I/O scheduler like BFQ, serving a
* bfq_queue means just dispatching its requests during its service
* slot (i.e., until the budget of the queue is exhausted, or the
* queue remains idle, or, finally, a timeout fires). But, during the
* service slot of a bfq_queue, around 100 ms at most, the device may
* be even still processing requests of bfq_queues served in previous
* service slots. On the opposite end, the requests of the in-service
* bfq_queue may be completed after the service slot of the queue
* finishes.
*
* Anyway, unless more sophisticated solutions are used
* (where possible), the sum of the sizes of the requests dispatched
* during the service slot of a bfq_queue is probably the only
* approximation available for the service received by the bfq_queue
* during its service slot. And this sum is the quantity used in this
* function to evaluate the I/O speed of a process.
*/
static bool bfq_bfqq_is_slow(struct bfq_data *bfqd, struct bfq_queue *bfqq,
bool compensate, enum bfqq_expiration reason,
unsigned long *delta_ms)
{
ktime_t delta_ktime;
u32 delta_usecs;
bool slow = BFQQ_SEEKY(bfqq); /* if delta too short, use seekyness */
if (!bfq_bfqq_sync(bfqq))
return false;
if (compensate)
delta_ktime = bfqd->last_idling_start;
else
delta_ktime = ktime_get();
delta_ktime = ktime_sub(delta_ktime, bfqd->last_budget_start);
delta_usecs = ktime_to_us(delta_ktime);
/* don't use too short time intervals */
if (delta_usecs < 1000) {
if (blk_queue_nonrot(bfqd->queue))
/*
* give same worst-case guarantees as idling
* for seeky
*/
*delta_ms = BFQ_MIN_TT / NSEC_PER_MSEC;
else /* charge at least one seek */
*delta_ms = bfq_slice_idle / NSEC_PER_MSEC;
return slow;
}
*delta_ms = delta_usecs / USEC_PER_MSEC;
/*
* Use only long (> 20ms) intervals to filter out excessive
* spikes in service rate estimation.
*/
if (delta_usecs > 20000) {
/*
* Caveat for rotational devices: processes doing I/O
* in the slower disk zones tend to be slow(er) even
* if not seeky. In this respect, the estimated peak
* rate is likely to be an average over the disk
* surface. Accordingly, to not be too harsh with
* unlucky processes, a process is deemed slow only if
* its rate has been lower than half of the estimated
* peak rate.
*/
slow = bfqq->entity.service < bfqd->bfq_max_budget / 2;
}
bfq_log_bfqq(bfqd, bfqq, "bfq_bfqq_is_slow: slow %d", slow);
return slow;
}
/*
* To be deemed as soft real-time, an application must meet two
* requirements. First, the application must not require an average
* bandwidth higher than the approximate bandwidth required to playback or
* record a compressed high-definition video.
* The next function is invoked on the completion of the last request of a
* batch, to compute the next-start time instant, soft_rt_next_start, such
* that, if the next request of the application does not arrive before
* soft_rt_next_start, then the above requirement on the bandwidth is met.
*
* The second requirement is that the request pattern of the application is
* isochronous, i.e., that, after issuing a request or a batch of requests,
* the application stops issuing new requests until all its pending requests
* have been completed. After that, the application may issue a new batch,
* and so on.
* For this reason the next function is invoked to compute
* soft_rt_next_start only for applications that meet this requirement,
* whereas soft_rt_next_start is set to infinity for applications that do
* not.
*
* Unfortunately, even a greedy application may happen to behave in an
* isochronous way if the CPU load is high. In fact, the application may
* stop issuing requests while the CPUs are busy serving other processes,
* then restart, then stop again for a while, and so on. In addition, if
* the disk achieves a low enough throughput with the request pattern
* issued by the application (e.g., because the request pattern is random
* and/or the device is slow), then the application may meet the above
* bandwidth requirement too. To prevent such a greedy application to be
* deemed as soft real-time, a further rule is used in the computation of
* soft_rt_next_start: soft_rt_next_start must be higher than the current
* time plus the maximum time for which the arrival of a request is waited
* for when a sync queue becomes idle, namely bfqd->bfq_slice_idle.
* This filters out greedy applications, as the latter issue instead their
* next request as soon as possible after the last one has been completed
* (in contrast, when a batch of requests is completed, a soft real-time
* application spends some time processing data).
*
* Unfortunately, the last filter may easily generate false positives if
* only bfqd->bfq_slice_idle is used as a reference time interval and one
* or both the following cases occur:
* 1) HZ is so low that the duration of a jiffy is comparable to or higher
* than bfqd->bfq_slice_idle. This happens, e.g., on slow devices with
* HZ=100.
* 2) jiffies, instead of increasing at a constant rate, may stop increasing
* for a while, then suddenly 'jump' by several units to recover the lost
* increments. This seems to happen, e.g., inside virtual machines.
* To address this issue, we do not use as a reference time interval just
* bfqd->bfq_slice_idle, but bfqd->bfq_slice_idle plus a few jiffies. In
* particular we add the minimum number of jiffies for which the filter
* seems to be quite precise also in embedded systems and KVM/QEMU virtual
* machines.
*/
static unsigned long bfq_bfqq_softrt_next_start(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
return max(bfqq->last_idle_bklogged +
HZ * bfqq->service_from_backlogged /
bfqd->bfq_wr_max_softrt_rate,
jiffies + nsecs_to_jiffies(bfqq->bfqd->bfq_slice_idle) + 4);
}
/*
* Return the farthest future time instant according to jiffies
* macros.
*/
static unsigned long bfq_greatest_from_now(void)
{
return jiffies + MAX_JIFFY_OFFSET;
}
/*
* Return the farthest past time instant according to jiffies
* macros.
*/
static unsigned long bfq_smallest_from_now(void)
{
return jiffies - MAX_JIFFY_OFFSET;
}
/**
* bfq_bfqq_expire - expire a queue.
* @bfqd: device owning the queue.
* @bfqq: the queue to expire.
* @compensate: if true, compensate for the time spent idling.
* @reason: the reason causing the expiration.
*
* If the process associated with bfqq does slow I/O (e.g., because it
* issues random requests), we charge bfqq with the time it has been
* in service instead of the service it has received (see
* bfq_bfqq_charge_time for details on how this goal is achieved). As
* a consequence, bfqq will typically get higher timestamps upon
* reactivation, and hence it will be rescheduled as if it had
* received more service than what it has actually received. In the
* end, bfqq receives less service in proportion to how slowly its
* associated process consumes its budgets (and hence how seriously it
* tends to lower the throughput). In addition, this time-charging
* strategy guarantees time fairness among slow processes. In
* contrast, if the process associated with bfqq is not slow, we
* charge bfqq exactly with the service it has received.
*
* Charging time to the first type of queues and the exact service to
* the other has the effect of using the WF2Q+ policy to schedule the
* former on a timeslice basis, without violating service domain
* guarantees among the latter.
*/
static void bfq_bfqq_expire(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
bool compensate,
enum bfqq_expiration reason)
{
bool slow;
unsigned long delta = 0;
struct bfq_entity *entity = &bfqq->entity;
int ref;
/*
* Check whether the process is slow (see bfq_bfqq_is_slow).
*/
slow = bfq_bfqq_is_slow(bfqd, bfqq, compensate, reason, &delta);
/*
* Increase service_from_backlogged before next statement,
* because the possible next invocation of
* bfq_bfqq_charge_time would likely inflate
* entity->service. In contrast, service_from_backlogged must
* contain real service, to enable the soft real-time
* heuristic to correctly compute the bandwidth consumed by
* bfqq.
*/
bfqq->service_from_backlogged += entity->service;
/*
* As above explained, charge slow (typically seeky) and
* timed-out queues with the time and not the service
* received, to favor sequential workloads.
*
* Processes doing I/O in the slower disk zones will tend to
* be slow(er) even if not seeky. Therefore, since the
* estimated peak rate is actually an average over the disk
* surface, these processes may timeout just for bad luck. To
* avoid punishing them, do not charge time to processes that
* succeeded in consuming at least 2/3 of their budget. This
* allows BFQ to preserve enough elasticity to still perform
* bandwidth, and not time, distribution with little unlucky
* or quasi-sequential processes.
*/
if (bfqq->wr_coeff == 1 &&
(slow ||
(reason == BFQQE_BUDGET_TIMEOUT &&
bfq_bfqq_budget_left(bfqq) >= entity->budget / 3)))
bfq_bfqq_charge_time(bfqd, bfqq, delta);
if (reason == BFQQE_TOO_IDLE &&
entity->service <= 2 * entity->budget / 10)
bfq_clear_bfqq_IO_bound(bfqq);
if (bfqd->low_latency && bfqq->wr_coeff == 1)
bfqq->last_wr_start_finish = jiffies;
if (bfqd->low_latency && bfqd->bfq_wr_max_softrt_rate > 0 &&
RB_EMPTY_ROOT(&bfqq->sort_list)) {
/*
* If we get here, and there are no outstanding
* requests, then the request pattern is isochronous
* (see the comments on the function
* bfq_bfqq_softrt_next_start()). Thus we can compute
* soft_rt_next_start. If, instead, the queue still
* has outstanding requests, then we have to wait for
* the completion of all the outstanding requests to
* discover whether the request pattern is actually
* isochronous.
*/
if (bfqq->dispatched == 0)
bfqq->soft_rt_next_start =
bfq_bfqq_softrt_next_start(bfqd, bfqq);
else {
/*
* The application is still waiting for the
* completion of one or more requests:
* prevent it from possibly being incorrectly
* deemed as soft real-time by setting its
* soft_rt_next_start to infinity. In fact,
* without this assignment, the application
* would be incorrectly deemed as soft
* real-time if:
* 1) it issued a new request before the
* completion of all its in-flight
* requests, and
* 2) at that time, its soft_rt_next_start
* happened to be in the past.
*/
bfqq->soft_rt_next_start =
bfq_greatest_from_now();
/*
* Schedule an update of soft_rt_next_start to when
* the task may be discovered to be isochronous.
*/
bfq_mark_bfqq_softrt_update(bfqq);
}
}
bfq_log_bfqq(bfqd, bfqq,
"expire (%d, slow %d, num_disp %d, idle_win %d)", reason,
slow, bfqq->dispatched, bfq_bfqq_idle_window(bfqq));
/*
* Increase, decrease or leave budget unchanged according to
* reason.
*/
__bfq_bfqq_recalc_budget(bfqd, bfqq, reason);
ref = bfqq->ref;
__bfq_bfqq_expire(bfqd, bfqq);
/* mark bfqq as waiting a request only if a bic still points to it */
if (ref > 1 && !bfq_bfqq_busy(bfqq) &&
reason != BFQQE_BUDGET_TIMEOUT &&
reason != BFQQE_BUDGET_EXHAUSTED)
bfq_mark_bfqq_non_blocking_wait_rq(bfqq);
}
/*
* Budget timeout is not implemented through a dedicated timer, but
* just checked on request arrivals and completions, as well as on
* idle timer expirations.
*/
static bool bfq_bfqq_budget_timeout(struct bfq_queue *bfqq)
{
return time_is_before_eq_jiffies(bfqq->budget_timeout);
}
/*
* If we expire a queue that is actively waiting (i.e., with the
* device idled) for the arrival of a new request, then we may incur
* the timestamp misalignment problem described in the body of the
* function __bfq_activate_entity. Hence we return true only if this
* condition does not hold, or if the queue is slow enough to deserve
* only to be kicked off for preserving a high throughput.
*/
static bool bfq_may_expire_for_budg_timeout(struct bfq_queue *bfqq)
{
bfq_log_bfqq(bfqq->bfqd, bfqq,
"may_budget_timeout: wait_request %d left %d timeout %d",
bfq_bfqq_wait_request(bfqq),
bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3,
bfq_bfqq_budget_timeout(bfqq));
return (!bfq_bfqq_wait_request(bfqq) ||
bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3)
&&
bfq_bfqq_budget_timeout(bfqq);
}
/*
* For a queue that becomes empty, device idling is allowed only if
* this function returns true for the queue. As a consequence, since
* device idling plays a critical role in both throughput boosting and
* service guarantees, the return value of this function plays a
* critical role in both these aspects as well.
*
* In a nutshell, this function returns true only if idling is
* beneficial for throughput or, even if detrimental for throughput,
* idling is however necessary to preserve service guarantees (low
* latency, desired throughput distribution, ...). In particular, on
* NCQ-capable devices, this function tries to return false, so as to
* help keep the drives' internal queues full, whenever this helps the
* device boost the throughput without causing any service-guarantee
* issue.
*
* In more detail, the return value of this function is obtained by,
* first, computing a number of boolean variables that take into
* account throughput and service-guarantee issues, and, then,
* combining these variables in a logical expression. Most of the
* issues taken into account are not trivial. We discuss these issues
* individually while introducing the variables.
*/
static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq)
{
struct bfq_data *bfqd = bfqq->bfqd;
bool idling_boosts_thr, idling_boosts_thr_without_issues,
idling_needed_for_service_guarantees,
asymmetric_scenario;
if (bfqd->strict_guarantees)
return true;
/*
* The next variable takes into account the cases where idling
* boosts the throughput.
*
* The value of the variable is computed considering, first, that
* idling is virtually always beneficial for the throughput if:
* (a) the device is not NCQ-capable, or
* (b) regardless of the presence of NCQ, the device is rotational
* and the request pattern for bfqq is I/O-bound and sequential.
*
* Secondly, and in contrast to the above item (b), idling an
* NCQ-capable flash-based device would not boost the
* throughput even with sequential I/O; rather it would lower
* the throughput in proportion to how fast the device
* is. Accordingly, the next variable is true if any of the
* above conditions (a) and (b) is true, and, in particular,
* happens to be false if bfqd is an NCQ-capable flash-based
* device.
*/
idling_boosts_thr = !bfqd->hw_tag ||
(!blk_queue_nonrot(bfqd->queue) && bfq_bfqq_IO_bound(bfqq) &&
bfq_bfqq_idle_window(bfqq));
/*
* The value of the next variable,
* idling_boosts_thr_without_issues, is equal to that of
* idling_boosts_thr, unless a special case holds. In this
* special case, described below, idling may cause problems to
* weight-raised queues.
*
* When the request pool is saturated (e.g., in the presence
* of write hogs), if the processes associated with
* non-weight-raised queues ask for requests at a lower rate,
* then processes associated with weight-raised queues have a
* higher probability to get a request from the pool
* immediately (or at least soon) when they need one. Thus
* they have a higher probability to actually get a fraction
* of the device throughput proportional to their high
* weight. This is especially true with NCQ-capable drives,
* which enqueue several requests in advance, and further
* reorder internally-queued requests.
*
* For this reason, we force to false the value of
* idling_boosts_thr_without_issues if there are weight-raised
* busy queues. In this case, and if bfqq is not weight-raised,
* this guarantees that the device is not idled for bfqq (if,
* instead, bfqq is weight-raised, then idling will be
* guaranteed by another variable, see below). Combined with
* the timestamping rules of BFQ (see [1] for details), this
* behavior causes bfqq, and hence any sync non-weight-raised
* queue, to get a lower number of requests served, and thus
* to ask for a lower number of requests from the request
* pool, before the busy weight-raised queues get served
* again. This often mitigates starvation problems in the
* presence of heavy write workloads and NCQ, thereby
* guaranteeing a higher application and system responsiveness
* in these hostile scenarios.
*/
idling_boosts_thr_without_issues = idling_boosts_thr &&
bfqd->wr_busy_queues == 0;
/*
* There is then a case where idling must be performed not
* for throughput concerns, but to preserve service
* guarantees.
*
* To introduce this case, we can note that allowing the drive
* to enqueue more than one request at a time, and hence
* delegating de facto final scheduling decisions to the
* drive's internal scheduler, entails loss of control on the
* actual request service order. In particular, the critical
* situation is when requests from different processes happen
* to be present, at the same time, in the internal queue(s)
* of the drive. In such a situation, the drive, by deciding
* the service order of the internally-queued requests, does
* determine also the actual throughput distribution among
* these processes. But the drive typically has no notion or
* concern about per-process throughput distribution, and
* makes its decisions only on a per-request basis. Therefore,
* the service distribution enforced by the drive's internal
* scheduler is likely to coincide with the desired
* device-throughput distribution only in a completely
* symmetric scenario where:
* (i) each of these processes must get the same throughput as
* the others;
* (ii) all these processes have the same I/O pattern
(either sequential or random).
* In fact, in such a scenario, the drive will tend to treat
* the requests of each of these processes in about the same
* way as the requests of the others, and thus to provide
* each of these processes with about the same throughput
* (which is exactly the desired throughput distribution). In
* contrast, in any asymmetric scenario, device idling is
* certainly needed to guarantee that bfqq receives its
* assigned fraction of the device throughput (see [1] for
* details).
*
* We address this issue by controlling, actually, only the
* symmetry sub-condition (i), i.e., provided that
* sub-condition (i) holds, idling is not performed,
* regardless of whether sub-condition (ii) holds. In other
* words, only if sub-condition (i) holds, then idling is
* allowed, and the device tends to be prevented from queueing
* many requests, possibly of several processes. The reason
* for not controlling also sub-condition (ii) is that we
* exploit preemption to preserve guarantees in case of
* symmetric scenarios, even if (ii) does not hold, as
* explained in the next two paragraphs.
*
* Even if a queue, say Q, is expired when it remains idle, Q
* can still preempt the new in-service queue if the next
* request of Q arrives soon (see the comments on
* bfq_bfqq_update_budg_for_activation). If all queues and
* groups have the same weight, this form of preemption,
* combined with the hole-recovery heuristic described in the
* comments on function bfq_bfqq_update_budg_for_activation,
* are enough to preserve a correct bandwidth distribution in
* the mid term, even without idling. In fact, even if not
* idling allows the internal queues of the device to contain
* many requests, and thus to reorder requests, we can rather
* safely assume that the internal scheduler still preserves a
* minimum of mid-term fairness. The motivation for using
* preemption instead of idling is that, by not idling,
* service guarantees are preserved without minimally
* sacrificing throughput. In other words, both a high
* throughput and its desired distribution are obtained.
*
* More precisely, this preemption-based, idleless approach
* provides fairness in terms of IOPS, and not sectors per
* second. This can be seen with a simple example. Suppose
* that there are two queues with the same weight, but that
* the first queue receives requests of 8 sectors, while the
* second queue receives requests of 1024 sectors. In
* addition, suppose that each of the two queues contains at
* most one request at a time, which implies that each queue
* always remains idle after it is served. Finally, after
* remaining idle, each queue receives very quickly a new
* request. It follows that the two queues are served
* alternatively, preempting each other if needed. This
* implies that, although both queues have the same weight,
* the queue with large requests receives a service that is
* 1024/8 times as high as the service received by the other
* queue.
*
* On the other hand, device idling is performed, and thus
* pure sector-domain guarantees are provided, for the
* following queues, which are likely to need stronger
* throughput guarantees: weight-raised queues, and queues
* with a higher weight than other queues. When such queues
* are active, sub-condition (i) is false, which triggers
* device idling.
*
* According to the above considerations, the next variable is
* true (only) if sub-condition (i) holds. To compute the
* value of this variable, we not only use the return value of
* the function bfq_symmetric_scenario(), but also check
* whether bfqq is being weight-raised, because
* bfq_symmetric_scenario() does not take into account also
* weight-raised queues (see comments on
* bfq_weights_tree_add()).
*
* As a side note, it is worth considering that the above
* device-idling countermeasures may however fail in the
* following unlucky scenario: if idling is (correctly)
* disabled in a time period during which all symmetry
* sub-conditions hold, and hence the device is allowed to
* enqueue many requests, but at some later point in time some
* sub-condition stops to hold, then it may become impossible
* to let requests be served in the desired order until all
* the requests already queued in the device have been served.
*/
asymmetric_scenario = bfqq->wr_coeff > 1 ||
!bfq_symmetric_scenario(bfqd);
/*
* Finally, there is a case where maximizing throughput is the
* best choice even if it may cause unfairness toward
* bfqq. Such a case is when bfqq became active in a burst of
* queue activations. Queues that became active during a large
* burst benefit only from throughput, as discussed in the
* comments on bfq_handle_burst. Thus, if bfqq became active
* in a burst and not idling the device maximizes throughput,
* then the device must no be idled, because not idling the
* device provides bfqq and all other queues in the burst with
* maximum benefit. Combining this and the above case, we can
* now establish when idling is actually needed to preserve
* service guarantees.
*/
idling_needed_for_service_guarantees =
asymmetric_scenario && !bfq_bfqq_in_large_burst(bfqq);
/*
* We have now all the components we need to compute the return
* value of the function, which is true only if both the following
* conditions hold:
* 1) bfqq is sync, because idling make sense only for sync queues;
* 2) idling either boosts the throughput (without issues), or
* is necessary to preserve service guarantees.
*/
return bfq_bfqq_sync(bfqq) &&
(idling_boosts_thr_without_issues ||
idling_needed_for_service_guarantees);
}
/*
* If the in-service queue is empty but the function bfq_bfqq_may_idle
* returns true, then:
* 1) the queue must remain in service and cannot be expired, and
* 2) the device must be idled to wait for the possible arrival of a new
* request for the queue.
* See the comments on the function bfq_bfqq_may_idle for the reasons
* why performing device idling is the best choice to boost the throughput
* and preserve service guarantees when bfq_bfqq_may_idle itself
* returns true.
*/
static bool bfq_bfqq_must_idle(struct bfq_queue *bfqq)
{
struct bfq_data *bfqd = bfqq->bfqd;
return RB_EMPTY_ROOT(&bfqq->sort_list) && bfqd->bfq_slice_idle != 0 &&
bfq_bfqq_may_idle(bfqq);
}
/*
* Select a queue for service. If we have a current queue in service,
* check whether to continue servicing it, or retrieve and set a new one.
*/
static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd)
{
struct bfq_queue *bfqq;
struct request *next_rq;
enum bfqq_expiration reason = BFQQE_BUDGET_TIMEOUT;
bfqq = bfqd->in_service_queue;
if (!bfqq)
goto new_queue;
bfq_log_bfqq(bfqd, bfqq, "select_queue: already in-service queue");
if (bfq_may_expire_for_budg_timeout(bfqq) &&
!bfq_bfqq_wait_request(bfqq) &&
!bfq_bfqq_must_idle(bfqq))
goto expire;
check_queue:
/*
* This loop is rarely executed more than once. Even when it
* happens, it is much more convenient to re-execute this loop
* than to return NULL and trigger a new dispatch to get a
* request served.
*/
next_rq = bfqq->next_rq;
/*
* If bfqq has requests queued and it has enough budget left to
* serve them, keep the queue, otherwise expire it.
*/
if (next_rq) {
if (bfq_serv_to_charge(next_rq, bfqq) >
bfq_bfqq_budget_left(bfqq)) {
/*
* Expire the queue for budget exhaustion,
* which makes sure that the next budget is
* enough to serve the next request, even if
* it comes from the fifo expired path.
*/
reason = BFQQE_BUDGET_EXHAUSTED;
goto expire;
} else {
/*
* The idle timer may be pending because we may
* not disable disk idling even when a new request
* arrives.
*/
if (bfq_bfqq_wait_request(bfqq)) {
/*
* If we get here: 1) at least a new request
* has arrived but we have not disabled the
* timer because the request was too small,
* 2) then the block layer has unplugged
* the device, causing the dispatch to be
* invoked.
*
* Since the device is unplugged, now the
* requests are probably large enough to
* provide a reasonable throughput.
* So we disable idling.
*/
bfq_clear_bfqq_wait_request(bfqq);
hrtimer_try_to_cancel(&bfqd->idle_slice_timer);
bfqg_stats_update_idle_time(bfqq_group(bfqq));
}
goto keep_queue;
}
}
/*
* No requests pending. However, if the in-service queue is idling
* for a new request, or has requests waiting for a completion and
* may idle after their completion, then keep it anyway.
*/
if (bfq_bfqq_wait_request(bfqq) ||
(bfqq->dispatched != 0 && bfq_bfqq_may_idle(bfqq))) {
bfqq = NULL;
goto keep_queue;
}
reason = BFQQE_NO_MORE_REQUESTS;
expire:
bfq_bfqq_expire(bfqd, bfqq, false, reason);
new_queue:
bfqq = bfq_set_in_service_queue(bfqd);
if (bfqq) {
bfq_log_bfqq(bfqd, bfqq, "select_queue: checking new queue");
goto check_queue;
}
keep_queue:
if (bfqq)
bfq_log_bfqq(bfqd, bfqq, "select_queue: returned this queue");
else
bfq_log(bfqd, "select_queue: no queue returned");
return bfqq;
}
static void bfq_update_wr_data(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
struct bfq_entity *entity = &bfqq->entity;
if (bfqq->wr_coeff > 1) { /* queue is being weight-raised */
bfq_log_bfqq(bfqd, bfqq,
"raising period dur %u/%u msec, old coeff %u, w %d(%d)",
jiffies_to_msecs(jiffies - bfqq->last_wr_start_finish),
jiffies_to_msecs(bfqq->wr_cur_max_time),
bfqq->wr_coeff,
bfqq->entity.weight, bfqq->entity.orig_weight);
if (entity->prio_changed)
bfq_log_bfqq(bfqd, bfqq, "WARN: pending prio change");
/*
* If the queue was activated in a burst, or too much
* time has elapsed from the beginning of this
* weight-raising period, then end weight raising.
*/
if (bfq_bfqq_in_large_burst(bfqq))
bfq_bfqq_end_wr(bfqq);
else if (time_is_before_jiffies(bfqq->last_wr_start_finish +
bfqq->wr_cur_max_time)) {
if (bfqq->wr_cur_max_time != bfqd->bfq_wr_rt_max_time ||
time_is_before_jiffies(bfqq->wr_start_at_switch_to_srt +
bfq_wr_duration(bfqd)))
bfq_bfqq_end_wr(bfqq);
else {
/* switch back to interactive wr */
bfqq->wr_coeff = bfqd->bfq_wr_coeff;
bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
bfqq->last_wr_start_finish =
bfqq->wr_start_at_switch_to_srt;
bfqq->entity.prio_changed = 1;
}
}
}
/* Update weight both if it must be raised and if it must be lowered */
if ((entity->weight > entity->orig_weight) != (bfqq->wr_coeff > 1))
__bfq_entity_update_weight_prio(
bfq_entity_service_tree(entity),
entity);
}
/*
* Dispatch next request from bfqq.
*/
static struct request *bfq_dispatch_rq_from_bfqq(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
struct request *rq = bfqq->next_rq;
unsigned long service_to_charge;
service_to_charge = bfq_serv_to_charge(rq, bfqq);
bfq_bfqq_served(bfqq, service_to_charge);
bfq_dispatch_remove(bfqd->queue, rq);
/*
* If weight raising has to terminate for bfqq, then next
* function causes an immediate update of bfqq's weight,
* without waiting for next activation. As a consequence, on
* expiration, bfqq will be timestamped as if has never been
* weight-raised during this service slot, even if it has
* received part or even most of the service as a
* weight-raised queue. This inflates bfqq's timestamps, which
* is beneficial, as bfqq is then more willing to leave the
* device immediately to possible other weight-raised queues.
*/
bfq_update_wr_data(bfqd, bfqq);
if (!bfqd->in_service_bic) {
atomic_long_inc(&RQ_BIC(rq)->icq.ioc->refcount);
bfqd->in_service_bic = RQ_BIC(rq);
}
/*
* Expire bfqq, pretending that its budget expired, if bfqq
* belongs to CLASS_IDLE and other queues are waiting for
* service.
*/
if (bfqd->busy_queues > 1 && bfq_class_idle(bfqq))
goto expire;
return rq;
expire:
bfq_bfqq_expire(bfqd, bfqq, false, BFQQE_BUDGET_EXHAUSTED);
return rq;
}
static bool bfq_has_work(struct blk_mq_hw_ctx *hctx)
{
struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
/*
* Avoiding lock: a race on bfqd->busy_queues should cause at
* most a call to dispatch for nothing
*/
return !list_empty_careful(&bfqd->dispatch) ||
bfqd->busy_queues > 0;
}
static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx)
{
struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
struct request *rq = NULL;
struct bfq_queue *bfqq = NULL;
if (!list_empty(&bfqd->dispatch)) {
rq = list_first_entry(&bfqd->dispatch, struct request,
queuelist);
list_del_init(&rq->queuelist);
bfqq = RQ_BFQQ(rq);
if (bfqq) {
/*
* Increment counters here, because this
* dispatch does not follow the standard
* dispatch flow (where counters are
* incremented)
*/
bfqq->dispatched++;
goto inc_in_driver_start_rq;
}
/*
* We exploit the put_rq_private hook to decrement
* rq_in_driver, but put_rq_private will not be
* invoked on this request. So, to avoid unbalance,
* just start this request, without incrementing
* rq_in_driver. As a negative consequence,
* rq_in_driver is deceptively lower than it should be
* while this request is in service. This may cause
* bfq_schedule_dispatch to be invoked uselessly.
*
* As for implementing an exact solution, the
* put_request hook, if defined, is probably invoked
* also on this request. So, by exploiting this hook,
* we could 1) increment rq_in_driver here, and 2)
* decrement it in put_request. Such a solution would
* let the value of the counter be always accurate,
* but it would entail using an extra interface
* function. This cost seems higher than the benefit,
* being the frequency of non-elevator-private
* requests very low.
*/
goto start_rq;
}
bfq_log(bfqd, "dispatch requests: %d busy queues", bfqd->busy_queues);
if (bfqd->busy_queues == 0)
goto exit;
/*
* Force device to serve one request at a time if
* strict_guarantees is true. Forcing this service scheme is
* currently the ONLY way to guarantee that the request
* service order enforced by the scheduler is respected by a
* queueing device. Otherwise the device is free even to make
* some unlucky request wait for as long as the device
* wishes.
*
* Of course, serving one request at at time may cause loss of
* throughput.
*/
if (bfqd->strict_guarantees && bfqd->rq_in_driver > 0)
goto exit;
bfqq = bfq_select_queue(bfqd);
if (!bfqq)
goto exit;
rq = bfq_dispatch_rq_from_bfqq(bfqd, bfqq);
if (rq) {
inc_in_driver_start_rq:
bfqd->rq_in_driver++;
start_rq:
rq->rq_flags |= RQF_STARTED;
}
exit:
return rq;
}
static struct request *bfq_dispatch_request(struct blk_mq_hw_ctx *hctx)
{
struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
struct request *rq;
spin_lock_irq(&bfqd->lock);
rq = __bfq_dispatch_request(hctx);
bfq_unlock_put_ioc(bfqd);
return rq;
}
/*
* Task holds one reference to the queue, dropped when task exits. Each rq
* in-flight on this queue also holds a reference, dropped when rq is freed.
*
* Scheduler lock must be held here. Recall not to use bfqq after calling
* this function on it.
*/
static void bfq_put_queue(struct bfq_queue *bfqq)
{
#ifdef CONFIG_BFQ_GROUP_IOSCHED
struct bfq_group *bfqg = bfqq_group(bfqq);
#endif
if (bfqq->bfqd)
bfq_log_bfqq(bfqq->bfqd, bfqq, "put_queue: %p %d",
bfqq, bfqq->ref);
bfqq->ref--;
if (bfqq->ref)
return;
if (bfq_bfqq_sync(bfqq))
/*
* The fact that this queue is being destroyed does not
* invalidate the fact that this queue may have been
* activated during the current burst. As a consequence,
* although the queue does not exist anymore, and hence
* needs to be removed from the burst list if there,
* the burst size has not to be decremented.
*/
hlist_del_init(&bfqq->burst_list_node);
kmem_cache_free(bfq_pool, bfqq);
#ifdef CONFIG_BFQ_GROUP_IOSCHED
bfqg_put(bfqg);
#endif
}
static void bfq_put_cooperator(struct bfq_queue *bfqq)
{
struct bfq_queue *__bfqq, *next;
/*
* If this queue was scheduled to merge with another queue, be
* sure to drop the reference taken on that queue (and others in
* the merge chain). See bfq_setup_merge and bfq_merge_bfqqs.
*/
__bfqq = bfqq->new_bfqq;
while (__bfqq) {
if (__bfqq == bfqq)
break;
next = __bfqq->new_bfqq;
bfq_put_queue(__bfqq);
__bfqq = next;
}
}
static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
if (bfqq == bfqd->in_service_queue) {
__bfq_bfqq_expire(bfqd, bfqq);
bfq_schedule_dispatch(bfqd);
}
bfq_log_bfqq(bfqd, bfqq, "exit_bfqq: %p, %d", bfqq, bfqq->ref);
bfq_put_cooperator(bfqq);
bfq_put_queue(bfqq); /* release process reference */
}
static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync)
{
struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync);
struct bfq_data *bfqd;
if (bfqq)
bfqd = bfqq->bfqd; /* NULL if scheduler already exited */
if (bfqq && bfqd) {
unsigned long flags;
spin_lock_irqsave(&bfqd->lock, flags);
/*
* If the bic is using a shared queue, put the
* reference taken on the io_context when the bic
* started using a shared bfq_queue. This put cannot
* make ioc->ref_count reach 0, then no ioc->lock
* risks to be taken (leading to possible deadlock
* scenarios).
*/
if (is_sync && bfq_bfqq_coop(bfqq))
put_io_context(bic->icq.ioc);
bfq_exit_bfqq(bfqd, bfqq);
bic_set_bfqq(bic, NULL, is_sync);
bfq_unlock_put_ioc_restore(bfqd, flags);
}
}
static void bfq_exit_icq(struct io_cq *icq)
{
struct bfq_io_cq *bic = icq_to_bic(icq);
bfq_exit_icq_bfqq(bic, true);
bfq_exit_icq_bfqq(bic, false);
}
/*
* Update the entity prio values; note that the new values will not
* be used until the next (re)activation.
*/
static void
bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
{
struct task_struct *tsk = current;
int ioprio_class;
struct bfq_data *bfqd = bfqq->bfqd;
if (!bfqd)
return;
ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio);
switch (ioprio_class) {
default:
dev_err(bfqq->bfqd->queue->backing_dev_info->dev,
"bfq: bad prio class %d\n", ioprio_class);
case IOPRIO_CLASS_NONE:
/*
* No prio set, inherit CPU scheduling settings.
*/
bfqq->new_ioprio = task_nice_ioprio(tsk);
bfqq->new_ioprio_class = task_nice_ioclass(tsk);
break;
case IOPRIO_CLASS_RT:
bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
bfqq->new_ioprio_class = IOPRIO_CLASS_RT;
break;
case IOPRIO_CLASS_BE:
bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
bfqq->new_ioprio_class = IOPRIO_CLASS_BE;
break;
case IOPRIO_CLASS_IDLE:
bfqq->new_ioprio_class = IOPRIO_CLASS_IDLE;
bfqq->new_ioprio = 7;
bfq_clear_bfqq_idle_window(bfqq);
break;
}
if (bfqq->new_ioprio >= IOPRIO_BE_NR) {
pr_crit("bfq_set_next_ioprio_data: new_ioprio %d\n",
bfqq->new_ioprio);
bfqq->new_ioprio = IOPRIO_BE_NR;
}
bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio);
bfqq->entity.prio_changed = 1;
}
static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio)
{
struct bfq_data *bfqd = bic_to_bfqd(bic);
struct bfq_queue *bfqq;
int ioprio = bic->icq.ioc->ioprio;
/*
* This condition may trigger on a newly created bic, be sure to
* drop the lock before returning.
*/
if (unlikely(!bfqd) || likely(bic->ioprio == ioprio))
return;
bic->ioprio = ioprio;
bfqq = bic_to_bfqq(bic, false);
if (bfqq) {
/* release process reference on this queue */
bfq_put_queue(bfqq);
bfqq = bfq_get_queue(bfqd, bio, BLK_RW_ASYNC, bic);
bic_set_bfqq(bic, bfqq, false);
}
bfqq = bic_to_bfqq(bic, true);
if (bfqq)
bfq_set_next_ioprio_data(bfqq, bic);
}
static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
struct bfq_io_cq *bic, pid_t pid, int is_sync)
{
RB_CLEAR_NODE(&bfqq->entity.rb_node);
INIT_LIST_HEAD(&bfqq->fifo);
INIT_HLIST_NODE(&bfqq->burst_list_node);
bfqq->ref = 0;
bfqq->bfqd = bfqd;
if (bic)
bfq_set_next_ioprio_data(bfqq, bic);
if (is_sync) {
if (!bfq_class_idle(bfqq))
bfq_mark_bfqq_idle_window(bfqq);
bfq_mark_bfqq_sync(bfqq);
bfq_mark_bfqq_just_created(bfqq);
} else
bfq_clear_bfqq_sync(bfqq);
/* set end request to minus infinity from now */
bfqq->ttime.last_end_request = ktime_get_ns() + 1;
bfq_mark_bfqq_IO_bound(bfqq);
bfqq->pid = pid;
/* Tentative initial value to trade off between thr and lat */
bfqq->max_budget = (2 * bfq_max_budget(bfqd)) / 3;
bfqq->budget_timeout = bfq_smallest_from_now();
bfqq->wr_coeff = 1;
bfqq->last_wr_start_finish = jiffies;
bfqq->wr_start_at_switch_to_srt = bfq_smallest_from_now();
bfqq->split_time = bfq_smallest_from_now();
/*
* Set to the value for which bfqq will not be deemed as
* soft rt when it becomes backlogged.
*/
bfqq->soft_rt_next_start = bfq_greatest_from_now();
/* first request is almost certainly seeky */
bfqq->seek_history = 1;
}
static struct bfq_queue **bfq_async_queue_prio(struct bfq_data *bfqd,
struct bfq_group *bfqg,
int ioprio_class, int ioprio)
{
switch (ioprio_class) {
case IOPRIO_CLASS_RT:
return &bfqg->async_bfqq[0][ioprio];
case IOPRIO_CLASS_NONE:
ioprio = IOPRIO_NORM;
/* fall through */
case IOPRIO_CLASS_BE:
return &bfqg->async_bfqq[1][ioprio];
case IOPRIO_CLASS_IDLE:
return &bfqg->async_idle_bfqq;
default:
return NULL;
}
}
static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,
struct bio *bio, bool is_sync,
struct bfq_io_cq *bic)
{
const int ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
const int ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio);
struct bfq_queue **async_bfqq = NULL;
struct bfq_queue *bfqq;
struct bfq_group *bfqg;
rcu_read_lock();
bfqg = bfq_find_set_group(bfqd, bio_blkcg(bio));
if (!bfqg) {
bfqq = &bfqd->oom_bfqq;
goto out;
}
if (!is_sync) {
async_bfqq = bfq_async_queue_prio(bfqd, bfqg, ioprio_class,
ioprio);
bfqq = *async_bfqq;
if (bfqq)
goto out;
}
bfqq = kmem_cache_alloc_node(bfq_pool,
GFP_NOWAIT | __GFP_ZERO | __GFP_NOWARN,
bfqd->queue->node);
if (bfqq) {
bfq_init_bfqq(bfqd, bfqq, bic, current->pid,
is_sync);
bfq_init_entity(&bfqq->entity, bfqg);
bfq_log_bfqq(bfqd, bfqq, "allocated");
} else {
bfqq = &bfqd->oom_bfqq;
bfq_log_bfqq(bfqd, bfqq, "using oom bfqq");
goto out;
}
/*
* Pin the queue now that it's allocated, scheduler exit will
* prune it.
*/
if (async_bfqq) {
bfqq->ref++; /*
* Extra group reference, w.r.t. sync
* queue. This extra reference is removed
* only if bfqq->bfqg disappears, to
* guarantee that this queue is not freed
* until its group goes away.
*/
bfq_log_bfqq(bfqd, bfqq, "get_queue, bfqq not in async: %p, %d",
bfqq, bfqq->ref);
*async_bfqq = bfqq;
}
out:
bfqq->ref++; /* get a process reference to this queue */
bfq_log_bfqq(bfqd, bfqq, "get_queue, at end: %p, %d", bfqq, bfqq->ref);
rcu_read_unlock();
return bfqq;
}
static void bfq_update_io_thinktime(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
struct bfq_ttime *ttime = &bfqq->ttime;
u64 elapsed = ktime_get_ns() - bfqq->ttime.last_end_request;
elapsed = min_t(u64, elapsed, 2ULL * bfqd->bfq_slice_idle);
ttime->ttime_samples = (7*bfqq->ttime.ttime_samples + 256) / 8;
ttime->ttime_total = div_u64(7*ttime->ttime_total + 256*elapsed, 8);
ttime->ttime_mean = div64_ul(ttime->ttime_total + 128,
ttime->ttime_samples);
}
static void
bfq_update_io_seektime(struct bfq_data *bfqd, struct bfq_queue *bfqq,
struct request *rq)
{
bfqq->seek_history <<= 1;
bfqq->seek_history |=
get_sdist(bfqq->last_request_pos, rq) > BFQQ_SEEK_THR &&
(!blk_queue_nonrot(bfqd->queue) ||
blk_rq_sectors(rq) < BFQQ_SECT_THR_NONROT);
}
/*
* Disable idle window if the process thinks too long or seeks so much that
* it doesn't matter.
*/
static void bfq_update_idle_window(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
struct bfq_io_cq *bic)
{
int enable_idle;
/* Don't idle for async or idle io prio class. */
if (!bfq_bfqq_sync(bfqq) || bfq_class_idle(bfqq))
return;
/* Idle window just restored, statistics are meaningless. */
if (time_is_after_eq_jiffies(bfqq->split_time +
bfqd->bfq_wr_min_idle_time))
return;
enable_idle = bfq_bfqq_idle_window(bfqq);
if (atomic_read(&bic->icq.ioc->active_ref) == 0 ||
bfqd->bfq_slice_idle == 0 ||
(bfqd->hw_tag && BFQQ_SEEKY(bfqq) &&
bfqq->wr_coeff == 1))
enable_idle = 0;
else if (bfq_sample_valid(bfqq->ttime.ttime_samples)) {
if (bfqq->ttime.ttime_mean > bfqd->bfq_slice_idle &&
bfqq->wr_coeff == 1)
enable_idle = 0;
else
enable_idle = 1;
}
bfq_log_bfqq(bfqd, bfqq, "update_idle_window: enable_idle %d",
enable_idle);
if (enable_idle)
bfq_mark_bfqq_idle_window(bfqq);
else
bfq_clear_bfqq_idle_window(bfqq);
}
/*
* Called when a new fs request (rq) is added to bfqq. Check if there's
* something we should do about it.
*/
static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq,
struct request *rq)
{
struct bfq_io_cq *bic = RQ_BIC(rq);
if (rq->cmd_flags & REQ_META)
bfqq->meta_pending++;
bfq_update_io_thinktime(bfqd, bfqq);
bfq_update_io_seektime(bfqd, bfqq, rq);
if (bfqq->entity.service > bfq_max_budget(bfqd) / 8 ||
!BFQQ_SEEKY(bfqq))
bfq_update_idle_window(bfqd, bfqq, bic);
bfq_log_bfqq(bfqd, bfqq,
"rq_enqueued: idle_window=%d (seeky %d)",
bfq_bfqq_idle_window(bfqq), BFQQ_SEEKY(bfqq));
bfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
if (bfqq == bfqd->in_service_queue && bfq_bfqq_wait_request(bfqq)) {
bool small_req = bfqq->queued[rq_is_sync(rq)] == 1 &&
blk_rq_sectors(rq) < 32;
bool budget_timeout = bfq_bfqq_budget_timeout(bfqq);
/*
* There is just this request queued: if the request
* is small and the queue is not to be expired, then
* just exit.
*
* In this way, if the device is being idled to wait
* for a new request from the in-service queue, we
* avoid unplugging the device and committing the
* device to serve just a small request. On the
* contrary, we wait for the block layer to decide
* when to unplug the device: hopefully, new requests
* will be merged to this one quickly, then the device
* will be unplugged and larger requests will be
* dispatched.
*/
if (small_req && !budget_timeout)
return;
/*
* A large enough request arrived, or the queue is to
* be expired: in both cases disk idling is to be
* stopped, so clear wait_request flag and reset
* timer.
*/
bfq_clear_bfqq_wait_request(bfqq);
hrtimer_try_to_cancel(&bfqd->idle_slice_timer);
bfqg_stats_update_idle_time(bfqq_group(bfqq));
/*
* The queue is not empty, because a new request just
* arrived. Hence we can safely expire the queue, in
* case of budget timeout, without risking that the
* timestamps of the queue are not updated correctly.
* See [1] for more details.
*/
if (budget_timeout)
bfq_bfqq_expire(bfqd, bfqq, false,
BFQQE_BUDGET_TIMEOUT);
}
}
static void __bfq_insert_request(struct bfq_data *bfqd, struct request *rq)
{
struct bfq_queue *bfqq = RQ_BFQQ(rq),
*new_bfqq = bfq_setup_cooperator(bfqd, bfqq, rq, true);
if (new_bfqq) {
if (bic_to_bfqq(RQ_BIC(rq), 1) != bfqq)
new_bfqq = bic_to_bfqq(RQ_BIC(rq), 1);
/*
* Release the request's reference to the old bfqq
* and make sure one is taken to the shared queue.
*/
new_bfqq->allocated++;
bfqq->allocated--;
new_bfqq->ref++;
bfq_clear_bfqq_just_created(bfqq);
/*
* If the bic associated with the process
* issuing this request still points to bfqq
* (and thus has not been already redirected
* to new_bfqq or even some other bfq_queue),
* then complete the merge and redirect it to
* new_bfqq.
*/
if (bic_to_bfqq(RQ_BIC(rq), 1) == bfqq)
bfq_merge_bfqqs(bfqd, RQ_BIC(rq),
bfqq, new_bfqq);
/*
* rq is about to be enqueued into new_bfqq,
* release rq reference on bfqq
*/
bfq_put_queue(bfqq);
rq->elv.priv[1] = new_bfqq;
bfqq = new_bfqq;
}
bfq_add_request(rq);
rq->fifo_time = ktime_get_ns() + bfqd->bfq_fifo_expire[rq_is_sync(rq)];
list_add_tail(&rq->queuelist, &bfqq->fifo);
bfq_rq_enqueued(bfqd, bfqq, rq);
}
static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
bool at_head)
{
struct request_queue *q = hctx->queue;
struct bfq_data *bfqd = q->elevator->elevator_data;
spin_lock_irq(&bfqd->lock);
if (blk_mq_sched_try_insert_merge(q, rq)) {
spin_unlock_irq(&bfqd->lock);
return;
}
spin_unlock_irq(&bfqd->lock);
blk_mq_sched_request_inserted(rq);
spin_lock_irq(&bfqd->lock);
if (at_head || blk_rq_is_passthrough(rq)) {
if (at_head)
list_add(&rq->queuelist, &bfqd->dispatch);
else
list_add_tail(&rq->queuelist, &bfqd->dispatch);
} else {
__bfq_insert_request(bfqd, rq);
if (rq_mergeable(rq)) {
elv_rqhash_add(q, rq);
if (!q->last_merge)
q->last_merge = rq;
}
}
bfq_unlock_put_ioc(bfqd);
}
static void bfq_insert_requests(struct blk_mq_hw_ctx *hctx,
struct list_head *list, bool at_head)
{
while (!list_empty(list)) {
struct request *rq;
rq = list_first_entry(list, struct request, queuelist);
list_del_init(&rq->queuelist);
bfq_insert_request(hctx, rq, at_head);
}
}
static void bfq_update_hw_tag(struct bfq_data *bfqd)
{
bfqd->max_rq_in_driver = max_t(int, bfqd->max_rq_in_driver,
bfqd->rq_in_driver);
if (bfqd->hw_tag == 1)
return;
/*
* This sample is valid if the number of outstanding requests
* is large enough to allow a queueing behavior. Note that the
* sum is not exact, as it's not taking into account deactivated
* requests.
*/
if (bfqd->rq_in_driver + bfqd->queued < BFQ_HW_QUEUE_THRESHOLD)
return;
if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES)
return;
bfqd->hw_tag = bfqd->max_rq_in_driver > BFQ_HW_QUEUE_THRESHOLD;
bfqd->max_rq_in_driver = 0;
bfqd->hw_tag_samples = 0;
}
static void bfq_completed_request(struct bfq_queue *bfqq, struct bfq_data *bfqd)
{
u64 now_ns;
u32 delta_us;
bfq_update_hw_tag(bfqd);
bfqd->rq_in_driver--;
bfqq->dispatched--;
if (!bfqq->dispatched && !bfq_bfqq_busy(bfqq)) {
/*
* Set budget_timeout (which we overload to store the
* time at which the queue remains with no backlog and
* no outstanding request; used by the weight-raising
* mechanism).
*/
bfqq->budget_timeout = jiffies;
bfq_weights_tree_remove(bfqd, &bfqq->entity,
&bfqd->queue_weights_tree);
}
now_ns = ktime_get_ns();
bfqq->ttime.last_end_request = now_ns;
/*
* Using us instead of ns, to get a reasonable precision in
* computing rate in next check.
*/
delta_us = div_u64(now_ns - bfqd->last_completion, NSEC_PER_USEC);
/*
* If the request took rather long to complete, and, according
* to the maximum request size recorded, this completion latency
* implies that the request was certainly served at a very low
* rate (less than 1M sectors/sec), then the whole observation
* interval that lasts up to this time instant cannot be a
* valid time interval for computing a new peak rate. Invoke
* bfq_update_rate_reset to have the following three steps
* taken:
* - close the observation interval at the last (previous)
* request dispatch or completion
* - compute rate, if possible, for that observation interval
* - reset to zero samples, which will trigger a proper
* re-initialization of the observation interval on next
* dispatch
*/
if (delta_us > BFQ_MIN_TT/NSEC_PER_USEC &&
(bfqd->last_rq_max_size<<BFQ_RATE_SHIFT)/delta_us <
1UL<<(BFQ_RATE_SHIFT - 10))
bfq_update_rate_reset(bfqd, NULL);
bfqd->last_completion = now_ns;
/*
* If we are waiting to discover whether the request pattern
* of the task associated with the queue is actually
* isochronous, and both requisites for this condition to hold
* are now satisfied, then compute soft_rt_next_start (see the
* comments on the function bfq_bfqq_softrt_next_start()). We
* schedule this delayed check when bfqq expires, if it still
* has in-flight requests.
*/
if (bfq_bfqq_softrt_update(bfqq) && bfqq->dispatched == 0 &&
RB_EMPTY_ROOT(&bfqq->sort_list))
bfqq->soft_rt_next_start =
bfq_bfqq_softrt_next_start(bfqd, bfqq);
/*
* If this is the in-service queue, check if it needs to be expired,
* or if we want to idle in case it has no pending requests.
*/
if (bfqd->in_service_queue == bfqq) {
if (bfqq->dispatched == 0 && bfq_bfqq_must_idle(bfqq)) {
bfq_arm_slice_timer(bfqd);
return;
} else if (bfq_may_expire_for_budg_timeout(bfqq))
bfq_bfqq_expire(bfqd, bfqq, false,
BFQQE_BUDGET_TIMEOUT);
else if (RB_EMPTY_ROOT(&bfqq->sort_list) &&
(bfqq->dispatched == 0 ||
!bfq_bfqq_may_idle(bfqq)))
bfq_bfqq_expire(bfqd, bfqq, false,
BFQQE_NO_MORE_REQUESTS);
}
}
static void bfq_put_rq_priv_body(struct bfq_queue *bfqq)
{
bfqq->allocated--;
bfq_put_queue(bfqq);
}
static void bfq_put_rq_private(struct request_queue *q, struct request *rq)
{
struct bfq_queue *bfqq = RQ_BFQQ(rq);
struct bfq_data *bfqd = bfqq->bfqd;
if (rq->rq_flags & RQF_STARTED)
bfqg_stats_update_completion(bfqq_group(bfqq),
rq_start_time_ns(rq),
rq_io_start_time_ns(rq),
rq->cmd_flags);
if (likely(rq->rq_flags & RQF_STARTED)) {
unsigned long flags;
spin_lock_irqsave(&bfqd->lock, flags);
bfq_completed_request(bfqq, bfqd);
bfq_put_rq_priv_body(bfqq);
bfq_unlock_put_ioc_restore(bfqd, flags);
} else {
/*
* Request rq may be still/already in the scheduler,
* in which case we need to remove it. And we cannot
* defer such a check and removal, to avoid
* inconsistencies in the time interval from the end
* of this function to the start of the deferred work.
* This situation seems to occur only in process
* context, as a consequence of a merge. In the
* current version of the code, this implies that the
* lock is held.
*/
if (!RB_EMPTY_NODE(&rq->rb_node))
bfq_remove_request(q, rq);
bfq_put_rq_priv_body(bfqq);
}
rq->elv.priv[0] = NULL;
rq->elv.priv[1] = NULL;
}
/*
* Returns NULL if a new bfqq should be allocated, or the old bfqq if this
* was the last process referring to that bfqq.
*/
static struct bfq_queue *
bfq_split_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq)
{
bfq_log_bfqq(bfqq->bfqd, bfqq, "splitting queue");
if (bfqq_process_refs(bfqq) == 1) {
bfqq->pid = current->pid;
bfq_clear_bfqq_coop(bfqq);
bfq_clear_bfqq_split_coop(bfqq);
return bfqq;
}
bic_set_bfqq(bic, NULL, 1);
bfq_put_cooperator(bfqq);
bfq_put_queue(bfqq);
return NULL;
}
static struct bfq_queue *bfq_get_bfqq_handle_split(struct bfq_data *bfqd,
struct bfq_io_cq *bic,
struct bio *bio,
bool split, bool is_sync,
bool *new_queue)
{
struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync);
if (likely(bfqq && bfqq != &bfqd->oom_bfqq))
return bfqq;
if (new_queue)
*new_queue = true;
if (bfqq)
bfq_put_queue(bfqq);
bfqq = bfq_get_queue(bfqd, bio, is_sync, bic);
bic_set_bfqq(bic, bfqq, is_sync);
if (split && is_sync) {
if ((bic->was_in_burst_list && bfqd->large_burst) ||
bic->saved_in_large_burst)
bfq_mark_bfqq_in_large_burst(bfqq);
else {
bfq_clear_bfqq_in_large_burst(bfqq);
if (bic->was_in_burst_list)
hlist_add_head(&bfqq->burst_list_node,
&bfqd->burst_list);
}
bfqq->split_time = jiffies;
}
return bfqq;
}
/*
* Allocate bfq data structures associated with this request.
*/
static int bfq_get_rq_private(struct request_queue *q, struct request *rq,
struct bio *bio)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
struct bfq_io_cq *bic = icq_to_bic(rq->elv.icq);
const int is_sync = rq_is_sync(rq);
struct bfq_queue *bfqq;
bool new_queue = false;
spin_lock_irq(&bfqd->lock);
bfq_check_ioprio_change(bic, bio);
if (!bic)
goto queue_fail;
bfq_bic_update_cgroup(bic, bio);
bfqq = bfq_get_bfqq_handle_split(bfqd, bic, bio, false, is_sync,
&new_queue);
if (likely(!new_queue)) {
/* If the queue was seeky for too long, break it apart. */
if (bfq_bfqq_coop(bfqq) && bfq_bfqq_split_coop(bfqq)) {
bfq_log_bfqq(bfqd, bfqq, "breaking apart bfqq");
/* Update bic before losing reference to bfqq */
if (bfq_bfqq_in_large_burst(bfqq))
bic->saved_in_large_burst = true;
bfqq = bfq_split_bfqq(bic, bfqq);
/*
* A reference to bic->icq.ioc needs to be
* released after a queue split. Do not do it
* immediately, to not risk to possibly take
* an ioc->lock while holding the scheduler
* lock.
*/
bfqd->ioc_to_put = bic->icq.ioc;
if (!bfqq)
bfqq = bfq_get_bfqq_handle_split(bfqd, bic, bio,
true, is_sync,
NULL);
}
}
bfqq->allocated++;
bfqq->ref++;
bfq_log_bfqq(bfqd, bfqq, "get_request %p: bfqq %p, %d",
rq, bfqq, bfqq->ref);
rq->elv.priv[0] = bic;
rq->elv.priv[1] = bfqq;
/*
* If a bfq_queue has only one process reference, it is owned
* by only this bic: we can then set bfqq->bic = bic. in
* addition, if the queue has also just been split, we have to
* resume its state.
*/
if (likely(bfqq != &bfqd->oom_bfqq) && bfqq_process_refs(bfqq) == 1) {
bfqq->bic = bic;
if (bfqd->ioc_to_put) { /* if true, there has been a split */
/*
* The queue has just been split from a shared
* queue: restore the idle window and the
* possible weight raising period.
*/
bfq_bfqq_resume_state(bfqq, bic);
}
}
if (unlikely(bfq_bfqq_just_created(bfqq)))
bfq_handle_burst(bfqd, bfqq);
bfq_unlock_put_ioc(bfqd);
return 0;
queue_fail:
spin_unlock_irq(&bfqd->lock);
return 1;
}
static void bfq_idle_slice_timer_body(struct bfq_queue *bfqq)
{
struct bfq_data *bfqd = bfqq->bfqd;
enum bfqq_expiration reason;
unsigned long flags;
spin_lock_irqsave(&bfqd->lock, flags);
bfq_clear_bfqq_wait_request(bfqq);
if (bfqq != bfqd->in_service_queue) {
spin_unlock_irqrestore(&bfqd->lock, flags);
return;
}
if (bfq_bfqq_budget_timeout(bfqq))
/*
* Also here the queue can be safely expired
* for budget timeout without wasting
* guarantees
*/
reason = BFQQE_BUDGET_TIMEOUT;
else if (bfqq->queued[0] == 0 && bfqq->queued[1] == 0)
/*
* The queue may not be empty upon timer expiration,
* because we may not disable the timer when the
* first request of the in-service queue arrives
* during disk idling.
*/
reason = BFQQE_TOO_IDLE;
else
goto schedule_dispatch;
bfq_bfqq_expire(bfqd, bfqq, true, reason);
schedule_dispatch:
bfq_unlock_put_ioc_restore(bfqd, flags);
bfq_schedule_dispatch(bfqd);
}
/*
* Handler of the expiration of the timer running if the in-service queue
* is idling inside its time slice.
*/
static enum hrtimer_restart bfq_idle_slice_timer(struct hrtimer *timer)
{
struct bfq_data *bfqd = container_of(timer, struct bfq_data,
idle_slice_timer);
struct bfq_queue *bfqq = bfqd->in_service_queue;
/*
* Theoretical race here: the in-service queue can be NULL or
* different from the queue that was idling if a new request
* arrives for the current queue and there is a full dispatch
* cycle that changes the in-service queue. This can hardly
* happen, but in the worst case we just expire a queue too
* early.
*/
if (bfqq)
bfq_idle_slice_timer_body(bfqq);
return HRTIMER_NORESTART;
}
static void __bfq_put_async_bfqq(struct bfq_data *bfqd,
struct bfq_queue **bfqq_ptr)
{
struct bfq_queue *bfqq = *bfqq_ptr;
bfq_log(bfqd, "put_async_bfqq: %p", bfqq);
if (bfqq) {
bfq_bfqq_move(bfqd, bfqq, bfqd->root_group);
bfq_log_bfqq(bfqd, bfqq, "put_async_bfqq: putting %p, %d",
bfqq, bfqq->ref);
bfq_put_queue(bfqq);
*bfqq_ptr = NULL;
}
}
/*
* Release all the bfqg references to its async queues. If we are
* deallocating the group these queues may still contain requests, so
* we reparent them to the root cgroup (i.e., the only one that will
* exist for sure until all the requests on a device are gone).
*/
static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
{
int i, j;
for (i = 0; i < 2; i++)
for (j = 0; j < IOPRIO_BE_NR; j++)
__bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]);
__bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq);
}
static void bfq_exit_queue(struct elevator_queue *e)
{
struct bfq_data *bfqd = e->elevator_data;
struct bfq_queue *bfqq, *n;
hrtimer_cancel(&bfqd->idle_slice_timer);
spin_lock_irq(&bfqd->lock);
list_for_each_entry_safe(bfqq, n, &bfqd->idle_list, bfqq_list)
bfq_deactivate_bfqq(bfqd, bfqq, false, false);
spin_unlock_irq(&bfqd->lock);
hrtimer_cancel(&bfqd->idle_slice_timer);
#ifdef CONFIG_BFQ_GROUP_IOSCHED
blkcg_deactivate_policy(bfqd->queue, &blkcg_policy_bfq);
#else
spin_lock_irq(&bfqd->lock);
bfq_put_async_queues(bfqd, bfqd->root_group);
kfree(bfqd->root_group);
spin_unlock_irq(&bfqd->lock);
#endif
kfree(bfqd);
}
static void bfq_init_root_group(struct bfq_group *root_group,
struct bfq_data *bfqd)
{
int i;
#ifdef CONFIG_BFQ_GROUP_IOSCHED
root_group->entity.parent = NULL;
root_group->my_entity = NULL;
root_group->bfqd = bfqd;
#endif
root_group->rq_pos_tree = RB_ROOT;
for (i = 0; i < BFQ_IOPRIO_CLASSES; i++)
root_group->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT;
root_group->sched_data.bfq_class_idle_last_service = jiffies;
}
static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
{
struct bfq_data *bfqd;
struct elevator_queue *eq;
eq = elevator_alloc(q, e);
if (!eq)
return -ENOMEM;
bfqd = kzalloc_node(sizeof(*bfqd), GFP_KERNEL, q->node);
if (!bfqd) {
kobject_put(&eq->kobj);
return -ENOMEM;
}
eq->elevator_data = bfqd;
spin_lock_irq(q->queue_lock);
q->elevator = eq;
spin_unlock_irq(q->queue_lock);
/*
* Our fallback bfqq if bfq_find_alloc_queue() runs into OOM issues.
* Grab a permanent reference to it, so that the normal code flow
* will not attempt to free it.
*/
bfq_init_bfqq(bfqd, &bfqd->oom_bfqq, NULL, 1, 0);
bfqd->oom_bfqq.ref++;
bfqd->oom_bfqq.new_ioprio = BFQ_DEFAULT_QUEUE_IOPRIO;
bfqd->oom_bfqq.new_ioprio_class = IOPRIO_CLASS_BE;
bfqd->oom_bfqq.entity.new_weight =
bfq_ioprio_to_weight(bfqd->oom_bfqq.new_ioprio);
/* oom_bfqq does not participate to bursts */
bfq_clear_bfqq_just_created(&bfqd->oom_bfqq);
/*
* Trigger weight initialization, according to ioprio, at the
* oom_bfqq's first activation. The oom_bfqq's ioprio and ioprio
* class won't be changed any more.
*/
bfqd->oom_bfqq.entity.prio_changed = 1;
bfqd->queue = q;
INIT_LIST_HEAD(&bfqd->dispatch);
hrtimer_init(&bfqd->idle_slice_timer, CLOCK_MONOTONIC,
HRTIMER_MODE_REL);
bfqd->idle_slice_timer.function = bfq_idle_slice_timer;
bfqd->queue_weights_tree = RB_ROOT;
bfqd->group_weights_tree = RB_ROOT;
INIT_LIST_HEAD(&bfqd->active_list);
INIT_LIST_HEAD(&bfqd->idle_list);
INIT_HLIST_HEAD(&bfqd->burst_list);
bfqd->hw_tag = -1;
bfqd->bfq_max_budget = bfq_default_max_budget;
bfqd->bfq_fifo_expire[0] = bfq_fifo_expire[0];
bfqd->bfq_fifo_expire[1] = bfq_fifo_expire[1];
bfqd->bfq_back_max = bfq_back_max;
bfqd->bfq_back_penalty = bfq_back_penalty;
bfqd->bfq_slice_idle = bfq_slice_idle;
bfqd->bfq_timeout = bfq_timeout;
bfqd->bfq_requests_within_timer = 120;
bfqd->bfq_large_burst_thresh = 8;
bfqd->bfq_burst_interval = msecs_to_jiffies(180);
bfqd->low_latency = true;
/*
* Trade-off between responsiveness and fairness.
*/
bfqd->bfq_wr_coeff = 30;
bfqd->bfq_wr_rt_max_time = msecs_to_jiffies(300);
bfqd->bfq_wr_max_time = 0;
bfqd->bfq_wr_min_idle_time = msecs_to_jiffies(2000);
bfqd->bfq_wr_min_inter_arr_async = msecs_to_jiffies(500);
bfqd->bfq_wr_max_softrt_rate = 7000; /*
* Approximate rate required
* to playback or record a
* high-definition compressed
* video.
*/
bfqd->wr_busy_queues = 0;
/*
* Begin by assuming, optimistically, that the device is a
* high-speed one, and that its peak rate is equal to 2/3 of
* the highest reference rate.
*/
bfqd->RT_prod = R_fast[blk_queue_nonrot(bfqd->queue)] *
T_fast[blk_queue_nonrot(bfqd->queue)];
bfqd->peak_rate = R_fast[blk_queue_nonrot(bfqd->queue)] * 2 / 3;
bfqd->device_speed = BFQ_BFQD_FAST;
spin_lock_init(&bfqd->lock);
/*
* The invocation of the next bfq_create_group_hierarchy
* function is the head of a chain of function calls
* (bfq_create_group_hierarchy->blkcg_activate_policy->
* blk_mq_freeze_queue) that may lead to the invocation of the
* has_work hook function. For this reason,
* bfq_create_group_hierarchy is invoked only after all
* scheduler data has been initialized, apart from the fields
* that can be initialized only after invoking
* bfq_create_group_hierarchy. This, in particular, enables
* has_work to correctly return false. Of course, to avoid
* other inconsistencies, the blk-mq stack must then refrain
* from invoking further scheduler hooks before this init
* function is finished.
*/
bfqd->root_group = bfq_create_group_hierarchy(bfqd, q->node);
if (!bfqd->root_group)
goto out_free;
bfq_init_root_group(bfqd->root_group, bfqd);
bfq_init_entity(&bfqd->oom_bfqq.entity, bfqd->root_group);
return 0;
out_free:
kfree(bfqd);
kobject_put(&eq->kobj);
return -ENOMEM;
}
static void bfq_slab_kill(void)
{
kmem_cache_destroy(bfq_pool);
}
static int __init bfq_slab_setup(void)
{
bfq_pool = KMEM_CACHE(bfq_queue, 0);
if (!bfq_pool)
return -ENOMEM;
return 0;
}
static ssize_t bfq_var_show(unsigned int var, char *page)
{
return sprintf(page, "%u\n", var);
}
static ssize_t bfq_var_store(unsigned long *var, const char *page,
size_t count)
{
unsigned long new_val;
int ret = kstrtoul(page, 10, &new_val);
if (ret == 0)
*var = new_val;
return count;
}
#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
static ssize_t __FUNC(struct elevator_queue *e, char *page) \
{ \
struct bfq_data *bfqd = e->elevator_data; \
u64 __data = __VAR; \
if (__CONV == 1) \
__data = jiffies_to_msecs(__data); \
else if (__CONV == 2) \
__data = div_u64(__data, NSEC_PER_MSEC); \
return bfq_var_show(__data, (page)); \
}
SHOW_FUNCTION(bfq_fifo_expire_sync_show, bfqd->bfq_fifo_expire[1], 2);
SHOW_FUNCTION(bfq_fifo_expire_async_show, bfqd->bfq_fifo_expire[0], 2);
SHOW_FUNCTION(bfq_back_seek_max_show, bfqd->bfq_back_max, 0);
SHOW_FUNCTION(bfq_back_seek_penalty_show, bfqd->bfq_back_penalty, 0);
SHOW_FUNCTION(bfq_slice_idle_show, bfqd->bfq_slice_idle, 2);
SHOW_FUNCTION(bfq_max_budget_show, bfqd->bfq_user_max_budget, 0);
SHOW_FUNCTION(bfq_timeout_sync_show, bfqd->bfq_timeout, 1);
SHOW_FUNCTION(bfq_strict_guarantees_show, bfqd->strict_guarantees, 0);
SHOW_FUNCTION(bfq_low_latency_show, bfqd->low_latency, 0);
#undef SHOW_FUNCTION
#define USEC_SHOW_FUNCTION(__FUNC, __VAR) \
static ssize_t __FUNC(struct elevator_queue *e, char *page) \
{ \
struct bfq_data *bfqd = e->elevator_data; \
u64 __data = __VAR; \
__data = div_u64(__data, NSEC_PER_USEC); \
return bfq_var_show(__data, (page)); \
}
USEC_SHOW_FUNCTION(bfq_slice_idle_us_show, bfqd->bfq_slice_idle);
#undef USEC_SHOW_FUNCTION
#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
static ssize_t \
__FUNC(struct elevator_queue *e, const char *page, size_t count) \
{ \
struct bfq_data *bfqd = e->elevator_data; \
unsigned long uninitialized_var(__data); \
int ret = bfq_var_store(&__data, (page), count); \
if (__data < (MIN)) \
__data = (MIN); \
else if (__data > (MAX)) \
__data = (MAX); \
if (__CONV == 1) \
*(__PTR) = msecs_to_jiffies(__data); \
else if (__CONV == 2) \
*(__PTR) = (u64)__data * NSEC_PER_MSEC; \
else \
*(__PTR) = __data; \
return ret; \
}
STORE_FUNCTION(bfq_fifo_expire_sync_store, &bfqd->bfq_fifo_expire[1], 1,
INT_MAX, 2);
STORE_FUNCTION(bfq_fifo_expire_async_store, &bfqd->bfq_fifo_expire[0], 1,
INT_MAX, 2);
STORE_FUNCTION(bfq_back_seek_max_store, &bfqd->bfq_back_max, 0, INT_MAX, 0);
STORE_FUNCTION(bfq_back_seek_penalty_store, &bfqd->bfq_back_penalty, 1,
INT_MAX, 0);
STORE_FUNCTION(bfq_slice_idle_store, &bfqd->bfq_slice_idle, 0, INT_MAX, 2);
#undef STORE_FUNCTION
#define USEC_STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \
static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)\
{ \
struct bfq_data *bfqd = e->elevator_data; \
unsigned long uninitialized_var(__data); \
int ret = bfq_var_store(&__data, (page), count); \
if (__data < (MIN)) \
__data = (MIN); \
else if (__data > (MAX)) \
__data = (MAX); \
*(__PTR) = (u64)__data * NSEC_PER_USEC; \
return ret; \
}
USEC_STORE_FUNCTION(bfq_slice_idle_us_store, &bfqd->bfq_slice_idle, 0,
UINT_MAX);
#undef USEC_STORE_FUNCTION
static ssize_t bfq_max_budget_store(struct elevator_queue *e,
const char *page, size_t count)
{
struct bfq_data *bfqd = e->elevator_data;
unsigned long uninitialized_var(__data);
int ret = bfq_var_store(&__data, (page), count);
if (__data == 0)
bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd);
else {
if (__data > INT_MAX)
__data = INT_MAX;
bfqd->bfq_max_budget = __data;
}
bfqd->bfq_user_max_budget = __data;
return ret;
}
/*
* Leaving this name to preserve name compatibility with cfq
* parameters, but this timeout is used for both sync and async.
*/
static ssize_t bfq_timeout_sync_store(struct elevator_queue *e,
const char *page, size_t count)
{
struct bfq_data *bfqd = e->elevator_data;
unsigned long uninitialized_var(__data);
int ret = bfq_var_store(&__data, (page), count);
if (__data < 1)
__data = 1;
else if (__data > INT_MAX)
__data = INT_MAX;
bfqd->bfq_timeout = msecs_to_jiffies(__data);
if (bfqd->bfq_user_max_budget == 0)
bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd);
return ret;
}
static ssize_t bfq_strict_guarantees_store(struct elevator_queue *e,
const char *page, size_t count)
{
struct bfq_data *bfqd = e->elevator_data;
unsigned long uninitialized_var(__data);
int ret = bfq_var_store(&__data, (page), count);
if (__data > 1)
__data = 1;
if (!bfqd->strict_guarantees && __data == 1
&& bfqd->bfq_slice_idle < 8 * NSEC_PER_MSEC)
bfqd->bfq_slice_idle = 8 * NSEC_PER_MSEC;
bfqd->strict_guarantees = __data;
return ret;
}
static ssize_t bfq_low_latency_store(struct elevator_queue *e,
const char *page, size_t count)
{
struct bfq_data *bfqd = e->elevator_data;
unsigned long uninitialized_var(__data);
int ret = bfq_var_store(&__data, (page), count);
if (__data > 1)
__data = 1;
if (__data == 0 && bfqd->low_latency != 0)
bfq_end_wr(bfqd);
bfqd->low_latency = __data;
return ret;
}
#define BFQ_ATTR(name) \
__ATTR(name, 0644, bfq_##name##_show, bfq_##name##_store)
static struct elv_fs_entry bfq_attrs[] = {
BFQ_ATTR(fifo_expire_sync),
BFQ_ATTR(fifo_expire_async),
BFQ_ATTR(back_seek_max),
BFQ_ATTR(back_seek_penalty),
BFQ_ATTR(slice_idle),
BFQ_ATTR(slice_idle_us),
BFQ_ATTR(max_budget),
BFQ_ATTR(timeout_sync),
BFQ_ATTR(strict_guarantees),
BFQ_ATTR(low_latency),
__ATTR_NULL
};
static struct elevator_type iosched_bfq_mq = {
.ops.mq = {
.get_rq_priv = bfq_get_rq_private,
.put_rq_priv = bfq_put_rq_private,
.exit_icq = bfq_exit_icq,
.insert_requests = bfq_insert_requests,
.dispatch_request = bfq_dispatch_request,
.next_request = elv_rb_latter_request,
.former_request = elv_rb_former_request,
.allow_merge = bfq_allow_bio_merge,
.bio_merge = bfq_bio_merge,
.request_merge = bfq_request_merge,
.requests_merged = bfq_requests_merged,
.request_merged = bfq_request_merged,
.has_work = bfq_has_work,
.init_sched = bfq_init_queue,
.exit_sched = bfq_exit_queue,
},
.uses_mq = true,
.icq_size = sizeof(struct bfq_io_cq),
.icq_align = __alignof__(struct bfq_io_cq),
.elevator_attrs = bfq_attrs,
.elevator_name = "bfq",
.elevator_owner = THIS_MODULE,
};
#ifdef CONFIG_BFQ_GROUP_IOSCHED
static struct blkcg_policy blkcg_policy_bfq = {
.dfl_cftypes = bfq_blkg_files,
.legacy_cftypes = bfq_blkcg_legacy_files,
.cpd_alloc_fn = bfq_cpd_alloc,
.cpd_init_fn = bfq_cpd_init,
.cpd_bind_fn = bfq_cpd_init,
.cpd_free_fn = bfq_cpd_free,
.pd_alloc_fn = bfq_pd_alloc,
.pd_init_fn = bfq_pd_init,
.pd_offline_fn = bfq_pd_offline,
.pd_free_fn = bfq_pd_free,
.pd_reset_stats_fn = bfq_pd_reset_stats,
};
#endif
static int __init bfq_init(void)
{
int ret;
#ifdef CONFIG_BFQ_GROUP_IOSCHED
ret = blkcg_policy_register(&blkcg_policy_bfq);
if (ret)
return ret;
#endif
ret = -ENOMEM;
if (bfq_slab_setup())
goto err_pol_unreg;
/*
* Times to load large popular applications for the typical
* systems installed on the reference devices (see the
* comments before the definitions of the next two
* arrays). Actually, we use slightly slower values, as the
* estimated peak rate tends to be smaller than the actual
* peak rate. The reason for this last fact is that estimates
* are computed over much shorter time intervals than the long
* intervals typically used for benchmarking. Why? First, to
* adapt more quickly to variations. Second, because an I/O
* scheduler cannot rely on a peak-rate-evaluation workload to
* be run for a long time.
*/
T_slow[0] = msecs_to_jiffies(3500); /* actually 4 sec */
T_slow[1] = msecs_to_jiffies(6000); /* actually 6.5 sec */
T_fast[0] = msecs_to_jiffies(7000); /* actually 8 sec */
T_fast[1] = msecs_to_jiffies(2500); /* actually 3 sec */
/*
* Thresholds that determine the switch between speed classes
* (see the comments before the definition of the array
* device_speed_thresh). These thresholds are biased towards
* transitions to the fast class. This is safer than the
* opposite bias. In fact, a wrong transition to the slow
* class results in short weight-raising periods, because the
* speed of the device then tends to be higher that the
* reference peak rate. On the opposite end, a wrong
* transition to the fast class tends to increase
* weight-raising periods, because of the opposite reason.
*/
device_speed_thresh[0] = (4 * R_slow[0]) / 3;
device_speed_thresh[1] = (4 * R_slow[1]) / 3;
ret = elv_register(&iosched_bfq_mq);
if (ret)
goto err_pol_unreg;
return 0;
err_pol_unreg:
#ifdef CONFIG_BFQ_GROUP_IOSCHED
blkcg_policy_unregister(&blkcg_policy_bfq);
#endif
return ret;
}
static void __exit bfq_exit(void)
{
elv_unregister(&iosched_bfq_mq);
#ifdef CONFIG_BFQ_GROUP_IOSCHED
blkcg_policy_unregister(&blkcg_policy_bfq);
#endif
bfq_slab_kill();
}
module_init(bfq_init);
module_exit(bfq_exit);
MODULE_AUTHOR("Paolo Valente");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("MQ Budget Fair Queueing I/O Scheduler");
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