![Qu Wenruo](/assets/img/avatar_default.png)
The original btrfs_workers has thresholding functions to dynamically create or destroy kthreads. Though there is no such function in kernel workqueue because the worker is not created manually, we can still use the workqueue_set_max_active to simulated the behavior, mainly to achieve a better HDD performance by setting a high threshold on submit_workers. (Sadly, no resource can be saved) So in this patch, extra workqueue pending counters are introduced to dynamically change the max active of each btrfs_workqueue_struct, hoping to restore the behavior of the original thresholding function. Also, workqueue_set_max_active use a mutex to protect workqueue_struct, which is not meant to be called too frequently, so a new interval mechanism is applied, that will only call workqueue_set_max_active after a count of work is queued. Hoping to balance both the random and sequence performance on HDD. Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com> Tested-by: David Sterba <dsterba@suse.cz> Signed-off-by: Josef Bacik <jbacik@fb.com>
153 lines
4.9 KiB
C
153 lines
4.9 KiB
C
/*
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* Copyright (C) 2007 Oracle. All rights reserved.
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* Copyright (C) 2014 Fujitsu. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*/
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#ifndef __BTRFS_ASYNC_THREAD_
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#define __BTRFS_ASYNC_THREAD_
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struct btrfs_worker_thread;
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/*
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* This is similar to a workqueue, but it is meant to spread the operations
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* across all available cpus instead of just the CPU that was used to
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* queue the work. There is also some batching introduced to try and
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* cut down on context switches.
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*
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* By default threads are added on demand up to 2 * the number of cpus.
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* Changing struct btrfs_workers->max_workers is one way to prevent
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* demand creation of kthreads.
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*
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* the basic model of these worker threads is to embed a btrfs_work
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* structure in your own data struct, and use container_of in a
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* work function to get back to your data struct.
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*/
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struct btrfs_work {
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/*
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* func should be set to the function you want called
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* your work struct is passed as the only arg
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*
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* ordered_func must be set for work sent to an ordered work queue,
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* and it is called to complete a given work item in the same
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* order they were sent to the queue.
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*/
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void (*func)(struct btrfs_work *work);
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void (*ordered_func)(struct btrfs_work *work);
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void (*ordered_free)(struct btrfs_work *work);
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/*
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* flags should be set to zero. It is used to make sure the
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* struct is only inserted once into the list.
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*/
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unsigned long flags;
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/* don't touch these */
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struct btrfs_worker_thread *worker;
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struct list_head list;
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struct list_head order_list;
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};
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struct btrfs_workers {
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/* current number of running workers */
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int num_workers;
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int num_workers_starting;
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/* max number of workers allowed. changed by btrfs_start_workers */
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int max_workers;
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/* once a worker has this many requests or fewer, it is idle */
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int idle_thresh;
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/* force completions in the order they were queued */
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int ordered;
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/* more workers required, but in an interrupt handler */
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int atomic_start_pending;
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/*
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* are we allowed to sleep while starting workers or are we required
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* to start them at a later time? If we can't sleep, this indicates
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* which queue we need to use to schedule thread creation.
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*/
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struct btrfs_workers *atomic_worker_start;
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/* list with all the work threads. The workers on the idle thread
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* may be actively servicing jobs, but they haven't yet hit the
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* idle thresh limit above.
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*/
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struct list_head worker_list;
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struct list_head idle_list;
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/*
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* when operating in ordered mode, this maintains the list
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* of work items waiting for completion
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*/
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struct list_head order_list;
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struct list_head prio_order_list;
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/* lock for finding the next worker thread to queue on */
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spinlock_t lock;
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/* lock for the ordered lists */
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spinlock_t order_lock;
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/* extra name for this worker, used for current->name */
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char *name;
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int stopping;
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};
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void btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work);
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int btrfs_start_workers(struct btrfs_workers *workers);
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void btrfs_stop_workers(struct btrfs_workers *workers);
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void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max,
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struct btrfs_workers *async_starter);
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void btrfs_requeue_work(struct btrfs_work *work);
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void btrfs_set_work_high_prio(struct btrfs_work *work);
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struct btrfs_workqueue_struct;
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/* Internal use only */
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struct __btrfs_workqueue_struct;
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struct btrfs_work_struct {
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void (*func)(struct btrfs_work_struct *arg);
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void (*ordered_func)(struct btrfs_work_struct *arg);
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void (*ordered_free)(struct btrfs_work_struct *arg);
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/* Don't touch things below */
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struct work_struct normal_work;
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struct list_head ordered_list;
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struct __btrfs_workqueue_struct *wq;
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unsigned long flags;
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};
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struct btrfs_workqueue_struct *btrfs_alloc_workqueue(char *name,
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int flags,
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int max_active,
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int thresh);
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void btrfs_init_work(struct btrfs_work_struct *work,
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void (*func)(struct btrfs_work_struct *),
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void (*ordered_func)(struct btrfs_work_struct *),
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void (*ordered_free)(struct btrfs_work_struct *));
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void btrfs_queue_work(struct btrfs_workqueue_struct *wq,
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struct btrfs_work_struct *work);
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void btrfs_destroy_workqueue(struct btrfs_workqueue_struct *wq);
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void btrfs_workqueue_set_max(struct btrfs_workqueue_struct *wq, int max);
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void btrfs_set_work_high_priority(struct btrfs_work_struct *work);
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#endif
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