2027d1abc2
After scalability problems have been detected when using the sysV ipcs, I have
proposed to use an RCU based implementation of the IDR api instead (see
threads http://lkml.org/lkml/2008/4/11/212 and
http://lkml.org/lkml/2008/4/29/295).
This resulted in many people asking to convert the idr API and make it rcu
safe (because most of the code was duplicated and thus unmaintanable and
unreviewable).
So here is a first attempt.
The important change wrt to the idr API itself is during idr removes: idr
layers are freed after a grace period, instead of being moved to the free
list.
The important change wrt to ipcs, is that idr_find() can now be called
locklessly inside a rcu read critical section.
Here are the results I've got for the pmsg test sent by Manfred:
2.6.25-rc3-mm1 2.6.25-rc3-mm1+ 2.6.25-mm1 Patched 2.6.25-mm1
1 1168441 1064021 876000 947488
2 1094264 921059 1549592 1730685
3 2082520 1738165 1694370 2324880
4 2079929 1695521 404553 2400408
5 2898758 406566 391283 3246580
6 2921417 261275 263249 3752148
7 3308761 126056 191742 4243142
8 3329456 100129 141722 4275780
1st column: stock 2.6.25-rc3-mm1
2nd column: 2.6.25-rc3-mm1 + ipc patches (store ipcs into idrs)
3nd column: stock 2.6.25-mm1
4th column: 2.6.25-mm1 + this pacth series.
This patch:
Add an rcu_head to the idr_layer structure in order to free it after a grace
period.
Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
Reviewed-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Jim Houston <jim.houston@comcast.net>
Cc: Pierre Peiffer <peifferp@gmail.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
124 lines
3.4 KiB
C
124 lines
3.4 KiB
C
/*
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* include/linux/idr.h
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*
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* 2002-10-18 written by Jim Houston jim.houston@ccur.com
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* Copyright (C) 2002 by Concurrent Computer Corporation
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* Distributed under the GNU GPL license version 2.
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*
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* Small id to pointer translation service avoiding fixed sized
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* tables.
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*/
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#ifndef __IDR_H__
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#define __IDR_H__
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#include <linux/types.h>
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#include <linux/bitops.h>
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#include <linux/init.h>
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#include <linux/rcupdate.h>
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#if BITS_PER_LONG == 32
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# define IDR_BITS 5
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# define IDR_FULL 0xfffffffful
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/* We can only use two of the bits in the top level because there is
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only one possible bit in the top level (5 bits * 7 levels = 35
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bits, but you only use 31 bits in the id). */
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# define TOP_LEVEL_FULL (IDR_FULL >> 30)
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#elif BITS_PER_LONG == 64
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# define IDR_BITS 6
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# define IDR_FULL 0xfffffffffffffffful
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/* We can only use two of the bits in the top level because there is
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only one possible bit in the top level (6 bits * 6 levels = 36
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bits, but you only use 31 bits in the id). */
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# define TOP_LEVEL_FULL (IDR_FULL >> 62)
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#else
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# error "BITS_PER_LONG is not 32 or 64"
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#endif
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#define IDR_SIZE (1 << IDR_BITS)
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#define IDR_MASK ((1 << IDR_BITS)-1)
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#define MAX_ID_SHIFT (sizeof(int)*8 - 1)
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#define MAX_ID_BIT (1U << MAX_ID_SHIFT)
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#define MAX_ID_MASK (MAX_ID_BIT - 1)
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/* Leave the possibility of an incomplete final layer */
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#define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS
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/* Number of id_layer structs to leave in free list */
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#define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL
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struct idr_layer {
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unsigned long bitmap; /* A zero bit means "space here" */
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struct idr_layer *ary[1<<IDR_BITS];
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int count; /* When zero, we can release it */
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struct rcu_head rcu_head;
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};
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struct idr {
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struct idr_layer *top;
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struct idr_layer *id_free;
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int layers;
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int id_free_cnt;
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spinlock_t lock;
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};
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#define IDR_INIT(name) \
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{ \
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.top = NULL, \
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.id_free = NULL, \
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.layers = 0, \
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.id_free_cnt = 0, \
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.lock = __SPIN_LOCK_UNLOCKED(name.lock), \
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}
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#define DEFINE_IDR(name) struct idr name = IDR_INIT(name)
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/*
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* This is what we export.
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*/
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void *idr_find(struct idr *idp, int id);
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int idr_pre_get(struct idr *idp, gfp_t gfp_mask);
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int idr_get_new(struct idr *idp, void *ptr, int *id);
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int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
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int idr_for_each(struct idr *idp,
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int (*fn)(int id, void *p, void *data), void *data);
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void *idr_replace(struct idr *idp, void *ptr, int id);
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void idr_remove(struct idr *idp, int id);
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void idr_remove_all(struct idr *idp);
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void idr_destroy(struct idr *idp);
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void idr_init(struct idr *idp);
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/*
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* IDA - IDR based id allocator, use when translation from id to
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* pointer isn't necessary.
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*/
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#define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */
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#define IDA_BITMAP_LONGS (128 / sizeof(long) - 1)
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#define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8)
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struct ida_bitmap {
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long nr_busy;
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unsigned long bitmap[IDA_BITMAP_LONGS];
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};
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struct ida {
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struct idr idr;
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struct ida_bitmap *free_bitmap;
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};
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#define IDA_INIT(name) { .idr = IDR_INIT(name), .free_bitmap = NULL, }
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#define DEFINE_IDA(name) struct ida name = IDA_INIT(name)
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int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
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int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
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int ida_get_new(struct ida *ida, int *p_id);
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void ida_remove(struct ida *ida, int id);
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void ida_destroy(struct ida *ida);
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void ida_init(struct ida *ida);
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void __init idr_init_cache(void);
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#endif /* __IDR_H__ */
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