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memcg: remove PCG_MOVE_LOCK flag from page_cgroup

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PCG_MOVE_LOCK is used for bit spinlock to avoid race between overwriting
pc->mem_cgroup and page statistics accounting per memcg.  This lock helps
to avoid the race but the race is very rare because moving tasks between
cgroup is not a usual job.  So, it seems using 1bit per page is too
costly.

This patch changes this lock as per-memcg spinlock and removes
PCG_MOVE_LOCK.

If smaller lock is required, we'll be able to add some hashes but I'd like
to start from this.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Greg Thelen <gthelen@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KAMEZAWA Hiroyuki 2012-03-21 16:34:24 -07:00 • committed by Linus Torvalds
commit 312734c04e
2 changed files with 32 additions and 29 deletions
Download patch file Download diff file Expand all files Collapse all files

19
include/linux/page_cgroup.h
View file

@ -7,7 +7,6 @@ enum {
PCG_USED, /* this object is in use. */
PCG_MIGRATION, /* under page migration */
/* flags for mem_cgroup and file and I/O status */
PCG_MOVE_LOCK, /* For race between move_account v.s. following bits */
PCG_FILE_MAPPED, /* page is accounted as "mapped" */
__NR_PCG_FLAGS,
};
@ -89,24 +88,6 @@ static inline void unlock_page_cgroup(struct page_cgroup *pc)
bit_spin_unlock(PCG_LOCK, &pc->flags);
}
static inline void move_lock_page_cgroup(struct page_cgroup *pc,
unsigned long *flags)
{
/*
* We know updates to pc->flags of page cache's stats are from both of
* usual context or IRQ context. Disable IRQ to avoid deadlock.
*/
local_irq_save(*flags);
bit_spin_lock(PCG_MOVE_LOCK, &pc->flags);
}
static inline void move_unlock_page_cgroup(struct page_cgroup *pc,
unsigned long *flags)
{
bit_spin_unlock(PCG_MOVE_LOCK, &pc->flags);
local_irq_restore(*flags);
}
#else /* CONFIG_CGROUP_MEM_RES_CTLR */
struct page_cgroup;