memcg: remove PCG_MOVE_LOCK flag from page_cgroup
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>
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Linus Torvalds

parent
619d094b58
commit
312734c04e
@@ -7,7 +7,6 @@ enum {
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PCG_USED, /* this object is in use. */
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PCG_MIGRATION, /* under page migration */
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/* flags for mem_cgroup and file and I/O status */
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PCG_MOVE_LOCK, /* For race between move_account v.s. following bits */
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PCG_FILE_MAPPED, /* page is accounted as "mapped" */
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__NR_PCG_FLAGS,
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};
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@@ -89,24 +88,6 @@ static inline void unlock_page_cgroup(struct page_cgroup *pc)
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bit_spin_unlock(PCG_LOCK, &pc->flags);
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}
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static inline void move_lock_page_cgroup(struct page_cgroup *pc,
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unsigned long *flags)
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{
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/*
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* We know updates to pc->flags of page cache's stats are from both of
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* usual context or IRQ context. Disable IRQ to avoid deadlock.
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*/
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local_irq_save(*flags);
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bit_spin_lock(PCG_MOVE_LOCK, &pc->flags);
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}
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static inline void move_unlock_page_cgroup(struct page_cgroup *pc,
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unsigned long *flags)
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{
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bit_spin_unlock(PCG_MOVE_LOCK, &pc->flags);
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local_irq_restore(*flags);
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}
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#else /* CONFIG_CGROUP_MEM_RES_CTLR */
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struct page_cgroup;
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