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mm: memcg: only check swap cache pages for repeated charging

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Only anon and shmem pages in the swap cache are attempted to be charged
multiple times, from every swap pte fault or from shmem_unuse().  No other
pages require checking PageCgroupUsed().

Charging pages in the swap cache is also serialized by the page lock, and
since both the try_charge and commit_charge are called under the same page
lock section, the PageCgroupUsed() check might as well happen before the
counter charging, let alone reclaim.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Wanpeng Li <liwp.linux@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2012-07-31 16:45:47 -07:00 committed by Linus Torvalds
parent 0435a2fdcb
commit 90deb78839
1 changed files with 12 additions and 5 deletions
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17
mm/memcontrol.c
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@ -2538,11 +2538,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
bool anon;
lock_page_cgroup(pc);
if (unlikely(PageCgroupUsed(pc))) {
unlock_page_cgroup(pc);
__mem_cgroup_cancel_charge(memcg, nr_pages);
return;
}
VM_BUG_ON(PageCgroupUsed(pc));
/*
* we don't need page_cgroup_lock about tail pages, becase they are not
* accessed by any other context at this point.
@ -2807,8 +2803,19 @@ static int __mem_cgroup_try_charge_swapin(struct mm_struct *mm,
struct mem_cgroup **memcgp)
{
struct mem_cgroup *memcg;
struct page_cgroup *pc;
int ret;
pc = lookup_page_cgroup(page);
/*
* Every swap fault against a single page tries to charge the
* page, bail as early as possible. shmem_unuse() encounters
* already charged pages, too. The USED bit is protected by
* the page lock, which serializes swap cache removal, which
* in turn serializes uncharging.
*/
if (PageCgroupUsed(pc))
return 0;
if (!do_swap_account)
goto charge_cur_mm;
/*