Commit 90deb788 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds

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

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: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: default avatarMichal 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0435a2fd
...@@ -2538,11 +2538,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg, ...@@ -2538,11 +2538,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
bool anon; bool anon;
lock_page_cgroup(pc); lock_page_cgroup(pc);
if (unlikely(PageCgroupUsed(pc))) { VM_BUG_ON(PageCgroupUsed(pc));
unlock_page_cgroup(pc);
__mem_cgroup_cancel_charge(memcg, nr_pages);
return;
}
/* /*
* we don't need page_cgroup_lock about tail pages, becase they are not * we don't need page_cgroup_lock about tail pages, becase they are not
* accessed by any other context at this point. * accessed by any other context at this point.
...@@ -2807,8 +2803,19 @@ static int __mem_cgroup_try_charge_swapin(struct mm_struct *mm, ...@@ -2807,8 +2803,19 @@ static int __mem_cgroup_try_charge_swapin(struct mm_struct *mm,
struct mem_cgroup **memcgp) struct mem_cgroup **memcgp)
{ {
struct mem_cgroup *memcg; struct mem_cgroup *memcg;
struct page_cgroup *pc;
int ret; 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) if (!do_swap_account)
goto charge_cur_mm; goto charge_cur_mm;
/* /*
......
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