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authorJohannes Weiner <hannes@cmpxchg.org>2014-08-06 16:06:04 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-08-06 18:01:17 -0700
commita840cda63e543d41270698525542a82b7a8a18d7 (patch)
tree4e16e7a67514e3e3cbcd9368fdfeab8fd76f01f2 /mm
parent9a2385eef9f28fb5260c48c45fc8fe01f1da70a6 (diff)
downloadlinux-a840cda63e543d41270698525542a82b7a8a18d7.tar.gz
mm: memcontrol: do not acquire page_cgroup lock for kmem pages
Kmem page charging and uncharging is serialized by means of exclusive access to the page. Do not take the page_cgroup lock and don't set pc->flags atomically. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Vladimir Davydov <vdavydov@parallels.com> Cc: Hugh Dickins <hughd@google.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memcontrol.c21
1 files changed, 7 insertions, 14 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c31bc40a5827..a6a062e409eb 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3407,12 +3407,13 @@ void __memcg_kmem_commit_charge(struct page *page, struct mem_cgroup *memcg,
memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
return;
}
-
+ /*
+ * The page is freshly allocated and not visible to any
+ * outside callers yet. Set up pc non-atomically.
+ */
pc = lookup_page_cgroup(page);
- lock_page_cgroup(pc);
pc->mem_cgroup = memcg;
- SetPageCgroupUsed(pc);
- unlock_page_cgroup(pc);
+ pc->flags = PCG_USED;
}
void __memcg_kmem_uncharge_pages(struct page *page, int order)
@@ -3422,19 +3423,11 @@ void __memcg_kmem_uncharge_pages(struct page *page, int order)
pc = lookup_page_cgroup(page);
- /*
- * Fast unlocked return. Theoretically might have changed, have to
- * check again after locking.
- */
if (!PageCgroupUsed(pc))
return;
- lock_page_cgroup(pc);
- if (PageCgroupUsed(pc)) {
- memcg = pc->mem_cgroup;
- ClearPageCgroupUsed(pc);
- }
- unlock_page_cgroup(pc);
+ memcg = pc->mem_cgroup;
+ pc->flags = 0;
/*
* We trust that only if there is a memcg associated with the page, it