diff options
| author | Johannes Weiner <hannes@cmpxchg.org> | 2014-08-06 16:06:04 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-08-06 18:01:17 -0700 |
| commit | a840cda63e543d41270698525542a82b7a8a18d7 (patch) | |
| tree | 4e16e7a67514e3e3cbcd9368fdfeab8fd76f01f2 /mm | |
| parent | 9a2385eef9f28fb5260c48c45fc8fe01f1da70a6 (diff) | |
| download | linux-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.c | 21 |
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 |