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author | Vladimir Davydov <vdavydov@virtuozzo.com> | 2016-03-17 22:17:29 +0100 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-03-17 23:09:34 +0100 |
commit | fcff7d7eebe6d31e2ce20d994555c86a90197034 (patch) | |
tree | 776a49bee21274e04baf973a281fb764df4764b1 /mm | |
parent | mm: oom_kill: don't ignore oom score on exiting tasks (diff) | |
download | linux-fcff7d7eebe6d31e2ce20d994555c86a90197034.tar.xz linux-fcff7d7eebe6d31e2ce20d994555c86a90197034.zip |
mm: memcontrol: do not bypass slab charge if memcg is offline
Slab pages are charged in two steps. First, an appropriate per memcg
cache is selected (see memcg_kmem_get_cache) basing on the current
context, then the new slab page is charged to the memory cgroup which
the selected cache was created for (see memcg_charge_slab ->
__memcg_kmem_charge_memcg). It is OK to bypass kmemcg charge at step 1,
but if step 1 succeeded and we successfully allocated a new slab page,
step 2 must be performed, otherwise we would get a per memcg kmem cache
which contains a slab that does not hold a reference to the memory
cgroup owning the cache. Since per memcg kmem caches are destroyed on
memcg css free, this could result in freeing a cache while there are
still active objects in it.
However, currently we will bypass slab page charge if the memory cgroup
owning the cache is offline (see __memcg_kmem_charge_memcg). This is
very unlikely to occur in practice, because for this to happen a process
must be migrated to a different cgroup and the old cgroup must be
removed while the process is in kmalloc somewhere between steps 1 and 2
(e.g. trying to allocate a new page). Nevertheless, it's still better
to eliminate such a possibility.
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@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 | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 42882c1e7fce..5c9d45e4c739 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2325,9 +2325,6 @@ int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order, struct page_counter *counter; int ret; - if (!memcg_kmem_online(memcg)) - return 0; - ret = try_charge(memcg, gfp, nr_pages); if (ret) return ret; @@ -2346,10 +2343,11 @@ int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order, int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order) { struct mem_cgroup *memcg; - int ret; + int ret = 0; memcg = get_mem_cgroup_from_mm(current->mm); - ret = __memcg_kmem_charge_memcg(page, gfp, order, memcg); + if (memcg_kmem_online(memcg)) + ret = __memcg_kmem_charge_memcg(page, gfp, order, memcg); css_put(&memcg->css); return ret; } |