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memcg: only check memcg_kmem_skip_account in __memcg_kmem_get_cache 

__memcg_kmem_get_cache can recurse if it calls kmalloc (which it does if
the cgroup's kmem cache doesn't exist), because kmalloc may call
__memcg_kmem_get_cache internally again.  To avoid the recursion, we use
the task_struct->memcg_kmem_skip_account flag.

However, there's no need checking the flag in memcg_kmem_newpage_charge,
because there's no way how this function could result in recursion, if
called from memcg_kmem_get_cache.  So let's remove the redundant code.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vladimir Davydov 2014-12-12 16:55:13 -08:00 committed by Linus Torvalds
parent 900a38f027
commit 4e701d7b37
1 changed files with 0 additions and 28 deletions
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28
mm/memcontrol.c
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@ -2905,34 +2905,6 @@ __memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **_memcg, int order)
*_memcg = NULL;
/*
* Disabling accounting is only relevant for some specific memcg
* internal allocations. Therefore we would initially not have such
* check here, since direct calls to the page allocator that are
* accounted to kmemcg (alloc_kmem_pages and friends) only happen
* outside memcg core. We are mostly concerned with cache allocations,
* and by having this test at memcg_kmem_get_cache, we are already able
* to relay the allocation to the root cache and bypass the memcg cache
* altogether.
*
* There is one exception, though: the SLUB allocator does not create
* large order caches, but rather service large kmallocs directly from
* the page allocator. Therefore, the following sequence when backed by
* the SLUB allocator:
*
* memcg_stop_kmem_account();
* kmalloc(<large_number>)
* memcg_resume_kmem_account();
*
* would effectively ignore the fact that we should skip accounting,
* since it will drive us directly to this function without passing
* through the cache selector memcg_kmem_get_cache. Such large
* allocations are extremely rare but can happen, for instance, for the
* cache arrays. We bring this test here.
*/
if (current->memcg_kmem_skip_account)
return true;
memcg = get_mem_cgroup_from_mm(current->mm);
if (!memcg_kmem_is_active(memcg)) {