Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 4e701d7b authored by Vladimir Davydov's avatar Vladimir Davydov Committed by Linus Torvalds
Browse files

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: default avatarVladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 900a38f0

mm/memcontrol.c

+0 −28
Original line number Diff line number Diff line
@@ -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)) {