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Commit 06b078fc authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
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mm: memcontrol: rearrange charging fast path 



The charging path currently starts out with OOM condition checks when
OOM is the rarest possible case.

Rearrange this code to run OOM/task dying checks only after trying the
percpu charge and the res_counter charge and bail out before entering
reclaim.  Attempting a charge does not hurt an (oom-)killed task as much
as every charge attempt having to check OOM conditions.  Also, only
check __GFP_NOFAIL when the charge would actually fail.

Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6539cc05

mm/memcontrol.c

+17 −16
Original line number Diff line number Diff line
@@ -2575,22 +2575,6 @@ static int mem_cgroup_try_charge(struct mem_cgroup *memcg, 


	if (mem_cgroup_is_root(memcg))

		goto done;

	/*

	 * Unlike in global OOM situations, memcg is not in a physical

	 * memory shortage.  Allow dying and OOM-killed tasks to

	 * bypass the last charges so that they can exit quickly and

	 * free their memory.

	 */

	if (unlikely(test_thread_flag(TIF_MEMDIE) ||

		     fatal_signal_pending(current) ||

		     current->flags & PF_EXITING))

		goto bypass;



	if (unlikely(task_in_memcg_oom(current)))

		goto nomem;



	if (gfp_mask & __GFP_NOFAIL)

		oom = false;

retry:

	if (consume_stock(memcg, nr_pages))

		goto done;
@@ -2612,6 +2596,20 @@ static int mem_cgroup_try_charge(struct mem_cgroup *memcg, 
		goto retry;

	}



	/*

	 * Unlike in global OOM situations, memcg is not in a physical

	 * memory shortage.  Allow dying and OOM-killed tasks to

	 * bypass the last charges so that they can exit quickly and

	 * free their memory.

	 */

	if (unlikely(test_thread_flag(TIF_MEMDIE) ||

		     fatal_signal_pending(current) ||

		     current->flags & PF_EXITING))

		goto bypass;



	if (unlikely(task_in_memcg_oom(current)))

		goto nomem;



	if (!(gfp_mask & __GFP_WAIT))

		goto nomem;
@@ -2640,6 +2638,9 @@ static int mem_cgroup_try_charge(struct mem_cgroup *memcg, 
	if (mem_cgroup_wait_acct_move(mem_over_limit))

		goto retry;



	if (gfp_mask & __GFP_NOFAIL)

		goto bypass;



	if (fatal_signal_pending(current))

		goto bypass;