* [PATCH] memcg, oom: check memcg margin for parallel oom
@ 2020-11-06 8:51 zhongjiang-ali
2020-11-09 7:56 ` zhong jiang
0 siblings, 1 reply; 2+ messages in thread
From: zhongjiang-ali @ 2020-11-06 8:51 UTC (permalink / raw)
To: hannes, mhocko, akpm; +Cc: linux-mm
From: Yafang Shao <laoar.shao@gmail.com>
Memcg oom killer invocation is synchronized by the global oom_lock and
tasks are sleeping on the lock while somebody is selecting the victim or
potentially race with the oom_reaper is releasing the victim's memory.
This can result in a pointless oom killer invocation because a waiter
might be racing with the oom_reaper
P1 oom_reaper P2
oom_reap_task mutex_lock(oom_lock)
out_of_memory # no victim because we have one already
__oom_reap_task_mm mute_unlock(oom_lock)
mutex_lock(oom_lock)
set MMF_OOM_SKIP
select_bad_process
# finds a new victim
The page allocator prevents from this race by trying to allocate after the
lock can be acquired (in __alloc_pages_may_oom) which acts as a last
minute check. Moreover page allocator simply doesn't block on the
oom_lock and simply retries the whole reclaim process.
Memcg oom killer should do the last minute check as well. Call
mem_cgroup_margin to do that. Trylock on the oom_lock could be done as
well but this doesn't seem to be necessary at this stage.
[mhocko@kernel.org: commit log]
Suggested-by: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Chris Down <chris@chrisdown.name>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Link: http://lkml.kernel.org/r/1594735034-19190-1-git-send-email-laoar.shao@gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: zhongjiang-ali <zhongjiang-ali@linux.alibaba.com>
---
mm/memcontrol.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b30a52d..369d9e1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1663,15 +1663,21 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
.gfp_mask = gfp_mask,
.order = order,
};
- bool ret;
+ bool ret = true;
if (mutex_lock_killable(&oom_lock))
return true;
+
+ if (mem_cgroup_margin(memcg) >= (1 << order))
+ goto unlock;
+
/*
* A few threads which were not waiting at mutex_lock_killable() can
* fail to bail out. Therefore, check again after holding oom_lock.
*/
ret = should_force_charge() || out_of_memory(&oc);
+
+unlock:
mutex_unlock(&oom_lock);
return ret;
}
--
1.8.3.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] memcg, oom: check memcg margin for parallel oom
2020-11-06 8:51 [PATCH] memcg, oom: check memcg margin for parallel oom zhongjiang-ali
@ 2020-11-09 7:56 ` zhong jiang
0 siblings, 0 replies; 2+ messages in thread
From: zhong jiang @ 2020-11-09 7:56 UTC (permalink / raw)
To: hannes, mhocko, akpm; +Cc: linux-mm
I am sorry for my stupid email. Please ignore it. Thanks😅
On 2020/11/6 4:51 下午, zhongjiang-ali wrote:
> From: Yafang Shao <laoar.shao@gmail.com>
>
> Memcg oom killer invocation is synchronized by the global oom_lock and
> tasks are sleeping on the lock while somebody is selecting the victim or
> potentially race with the oom_reaper is releasing the victim's memory.
> This can result in a pointless oom killer invocation because a waiter
> might be racing with the oom_reaper
>
> P1 oom_reaper P2
> oom_reap_task mutex_lock(oom_lock)
> out_of_memory # no victim because we have one already
> __oom_reap_task_mm mute_unlock(oom_lock)
> mutex_lock(oom_lock)
> set MMF_OOM_SKIP
> select_bad_process
> # finds a new victim
>
> The page allocator prevents from this race by trying to allocate after the
> lock can be acquired (in __alloc_pages_may_oom) which acts as a last
> minute check. Moreover page allocator simply doesn't block on the
> oom_lock and simply retries the whole reclaim process.
>
> Memcg oom killer should do the last minute check as well. Call
> mem_cgroup_margin to do that. Trylock on the oom_lock could be done as
> well but this doesn't seem to be necessary at this stage.
>
> [mhocko@kernel.org: commit log]
>
> Suggested-by: Michal Hocko <mhocko@kernel.org>
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Acked-by: Chris Down <chris@chrisdown.name>
> Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Link: http://lkml.kernel.org/r/1594735034-19190-1-git-send-email-laoar.shao@gmail.com
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: zhongjiang-ali <zhongjiang-ali@linux.alibaba.com>
> ---
> mm/memcontrol.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index b30a52d..369d9e1 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1663,15 +1663,21 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
> .gfp_mask = gfp_mask,
> .order = order,
> };
> - bool ret;
> + bool ret = true;
>
> if (mutex_lock_killable(&oom_lock))
> return true;
> +
> + if (mem_cgroup_margin(memcg) >= (1 << order))
> + goto unlock;
> +
> /*
> * A few threads which were not waiting at mutex_lock_killable() can
> * fail to bail out. Therefore, check again after holding oom_lock.
> */
> ret = should_force_charge() || out_of_memory(&oc);
> +
> +unlock:
> mutex_unlock(&oom_lock);
> return ret;
> }
^ permalink raw reply [flat|nested] 2+ messages in thread
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