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From: Michal Hocko <mhocko@kernel.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, Johannes Weiner <hannes@cmpxchg.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/2] oom, memcg: do not report racy no-eligible OOM
Date: Sun, 13 Jan 2019 18:36:03 +0100	[thread overview]
Message-ID: <20190113173309.GA1578@dhcp22.suse.cz> (raw)
In-Reply-To: <0aacad13-3e91-646a-90b1-c70993b05701@i-love.sakura.ne.jp>

On Sat 12-01-19 19:52:50, Tetsuo Handa wrote:
> On 2019/01/12 1:45, Michal Hocko wrote:
> >>> Anyway, could you update your patch and abstract 
> >>> 	if (unlikely(tsk_is_oom_victim(current) ||
> >>> 		     fatal_signal_pending(current) ||
> >>> 		     current->flags & PF_EXITING))
> >>>
> >>> in try_charge and reuse it in mem_cgroup_out_of_memory under the
> >>> oom_lock with an explanation please?
> >>
> >> I don't think doing so makes sense, for
> >>
> >>   tsk_is_oom_victim(current) = T && fatal_signal_pending(current) == F
> >>
> >> can't happen for mem_cgroup_out_of_memory() under the oom_lock, and
> >> current->flags cannot get PF_EXITING when current is inside
> >> mem_cgroup_out_of_memory(). fatal_signal_pending(current) alone is
> >> appropriate for mem_cgroup_out_of_memory() under the oom_lock because
> >>
> >>   tsk_is_oom_victim(current) = F && fatal_signal_pending(current) == T
> >>
> >> can happen there.
> > 
> > I meant to use the same check consistently. If we can bypass the charge
> > under a list of conditions in the charge path we should be surely be
> > able to the the same for the oom path. I will not insist but unless
> > there is a strong reason I would prefer that.
> > 
> 
> You mean something like this? I'm not sure this change is safe.
> 
>  mm/memcontrol.c | 27 +++++++++++++++++++++++----
>  1 file changed, 23 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 17189da..1733d019 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -248,6 +248,12 @@ enum res_type {
>  	     iter != NULL;				\
>  	     iter = mem_cgroup_iter(NULL, iter, NULL))
>  
> +static inline bool can_ignore_limit(void)
> +{
> +	return tsk_is_oom_victim(current) || fatal_signal_pending(current) ||
> +		(current->flags & PF_EXITING);
> +}
> +
>  /* Some nice accessors for the vmpressure. */
>  struct vmpressure *memcg_to_vmpressure(struct mem_cgroup *memcg)
>  {
> @@ -1395,7 +1401,7 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
>  	 * A few threads which were not waiting at mutex_lock_killable() can
>  	 * fail to bail out. Therefore, check again after holding oom_lock.
>  	 */
> -	ret = fatal_signal_pending(current) || out_of_memory(&oc);
> +	ret = can_ignore_limit() || out_of_memory(&oc);
>  	mutex_unlock(&oom_lock);
>  	return ret;
>  }
> @@ -2215,9 +2230,7 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
>  	 * bypass the last charges so that they can exit quickly and
>  	 * free their memory.
>  	 */
> -	if (unlikely(tsk_is_oom_victim(current) ||
> -		     fatal_signal_pending(current) ||
> -		     current->flags & PF_EXITING))
> +	if (unlikely(can_ignore_limit()))
>  		goto force;
>  
>  	/*

I meant something as simple as this, indeed. I would just
s@can_ignore_limit@should_force_charge@ but this is a minor thing.

-- 
Michal Hocko
SUSE Labs

      reply	other threads:[~2019-01-13 17:36 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-07 14:38 [PATCH 0/2] oom, memcg: do not report racy no-eligible OOM Michal Hocko
2019-01-07 14:38 ` [PATCH 1/2] mm, oom: marks all killed tasks as oom victims Michal Hocko
2019-01-07 20:58   ` Tetsuo Handa
2019-01-08  8:11     ` Michal Hocko
2019-01-07 14:38 ` [PATCH 2/2] memcg: do not report racy no-eligible OOM tasks Michal Hocko
2019-01-07 20:59   ` Tetsuo Handa
2019-01-08  8:14     ` Michal Hocko
2019-01-08 10:39       ` Tetsuo Handa
2019-01-08 11:46         ` Michal Hocko
2019-01-08  8:35   ` kbuild test robot
2019-01-08  9:39     ` Michal Hocko
2019-01-11  0:23       ` [kbuild-all] " Rong Chen
2019-01-08 14:21 ` [PATCH 3/2] memcg: Facilitate termination of memcg OOM victims Tetsuo Handa
2019-01-08 14:38   ` Michal Hocko
2019-01-09 11:03 ` [PATCH 0/2] oom, memcg: do not report racy no-eligible OOM Michal Hocko
2019-01-09 11:34   ` Tetsuo Handa
2019-01-09 12:02     ` Michal Hocko
2019-01-10 23:59       ` Tetsuo Handa
2019-01-11 10:25         ` Tetsuo Handa
2019-01-11 11:33           ` Michal Hocko
2019-01-11 12:40             ` Tetsuo Handa
2019-01-11 13:34               ` Michal Hocko
2019-01-11 14:31                 ` Tetsuo Handa
2019-01-11 15:07                   ` Michal Hocko
2019-01-11 15:37                     ` Tetsuo Handa
2019-01-11 16:45                       ` Michal Hocko
2019-01-12 10:52                         ` Tetsuo Handa
2019-01-13 17:36                           ` Michal Hocko [this message]

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