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
prev parent 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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