From: Michal Hocko <mhocko@kernel.org>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: akpm@linux-foundation.org, rientjes@google.com, mgorman@suse.de,
oleg@redhat.com, torvalds@linux-foundation.org, hughd@google.com,
andrea@kernel.org, riel@redhat.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/5] mm, oom_reaper: implement OOM victims queuing
Date: Sat, 6 Feb 2016 09:37:58 +0100 [thread overview]
Message-ID: <20160206083757.GB25220@dhcp22.suse.cz> (raw)
In-Reply-To: <201602061454.GDG43774.LSHtOOMFOFVJQF@I-love.SAKURA.ne.jp>
On Sat 06-02-16 14:54:24, Tetsuo Handa wrote:
> Michal Hocko wrote:
> > > But if we consider non system-wide OOM events, it is not very unlikely to hit
> > > this race. This queue is useful for situations where memcg1 and memcg2 hit
> > > memcg OOM at the same time and victim1 in memcg1 cannot terminate immediately.
> >
> > This can happen of course but the likelihood is _much_ smaller without
> > the global OOM because the memcg OOM killer is invoked from a lockless
> > context so the oom context cannot block the victim to proceed.
>
> Suppose mem_cgroup_out_of_memory() is called from a lockless context via
> mem_cgroup_oom_synchronize() called from pagefault_out_of_memory(), that
> "lockless" is talking about only current thread, doesn't it?
Yes and you need the OOM context to sit on the same lock as the victim
to form a deadlock. So while the victim might be blocked somewhere it is
much less likely it would be deadlocked.
> Since oom_kill_process() sets TIF_MEMDIE on first mm!=NULL thread of a
> victim process, it is possible that non-first mm!=NULL thread triggers
> pagefault_out_of_memory() and first mm!=NULL thread gets TIF_MEMDIE,
> isn't it?
I got lost here completely. Maybe it is your usage of thread terminology
again.
> Then, where is the guarantee that victim1 (first mm!=NULL thread in memcg1
> which got TIF_MEMDIE) is not waiting at down_read(&victim2->mm->mmap_sem)
> when victim2 (first mm!=NULL thread in memcg2 which got TIF_MEMDIE) is
> waiting at down_write(&victim2->mm->mmap_sem)
All threads/processes sharing the same mm are in fact in the same memory
cgroup. That is the reason we have owner in the task_struct
> or both victim1 and victim2
> are waiting on a lock somewhere in memory reclaim path (e.g.
> mutex_lock(&inode->i_mutex))?
Such waiting has to make a forward progress at some point in time
because the lock itself cannot be deadlocked by the memcg OOM context.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-02-06 8:38 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-03 13:13 [PATCH 0/5] oom reaper v5 Michal Hocko
2016-02-03 13:13 ` [PATCH 1/5] mm, oom: introduce oom reaper Michal Hocko
2016-02-03 23:48 ` David Rientjes
2016-02-04 6:41 ` Michal Hocko
2016-02-06 13:22 ` Tetsuo Handa
2016-02-15 20:50 ` Michal Hocko
2016-02-03 13:13 ` [PATCH 2/5] oom reaper: handle mlocked pages Michal Hocko
2016-02-03 23:57 ` David Rientjes
2016-02-23 1:36 ` David Rientjes
2016-02-23 13:21 ` Michal Hocko
2016-02-29 3:19 ` Hugh Dickins
2016-02-29 13:41 ` Michal Hocko
2016-03-08 13:40 ` Michal Hocko
2016-03-08 20:07 ` Hugh Dickins
2016-03-09 8:26 ` Michal Hocko
2016-02-03 13:13 ` [PATCH 3/5] oom: clear TIF_MEMDIE after oom_reaper managed to unmap the address space Michal Hocko
2016-02-04 14:22 ` Tetsuo Handa
2016-02-04 14:43 ` Michal Hocko
2016-02-04 15:08 ` Tetsuo Handa
2016-02-04 16:31 ` Michal Hocko
2016-02-05 11:14 ` Tetsuo Handa
2016-02-06 8:30 ` Michal Hocko
2016-02-06 11:23 ` Tetsuo Handa
2016-02-15 20:47 ` Michal Hocko
2016-02-06 6:45 ` Michal Hocko
2016-02-06 14:33 ` Tetsuo Handa
2016-02-15 20:40 ` [PATCH 3.1/5] oom: make oom_reaper freezable Michal Hocko
2016-02-03 13:13 ` [PATCH 4/5] mm, oom_reaper: report success/failure Michal Hocko
2016-02-03 23:10 ` David Rientjes
2016-02-04 6:46 ` Michal Hocko
2016-02-04 22:31 ` David Rientjes
2016-02-05 9:26 ` Michal Hocko
2016-02-06 6:34 ` Michal Hocko
2016-02-03 13:14 ` [PATCH 5/5] mm, oom_reaper: implement OOM victims queuing Michal Hocko
2016-02-04 10:49 ` Tetsuo Handa
2016-02-04 14:53 ` Michal Hocko
2016-02-06 5:54 ` Tetsuo Handa
2016-02-06 8:37 ` Michal Hocko [this message]
2016-02-06 15:33 ` Tetsuo Handa
2016-02-15 20:15 ` Michal Hocko
2016-02-16 11:11 ` Tetsuo Handa
2016-02-16 15:53 ` Michal Hocko
2016-02-17 9:48 ` [PATCH 6/5] oom, oom_reaper: disable oom_reaper for Michal Hocko
2016-02-17 10:41 ` Tetsuo Handa
2016-02-17 11:33 ` Michal Hocko
2016-02-19 18:34 ` Michal Hocko
2016-02-20 2:32 ` [PATCH 6/5] oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task Tetsuo Handa
2016-02-22 9:41 ` Michal Hocko
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