From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Michal Hocko <mhocko@kernel.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch] mm, oom: prevent soft lockup on memcg oom for UP systems
Date: Fri, 13 Mar 2020 09:15:09 +0900 [thread overview]
Message-ID: <202003130015.02D0F9uT079462@www262.sakura.ne.jp> (raw)
In-Reply-To: <alpine.DEB.2.21.2003121101030.158939@chino.kir.corp.google.com>
David Rientjes wrote:
> > By the way, will you share the reproducer (and how to use the reproducer) ?
> >
>
> On an UP kernel with swap disabled, you limit a memcg to 100MB and start
> three processes that each fault 40MB attached to it. Same reproducer as
> the "mm, oom: make a last minute check to prevent unnecessary memcg oom
> kills" patch except in that case there are two cores.
>
I'm not a heavy memcg user. Please provide steps for reproducing your problem
in a "copy and pastable" way (e.g. bash script, C program).
> > @@ -1576,6 +1576,7 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
> > */
> > ret = should_force_charge() || out_of_memory(&oc);
> > mutex_unlock(&oom_lock);
> > + schedule_timeout_killable(1);
> > return ret;
> > }
> >
>
> If current was process chosen for oom kill, this would actually induce the
> problem, not fix it.
>
Why? Memcg OOM path allows using forced charge path if should_force_charge() == true.
Since your lockup report
Call Trace:
shrink_node+0x40d/0x7d0
do_try_to_free_pages+0x13f/0x470
try_to_free_mem_cgroup_pages+0x16d/0x230
try_charge+0x247/0xac0
mem_cgroup_try_charge+0x10a/0x220
mem_cgroup_try_charge_delay+0x1e/0x40
handle_mm_fault+0xdf2/0x15f0
do_user_addr_fault+0x21f/0x420
page_fault+0x2f/0x40
says that allocating thread was calling try_to_free_mem_cgroup_pages() from try_charge(),
allocating thread must be able to reach mem_cgroup_out_of_memory() from mem_cgroup_oom()
from try_charge(). And actually
Memory cgroup out of memory: Killed process 808 (repro) total-vm:41944kB, anon-rss:35344kB, file-rss:504kB, shmem-rss:0kB, UID:0 pgtables:108kB oom_score_adj:0
says that allocating thread did reach mem_cgroup_out_of_memory(). Then, allocating thread
must be able to sleep at mem_cgroup_out_of_memory() if schedule_timeout_killable(1) is
mem_cgroup_out_of_memory().
Also, if current process was chosen for OOM-kill, current process will be able to leave
try_charge() due to should_force_charge() == true, won't it?
Thus, how can "this would actually induce the problem, not fix it." happen?
If your problem is that something keeps allocating threads away from reaching
should_force_charge() check, please explain the mechanism. If that is explained,
I would agree that schedule_timeout_killable(1) in mem_cgroup_out_of_memory()
won't help.
next prev parent reply other threads:[~2020-03-13 0:15 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-10 21:39 [patch] mm, oom: prevent soft lockup on memcg oom for UP systems David Rientjes
2020-03-10 22:05 ` Tetsuo Handa
2020-03-10 22:55 ` David Rientjes
2020-03-11 9:34 ` Tetsuo Handa
2020-03-11 19:38 ` David Rientjes
2020-03-11 22:04 ` Tetsuo Handa
2020-03-11 22:14 ` David Rientjes
2020-03-12 0:12 ` Tetsuo Handa
2020-03-12 18:07 ` David Rientjes
2020-03-12 22:32 ` Andrew Morton
2020-03-16 9:31 ` Michal Hocko
2020-03-16 10:04 ` Tetsuo Handa
2020-03-16 10:14 ` Michal Hocko
2020-03-13 0:15 ` Tetsuo Handa [this message]
2020-03-13 22:01 ` David Rientjes
2020-03-13 23:15 ` Tetsuo Handa
2020-03-13 23:32 ` Tetsuo Handa
2020-03-16 23:59 ` David Rientjes
2020-03-17 3:18 ` Tetsuo Handa
2020-03-17 4:09 ` David Rientjes
2020-03-18 0:55 ` [patch v2] " David Rientjes
2020-03-18 9:42 ` Michal Hocko
2020-03-18 21:40 ` David Rientjes
2020-03-18 22:03 ` [patch v3] " David Rientjes
2020-03-19 7:09 ` Michal Hocko
2020-03-12 4:23 ` [patch] " Tetsuo Handa
2020-03-10 22:10 ` Michal Hocko
2020-03-10 23:02 ` David Rientjes
2020-03-11 8:27 ` Michal Hocko
2020-03-11 19:45 ` David Rientjes
2020-03-12 8:32 ` Michal Hocko
2020-03-12 18:20 ` David Rientjes
2020-03-12 20:16 ` Michal Hocko
2020-03-16 9:32 ` Michal Hocko
2020-03-11 0:18 ` Andrew Morton
2020-03-11 0:34 ` David Rientjes
2020-03-11 8:36 ` Michal Hocko
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