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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Michal Hocko <mhocko@kernel.org>
Cc: "Arkadiusz Miśkiewicz" <a.miskiewicz@gmail.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Tejun Heo" <tj@kernel.org>,
	cgroups@vger.kernel.org, "Aleksa Sarai" <asarai@suse.de>,
	"Jay Kamat" <jgkamat@fb.com>, "Roman Gushchin" <guro@fb.com>,
	"Johannes Weiner" <hannes@cmpxchg.org>,
	linux-kernel@vger.kernel.org,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH v2] oom, oom_reaper: do not enqueue same task twice
Date: Sun, 27 Jan 2019 19:56:06 +0900
Message-ID: <ec0d0580-a2dd-f329-9707-0cb91205a216@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20190127083724.GA18811@dhcp22.suse.cz>

On 2019/01/27 17:37, Michal Hocko wrote:
> Thanks for the analysis and the patch. This should work, I believe but
> I am not really thrilled to overload the meaning of the MMF_UNSTABLE.
> The flag is meant to signal accessing address space is not stable and it
> is not aimed to synchronize oom reaper with the oom path.
> 
> Can we make use mark_oom_victim directly? I didn't get to think that
> through right now so I might be missing something but this should
> prevent repeating queueing as well.

Yes, TIF_MEMDIE would work. But you are planning to remove TIF_MEMDIE. Also,
TIF_MEMDIE can't avoid enqueuing many threads sharing mm_struct to the OOM
reaper. There is no need to enqueue many threads sharing mm_struct because
the OOM reaper acts on mm_struct rather than task_struct. Thus, enqueuing
based on per mm_struct flag sounds better, but MMF_OOM_VICTIM cannot be
set from wake_oom_reaper(victim) because victim's mm might be already inside
exit_mmap() when wake_oom_reaper(victim) is called after task_unlock(victim).

We could reintroduce MMF_OOM_KILLED in commit 855b018325737f76
("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task")
if you don't like overloading the meaning of the MMF_UNSTABLE. But since
MMF_UNSTABLE is available in Linux 4.9+ kernels (which covers all LTS stable
versions with the OOM reaper support), we can temporarily use MMF_UNSTABLE
for ease of backporting.

  reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <df806a77-3327-9db5-8be2-976fde1c84e5@gmail.com>
     [not found] ` <20190117122535.njcbqhlmzozdkncw@mikami>
     [not found]   ` <1d36b181-cbaf-6694-1a31-2f7f55d15675@gmail.com>
     [not found]     ` <96ef6615-a5df-30af-b4dc-417a18ca63f1@gmail.com>
     [not found]       ` <1cdbef13-564d-61a6-95f4-579d2cad243d@gmail.com>
     [not found]         ` <20190125163731.GJ50184@devbig004.ftw2.facebook.com>
     [not found]           ` <a95d004a-4358-7efc-6d21-12aac4411b32@gmail.com>
     [not found]             ` <480296c4-ed7a-3265-e84a-298e42a0f1d5@I-love.SAKURA.ne.jp>
     [not found]               ` <6da6ca69-5a6e-a9f6-d091-f89a8488982a@gmail.com>
     [not found]                 ` <72aa8863-a534-b8df-6b9e-f69cf4dd5c4d@i-love.sakura.ne.jp>
     [not found]                   ` <33a07810-6dbc-36be-5bb6-a279773ccf69@i-love.sakura.ne.jp>
     [not found]                     ` <34e97b46-0792-cc66-e0f2-d72576cdec59@i-love.sakura.ne.jp>
     [not found]                       ` <2b0c7d6c-c58a-da7d-6f0a-4900694ec2d3@gmail.com>
2019-01-26 13:10                         ` Tetsuo Handa
2019-01-26 13:10                           ` Tetsuo Handa
2019-01-27  8:37                           ` Michal Hocko
2019-01-27 10:56                             ` Tetsuo Handa [this message]
2019-01-27 11:40                               ` Michal Hocko
2019-01-27 14:57                                 ` [PATCH v3] " Tetsuo Handa
2019-01-27 14:57                                   ` Tetsuo Handa
2019-01-27 16:58                                   ` Michal Hocko
2019-01-27 23:00                                   ` Roman Gushchin
2019-01-28 18:15                                   ` Andrew Morton
2019-01-28 18:42                                     ` Michal Hocko
2019-01-28 21:53                                   ` Johannes Weiner
2019-01-29 10:34                                     ` Tetsuo Handa

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