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From: Minchan Kim <minchan@kernel.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	David Rientjes <rientjes@google.com>, <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH 2/2] mm, oom_reaper: do not mmput synchronously from the oom reaper context
Date: Fri, 20 May 2016 10:30:53 +0900	[thread overview]
Message-ID: <20160520013053.GB2224@bbox> (raw)

Forking new thread because my comment is not related to this patch's
purpose but found a thing during reading this patch.

On Tue, Apr 26, 2016 at 04:04:30PM +0200, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
> 
> Tetsuo has properly noted that mmput slow path might get blocked waiting
> for another party (e.g. exit_aio waits for an IO). If that happens the
> oom_reaper would be put out of the way and will not be able to process
> next oom victim. We should strive for making this context as reliable
> and independent on other subsystems as much as possible.
> 
> Introduce mmput_async which will perform the slow path from an async
> (WQ) context. This will delay the operation but that shouldn't be a
> problem because the oom_reaper has reclaimed the victim's address space
> for most cases as much as possible and the remaining context shouldn't
> bind too much memory anymore. The only exception is when mmap_sem
> trylock has failed which shouldn't happen too often.
> 
> The issue is only theoretical but not impossible.

The mmput_async is used for only OOM reaper which is enabled on CONFIG_MMU.
So until someone who want to use mmput_async in !CONFIG_MMU come out,
we could save sizeof(struct work_struct) per mm in !CONFIG_MMU.

WARNING: multiple messages have this Message-ID (diff)
From: Minchan Kim <minchan@kernel.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	David Rientjes <rientjes@google.com>,
	linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
	Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH 2/2] mm, oom_reaper: do not mmput synchronously from the oom reaper context
Date: Fri, 20 May 2016 10:30:53 +0900	[thread overview]
Message-ID: <20160520013053.GB2224@bbox> (raw)

Forking new thread because my comment is not related to this patch's
purpose but found a thing during reading this patch.

On Tue, Apr 26, 2016 at 04:04:30PM +0200, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
> 
> Tetsuo has properly noted that mmput slow path might get blocked waiting
> for another party (e.g. exit_aio waits for an IO). If that happens the
> oom_reaper would be put out of the way and will not be able to process
> next oom victim. We should strive for making this context as reliable
> and independent on other subsystems as much as possible.
> 
> Introduce mmput_async which will perform the slow path from an async
> (WQ) context. This will delay the operation but that shouldn't be a
> problem because the oom_reaper has reclaimed the victim's address space
> for most cases as much as possible and the remaining context shouldn't
> bind too much memory anymore. The only exception is when mmap_sem
> trylock has failed which shouldn't happen too often.
> 
> The issue is only theoretical but not impossible.

The mmput_async is used for only OOM reaper which is enabled on CONFIG_MMU.
So until someone who want to use mmput_async in !CONFIG_MMU come out,
we could save sizeof(struct work_struct) per mm in !CONFIG_MMU.

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             reply	other threads:[~2016-05-20  1:30 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-20  1:30 Minchan Kim [this message]
2016-05-20  1:30 ` [PATCH 2/2] mm, oom_reaper: do not mmput synchronously from the oom reaper context Minchan Kim
2016-05-20  6:16 ` Michal Hocko
2016-05-20  6:16   ` Michal Hocko
2016-05-20  7:12   ` Minchan Kim
2016-05-20  7:12     ` Minchan Kim
  -- strict thread matches above, loose matches on Subject: below --
2016-04-26 14:04 [PATCH 0/2] last pile of oom_reaper patches for now Michal Hocko
2016-04-26 14:04 ` [PATCH 2/2] mm, oom_reaper: do not mmput synchronously from the oom reaper context Michal Hocko
2016-04-26 14:04   ` Michal Hocko
2016-04-26 14:18   ` kbuild test robot
2016-04-26 14:58     ` Michal Hocko
2016-04-26 14:58       ` Michal Hocko
2016-05-19 14:29   ` Tetsuo Handa
2016-05-19 17:20     ` Michal Hocko
2016-05-25 10:52       ` Tetsuo Handa
2016-05-25 13:50         ` Michal Hocko
2016-05-25 14:30           ` Tetsuo Handa

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