linux-kernel - Re: [PATCH v4 2/3] mm/oom_kill: Only delay OOM reaper for processes using robust futexes

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Message-ID: <aKIvd4ZCdWUEpBT_@tiehlicka>
Date: Sun, 17 Aug 2025 21:37:27 +0200
From: Michal Hocko <mhocko@...e.com>
To: zhongjinji@...or.com
Cc: linux-mm@...ck.org, akpm@...ux-foundation.org, rientjes@...gle.com,
	shakeel.butt@...ux.dev, npache@...hat.com,
	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
	peterz@...radead.org, dvhart@...radead.org, dave@...olabs.net,
	andrealmeid@...lia.com, liam.howlett@...cle.com,
	liulu.liu@...or.com, feng.han@...or.com
Subject: Re: [PATCH v4 2/3] mm/oom_kill: Only delay OOM reaper for processes
 using robust futexes

On Thu 14-08-25 21:55:54, zhongjinji@...or.com wrote:
> From: zhongjinji <zhongjinji@...or.com>
> 
> The OOM reaper can quickly reap a process's memory when the system encounters
> OOM, helping the system recover. Without the OOM reaper, if a process frozen
> by cgroup v1 is OOM killed, the victims' memory cannot be freed, and the
> system stays in a poor state. Even if the process is not frozen by cgroup v1,
> reaping victims' memory is still meaningful, because having one more process
> working speeds up memory release.
> 
> When processes holding robust futexes are OOM killed but waiters on those
> futexes remain alive, the robust futexes might be reaped before
> futex_cleanup() runs. It would cause the waiters to block indefinitely.
> To prevent this issue, the OOM reaper's work is delayed by 2 seconds [1].
> The OOM reaper now rarely runs since many killed processes exit within 2
> seconds.
> 
> Because robust futex users are few, it is unreasonable to delay OOM reap for
> all victims. For processes that do not hold robust futexes, the OOM reaper
> should not be delayed and for processes holding robust futexes, the OOM
> reaper must still be delayed to prevent the waiters to block indefinitely [1].
> 
> Link: https://lore.kernel.org/all/20220414144042.677008-1-npache@redhat.com/T/#u [1]

What has happened to
https://lore.kernel.org/all/aJGiHyTXS_BqxoK2@tiehlicka/T/#u ?

Generally speaking it would be great to provide a link to previous
versions of the patchset. I do not see v3 in my inbox (which is quite
messy ATM so I might have easily missed it).
-- 
Michal Hocko
SUSE Labs