linux-kernel - Re: [[PATCH v2] 2/2] futex: Only delay OOM reaper for processes using robust futex

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Message-ID: <20250804115037.19690-1-zhongjinji@honor.com>
Date: Mon, 4 Aug 2025 19:50:37 +0800
From: zhongjinji <zhongjinji@...or.com>
To: <mhocko@...e.com>
CC: <akpm@...ux-foundation.org>, <andrealmeid@...lia.com>,
	<dave@...olabs.net>, <dvhart@...radead.org>, <feng.han@...or.com>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>, <liulu.liu@...or.com>,
	<mingo@...hat.com>, <npache@...hat.com>, <peterz@...radead.org>,
	<rientjes@...gle.com>, <shakeel.butt@...ux.dev>, <tglx@...utronix.de>,
	<zhongjinji@...or.com>
Subject: Re: [[PATCH v2] 2/2] futex: Only delay OOM reaper for processes using robust futex

>On Fri 01-08-25 23:36:49, zhongjinji@...or.com wrote:
>> From: zhongjinji <zhongjinji@...or.com>
>> 
>> After merging the patch
>> https://lore.kernel.org/all/20220414144042.677008-1-npache@redhat.com/T/#u,
>> the OOM reaper runs less frequently because many processes exit within 2 seconds.
>> 
>> However, when a process is killed, timely handling by the OOM reaper allows
>> its memory to be freed faster.
>> 
>> Since relatively few processes use robust futex, delaying the OOM reaper for
>> all processes is undesirable, as many killed processes cannot release memory
>> more quickly.
>
>Could you elaborate more about why this is really needed? OOM should be
>a very slow path. Why do you care about this potential improvement in
>that situation? In other words what is the usecase?

Well, We are using the cgroup v1 freezer. When a frozen process is
killed, it cannot exit immediately and is blocked in __refrigerator until
it is thawed. When the process cannot be thawed in time, it will result in 
increased system memory pressure.