linux-kernel - Re: [PATCH v7 1/2] selftests: memcg: Allow low event with no memory.low and memory

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Message-ID: <d36jhvahtoqqtuw4y2k4rjzmxnu4ejbffvimrnffvcu3raby6l@asjm6h6r7w3k>
Date: Wed, 23 Apr 2025 18:49:36 +0200
From: Michal Koutný <mkoutny@...e.com>
To: Waiman Long <llong@...hat.com>
Cc: Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Shakeel Butt <shakeel.butt@...ux.dev>, 
	Muchun Song <muchun.song@...ux.dev>, Andrew Morton <akpm@...ux-foundation.org>, 
	Tejun Heo <tj@...nel.org>, Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org, 
	cgroups@...r.kernel.org, linux-mm@...ck.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v7 1/2] selftests: memcg: Allow low event with no
 memory.low and memory_recursiveprot on

On Tue, Apr 22, 2025 at 07:58:56PM -0400, Waiman Long <llong@...hat.com> wrote:
> Am I correct to assume that the purpose of 1d09069f5313f ("selftests:
> memcg: expect no low events in unprotected sibling") is to force a
> failure in the test_memcg_low test to force a change in the current
> behavior? Or was it the case that it didn't fail when you submit your
> patch?

Yes, the failure had been intended to mark unexpected mode of reclaim
(there's still a reproducer somewhere in the references). However, I
learnt that:
  a) it ain't easy to fix,
  b) the only occurence of the troublesome behavior was in the test and
     never reported by users in real life.

I've started to prefer the variant where the particular check is
indefinite since that.

HTH,
Michal

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