linux-kernel - Re: [PATCH v8 1/2] selftests: memcg: Allow low event with no memory.low and memory

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Message-ID: <vki6asa3arxitfgio3goox6hiyzmytxskoje6e2z55j3xrskly@4jq4btqz5nwd>
Date: Fri, 2 May 2025 11:43:02 +0200
From: Michal Koutný <mkoutny@...e.com>
To: Waiman Long <longman@...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 v8 1/2] selftests: memcg: Allow low event with no
 memory.low and memory_recursiveprot on

On Thu, May 01, 2025 at 09:04:42PM -0400, Waiman Long <longman@...hat.com> wrote:
> Modify the test_memcontrol.c to ignore low event in the 3rd child cgroup
> with memory_recursiveprot on.
> 
> The 4th child cgroup has no memory usage and so has an effective
> low of 0. It has no low event count because the mem_cgroup_below_low()
> check in shrink_node_memcgs() is skipped as mem_cgroup_below_min()
> returns true. If we ever change mem_cgroup_below_min() in such a way
> that it no longer skips the no usage case, we will have to add code to
> explicitly skip it.
> 
> With this patch applied, the test_memcg_low sub-test finishes
> successfully without failure in most cases. Though both test_memcg_low
> and test_memcg_min sub-tests may still fail occasionally if the
> memory.current values fall outside of the expected ranges.
> 
> Suggested-by: Michal Koutný <mkoutny@...e.com>
> Signed-off-by: Waiman Long <longman@...hat.com>

Acked-by: Michal Koutný <mkoutny@...e.com>

(Thank you. Not sure if this can be both with Suggested-by, so either of
them alone is fine by me.)


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