linux-kernel - Re: [PATCH 2/2] selftests: cgroup: fix unexpected failure on test_memcg

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Message-ID: <r5owzlvxbx22gqmw2cnmykvrzzhhw3hkoffk3f4wbvv7lmqzod@wbbmnt4a76cu>
Date:   Tue, 23 May 2023 16:40:46 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     Haifeng Xu <haifeng.xu@...pee.com>
Cc:     mhocko@...nel.org, roman.gushchin@...ux.dev, hannes@...xchg.org,
        shakeelb@...gle.com, akpm@...ux-foundation.org,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] selftests: cgroup: fix unexpected failure on
 test_memcg_low

On Mon, May 22, 2023 at 09:52:33AM +0000, Haifeng Xu <haifeng.xu@...pee.com> wrote:
> Since commit f079a020ba95 ("selftests: memcg: factor out common parts
> of memory.{low,min} tests"), the value used in second alloc_anon has
> changed from 148M to 170M. Because memory.low allows reclaiming page
> cache in child cgroups, so the memory.current is close to 30M instead
> of 50M. Therefore, adjust the expected value of parent cgroup.
> 
> Fixes: f079a020ba95 ("selftests: memcg: factor out common parts of memory.{low,min} tests")
> Signed-off-by: Haifeng Xu <haifeng.xu@...pee.com>
> ---
>  tools/testing/selftests/cgroup/test_memcontrol.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Yes, the expected value should be complement of the allocation to the
limit when reclaim is allowed.

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

FTR, the test_memcg_low fails after the fix still (6.3.1-2-default)
because of nonzero memory.events:low in the unprotected A/B/E group
(with memory_recursiveprot).
(That's another and long standing issues -- perhaps the reason why this
issue was hidden.)

Thanks,
Michal

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