Re: [PATCH 0/7] selftests: memcg: Fix test_memcontrol test failures with large page sizes

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 19 Mar 2026 13:37:45 -0400 Waiman Long <longman@redhat.com> wrote:

> There are a number of test failures with the running of the
> test_memcontrol selftest on a 128-core arm64 system on kernels with
> 4k/16k/64k page sizes. This patch series makes some minor changes to
> the kernel and the test_memcontrol selftest to address these failures.
> 
> The first kernel patch scales the memcg vmstats flush threshold
> logarithmetically instead of linearly with the total number of CPUs. The
> second kernel patch scale down MEMCG_CHARGE_BATCH with increases in page
> size. These 2 patches help to reduce the discrepancies between the
> reported usage data with the real ones.
> 
> The next 5 test_memcontrol selftest patches adjust the testing code to
> greatly reduce the chance that it will report failure, though some
> occasional failures is still possible.
> 
> To verify the changes, the test_memcontrol selftest was run 100
> times each on a 128-core arm64 system on kernels with 4k/16k/64k
> page sizes.  No failure was observed other than some failures of the
> test_memcg_reclaim test when running on a 16k page size kernel. The
> reclaim_until() call failed because of the unexpected over-reclaim of
> memory. This will need a further look but it happens with the 16k page
> size kernel only and I don't have a production ready kernel config file
> to use in buildinig this 16k page size kernel. The new test_memcontrol
> selftest and kernel were also run on a 96-core x86 system to make sure
> there was no regression.

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