The quilt patch titled Subject: selftests: memcg: Increase error tolerance of child memory.current check in test_memcg_protection() has been removed from the -mm tree. Its filename was selftests-memcg-increase-error-tolerance-of-child-memorycurrent-check-in-test_memcg_protection.patch This patch was dropped because an updated version will be issued ------------------------------------------------------ From: Waiman Long Subject: selftests: memcg: Increase error tolerance of child memory.current check in test_memcg_protection() Date: Tue, 15 Apr 2025 17:04:15 -0400 The test_memcg_protection() function is used for the test_memcg_min and test_memcg_low sub-tests. This function generates a set of parent/child cgroups like: parent: memory.min/low = 50M child 0: memory.min/low = 75M, memory.current = 50M child 1: memory.min/low = 25M, memory.current = 50M child 2: memory.min/low = 0, memory.current = 50M After applying memory pressure, the function expects the following actual memory usages. parent: memory.current ~= 50M child 0: memory.current ~= 29M child 1: memory.current ~= 21M child 2: memory.current ~= 0 In reality, the actual memory usages can differ quite a bit from the expected values. It uses an error tolerance of 10% with the values_close() helper. Both the test_memcg_min and test_memcg_low sub-tests can fail sporadically because the actual memory usage exceeds the 10% error tolerance. Below are a sample of the usage data of the tests runs that fail. Child Actual usage Expected usage %err ----- ------------ -------------- ---- 1 16990208 22020096 -12.9% 1 17252352 22020096 -12.1% 0 37699584 30408704 +10.7% 1 14368768 22020096 -21.0% 1 16871424 22020096 -13.2% The current 10% error tolerenace might be right at the time test_memcontrol.c was first introduced in v4.18 kernel, but memory reclaim have certainly evolved quite a bit since then which may result in a bit more run-to-run variation than previously expected. Increase the error tolerance to 15% for child 0 and 20% for child 1 to minimize the chance of this type of failure. The tolerance is bigger for child 1 because an upswing in child 0 corresponds to a smaller %err than a similar downswing in child 1 due to the way %err is used in values_close(). Before this patch, a 100 test runs of test_memcontrol produced the following results: 17 not ok 1 test_memcg_min 22 not ok 2 test_memcg_low After applying this patch, there were no test failure for test_memcg_min and test_memcg_low in 100 test runs. However, these tests may still fail once in a while if the memory usage goes beyond the newly extended range. Link: https://lkml.kernel.org/r/20250415210415.13414-3-longman@redhat.com Signed-off-by: Waiman Long Cc: Johannes Weiner Cc: Michal Hocko Cc: Michal Koutný Cc: Muchun Song Cc: Roman Gushchin Cc: Shakeel Butt Cc: Shuah Khan Cc: Tejun Heo Signed-off-by: Andrew Morton --- tools/testing/selftests/cgroup/test_memcontrol.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/tools/testing/selftests/cgroup/test_memcontrol.c~selftests-memcg-increase-error-tolerance-of-child-memorycurrent-check-in-test_memcg_protection +++ a/tools/testing/selftests/cgroup/test_memcontrol.c @@ -495,10 +495,10 @@ static int test_memcg_protection(const c for (i = 0; i < ARRAY_SIZE(children); i++) c[i] = cg_read_long(children[i], "memory.current"); - if (!values_close(c[0], MB(29), 10)) + if (!values_close(c[0], MB(29), 15)) goto cleanup; - if (!values_close(c[1], MB(21), 10)) + if (!values_close(c[1], MB(21), 20)) goto cleanup; if (c[3] != 0) _ Patches currently in -mm which might be from longman@redhat.com are selftests-memcg-allow-low-event-with-no-memorylow-and-memory_recursiveprot-on.patch