Hi Sebastian. On Sat, Sep 26, 2026 at 07:51:46AM +0200, Sebastian Chlad <[email protected]> wrote: > test_memcontrol fails intermittently, but most of its checks fail > silently, so a "not ok" line gives no indication of how far off the > measured value was. This series makes those failures print the observed > and expected values. It does not change any threshold or pass/fail > behaviour. > > Patch 1 converts the terminal tolerance checks to values_close_report(), > as was done for test_cpu in commit 4cdde87d723a ("selftests: cgroup: Use > values_close_report in test_cpu"). values_close() is kept where it is a > loop or retry condition, where a mismatch is expected. > > Patch 2 reports the "memory.current < 50M" check in > alloc_pagecache_50M_check(). Because test_memcg_high() calls the same > helper expecting it to fail, it gets a quiet variant. An alternative > would be to pass the flag through the currently unused void *arg of > the cg_run() callback; I am happy to switch to that if preferred. > > With patch 1 applied, we observe at times failures like these: > > not ok 3 test_memcg_min > [FAIL] actual=18722816 expected=30408704 | diff=11685888 | limit=7369725 | > tolerance=15% | actual_error=23.78% > > not ok 4 test_memcg_low > [FAIL] actual=20852736 expected=30408704 | diff=9555968 | limit=7689210 | > tolerance=15% | actual_error=18.64% > > not ok 4 test_memcg_low > [FAIL] actual=14364672 expected=22020096 | diff=7655424 | limit=7276940 | > tolerance=20% | actual_error=21.04% > > These are the child memory.current checks in test_memcg_protection() > (expected ~29M and ~21M). Their tolerances were already raised in commit > d2def68ae06a ("selftests: memcg: increase error tolerance of child > memory.current check in test_memcg_protection()"), and the values above > still fall outside them. In the first case the child is about 38% below > the expected 29M. This series only makes such failures visible; whether > the expectations or the tolerances should change is left for a separate > discussion. > > Changes in v2: > - Patch 1: pass the measured value first in the alloc_anon_50M_check() > values_close_report() call, so that a failure prints actual and > expected the right way round (reported by Sashiko AI review). > > v1: > https://lore.kernel.org/all/[email protected]/ > > Sebastian Chlad (2): > selftests: cgroup: Use values_close_report in test_memcontrol > selftests: cgroup: Report memory.current shortfall in > alloc_pagecache_50M_check > > .../selftests/cgroup/test_memcontrol.c | 50 +++++++++++++------ > 1 file changed, 36 insertions(+), 14 deletions(-)
AFAIU, the test is catching two types of errors: a) running under global pressure (preparations already fail), b) mismatches in expected values of protection tests (after preparation). I like the reporting of the latter -- with (only) that all consequent silent failures would imply^H strongly hint the error of type a), no? :-) Thanks, Michal
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