On Mon, Nov 24, 2025 at 08:38:15PM +0800, Guopeng Zhang wrote: > test_memcg_sock() currently requires that memory.stat's "sock " counter > is exactly zero immediately after the TCP server exits. On a busy system > this assumption is too strict: > > - Socket memory may be freed with a small delay (e.g. RCU callbacks). > - memcg statistics are updated asynchronously via the rstat flushing > worker, so the "sock " value in memory.stat can stay non-zero for a > short period of time even after all socket memory has been uncharged. > > As a result, test_memcg_sock() can intermittently fail even though socket > memory accounting is working correctly. > > Make the test more robust by polling memory.stat for the "sock " > counter and allowing it some time to drop to zero instead of checking > it only once. The timeout is set to 3 seconds to cover the periodic > rstat flush interval (FLUSH_TIME = 2*HZ by default) plus some > scheduling slack. If the counter does not become zero within the > timeout, the test still fails as before. > > On my test system, running test_memcontrol 50 times produced: > > - Before this patch: 6/50 runs passed. > - After this patch: 50/50 runs passed. > > Signed-off-by: Guopeng Zhang <[email protected]> > Suggested-by: Lance Yang <[email protected]> > --- > .../selftests/cgroup/test_memcontrol.c | 20 ++++++++++++++++++- > 1 file changed, 19 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c > b/tools/testing/selftests/cgroup/test_memcontrol.c > index 4e1647568c5b..dda12e5c6457 100644 > --- a/tools/testing/selftests/cgroup/test_memcontrol.c > +++ b/tools/testing/selftests/cgroup/test_memcontrol.c > @@ -21,6 +21,8 @@ > #include "kselftest.h" > #include "cgroup_util.h" > > +#define MEMCG_SOCKSTAT_WAIT_RETRIES 30 /* 3s total */
No need for the comment at the end as it will be stale when someone change DEFAULT_WAIT_INTERVAL_US in future. Anyways it's a nit. Reviewed-by: Shakeel Butt <[email protected]>
