On Wed, Dec 03, 2025 at 07:56:30PM +0800, Guopeng Zhang zhangguopeng@kylinos.cn 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 zhangguopeng@kylinos.cn Suggested-by: Lance Yang lance.yang@linux.dev Reviewed-by: Shakeel Butt shakeel.butt@linux.dev
.../selftests/cgroup/test_memcontrol.c | 20 ++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-)
Acked-by: Michal Koutný mkoutny@suse.com