On 11/20/25 13:40, Lance Yang wrote:
On 2025/11/20 11:16, 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.
Suggested-by: Lance Yang lance.yang@linux.dev Signed-off-by: Guopeng Zhang zhangguopeng@kylinos.cn
v2: - Mention the periodic rstat flush interval (FLUSH_TIME = 2*HZ) in the comment and clarify the rationale for the 3s timeout. - Replace the hard-coded retry count and wait interval with macros to avoid magic numbers and make the 3s timeout calculation explicit.
.../selftests/cgroup/test_memcontrol.c | 30 ++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c index 4e1647568c5b..7bea656658a2 100644 --- a/tools/testing/selftests/cgroup/test_memcontrol.c +++ b/tools/testing/selftests/cgroup/test_memcontrol.c @@ -24,6 +24,9 @@ static bool has_localevents; static bool has_recursiveprot; +#define MEMCG_SOCKSTAT_WAIT_RETRIES 30 /* 3s total */ +#define MEMCG_SOCKSTAT_WAIT_INTERVAL_US (100 * 1000) /* 100 ms */
Nit: Defines are usually placed at the top of the file (e.g., after the #include block). Placing them between global variables and functions looks a bit out of place, IMHO ... Otherwise, feel free to add:
Reviewed-by: Lance Yang lance.yang@linux.dev [...]
Cheers, Lance
Thanks for the review and the suggestion!
Good point about the placement of the defines — I’ll move MEMCG_SOCKSTAT_WAIT_* after the #include block in v3 as you suggested, and I’ll add your:
Reviewed-by: Lance Yang lance.yang@linux.dev
as well.
Thanks again!
Best regards, Guopeng