On 11/27/25 18:55, Lance Yang wrote:
>
>
> On 2025/11/24 20:38, 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"
>
> This patch fails to apply to mm-new ...
>
> Hmm, it expects #include "kselftest.h" here, but the tree uses
> #include "../kselftest.h".
>
> Which is odd, as that line hasn't been touched in years ...
Hi,lance
Thanks for your review.
When I prepared this patch I was working on linux-next, where
tools/testing/selftests/cgroup/test_memcontrol.c already uses:
#include "kselftest.h"
I just checked, and this change comes from the following commit:
1aaedc385b9b278dcf91f4e9d0c3e1a078804ff1
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20251127&id=1aaedc385b9b278dcf91f4e9d0c3e1a078804ff1
So the patch applies cleanly on top of the latest linux-next, but not on
mm-new which still has `#include "../kselftest.h"`.
Thanks,
Guopeng
