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 <[email protected]>
Signed-off-by: Guopeng Zhang <[email protected]>
---
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 <[email protected]>
[...]
Cheers,
Lance
