Re: [PATCH 3/5] cgroup: Account for memory_localevents in test_memcg_oom_group_leaf_events()

Roman Gushchin
2022-04-22T23:30:40Z

On Fri, Apr 22, 2022 at 08:57:27AM -0700, David Vernet wrote:
> The test_memcg_oom_group_leaf_events() testcase in the cgroup memcg tests
> validates that processes in a group that perform allocations exceeding
> memory.oom.group are killed. It also validates that the
> memory.events.oom_kill events are properly propagated in this case. Commit
> 06e11c907ea4 ("kselftests: memcg: update the oom group leaf events test")
> fixed test_memcg_oom_group_leaf_events() to account for the fact that the
> memory.events.oom_kill events in a child cgroup is propagated up to its
> parent. This behavior can actually be configured by the memory_localevents
> mount option, so this patch updates the testcase to properly account for
> the possible presence of this mount option.
>
> Signed-off-by: David Vernet <void@manifault.com>
> ---
> .../testing/selftests/cgroup/test_memcontrol.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c
> index ea2fd27e52df..d88e0ca3f3d1 100644
> --- a/tools/testing/selftests/cgroup/test_memcontrol.c
> +++ b/tools/testing/selftests/cgroup/test_memcontrol.c
> @@ -21,6 +21,7 @@
> #include "../kselftest.h"
> #include "cgroup_util.h"
>
> +static bool has_localevents;
> static bool has_recursiveprot;
>
> /*
> @@ -1091,6 +1092,7 @@ static int test_memcg_oom_group_leaf_events(const char *root)
> {
> int ret = KSFT_FAIL;
> char *parent, *child;
> + long parent_oom_events;
>
> parent = cg_name(root, "memcg_test_0");
> child = cg_name(root, "memcg_test_0/memcg_test_1");
> @@ -1128,7 +1130,15 @@ static int test_memcg_oom_group_leaf_events(const char *root)
> if (cg_read_key_long(child, "memory.events", "oom_kill ") <= 0)
> goto cleanup;
>
> - if (cg_read_key_long(parent, "memory.events", "oom_kill ") <= 0)
> + parent_oom_events = cg_read_key_long(
> + parent, "memory.events", "oom_kill ");
> + // If memory_localevents is not enabled (the default), the parent should
> + // count OOM events in its children groups. Otherwise, it should not
> + // have observed any events.

Please, use /* */ style comments, it's a generic kernel style.

> + if (has_localevents) {
> + if (parent_oom_events != 0)
> + goto cleanup;
> + } else if (parent_oom_events <= 0)
> goto cleanup;

How about something like this? IMO a bit more clear what's going on.
if ((has_local_events && parent_oom_events == 0) ||
parent_oom_events > 0)
ret = KSFT_PASS;

Anyway, looks good to me.
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>

>
> ret = KSFT_PASS;
> @@ -1298,6 +1308,11 @@ int main(int argc, char **argv)
> ksft_exit_skip("Failed to query cgroup mount option\n");
> has_recursiveprot = proc_status;
>
> + proc_status = proc_mount_contains("memory_localevents");
> + if (proc_status < 0)
> + ksft_exit_skip("Failed to query cgroup mount option\n");
> + has_localevents = proc_status;
> +
> for (i = 0; i < ARRAY_SIZE(tests); i++) {
> switch (tests[i].fn(root)) {
> case KSFT_PASS:
> --
> 2.30.2
>