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

David Vernet
2022-04-23T11:37:00Z

On Fri, Apr 22, 2022 at 04:14:49PM -0700, Roman Gushchin wrote:
> 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.

Ack, will fix in a follow-on patch.

>
> > + 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;

Agreed that's a bit clearer, I'll include this in the follow-on patch.