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SubjectRe: [PATCH] mm/oom_kill: count global and memory cgroup oom kills
2017-05-19 15:22 GMT+01:00 Konstantin Khlebnikov <khlebnikov@yandex-team.ru>:
> Show count of global oom killer invocations in /proc/vmstat and
> count of oom kills inside memory cgroup in knob "memory.events"
> (in memory.oom_control for v1 cgroup).
>
> Also describe difference between "oom" and "oom_kill" in memory
> cgroup documentation. Currently oom in memory cgroup kills tasks
> iff shortage has happened inside page fault.
>
> These counters helps in monitoring oom kills - for now
> the only way is grepping for magic words in kernel log.
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> ---
> Documentation/cgroup-v2.txt | 12 +++++++++++-
> include/linux/memcontrol.h | 1 +
> include/linux/vm_event_item.h | 1 +
> mm/memcontrol.c | 2 ++
> mm/oom_kill.c | 6 ++++++
> mm/vmstat.c | 1 +
> 6 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
> index dc5e2dcdbef4..a742008d76aa 100644
> --- a/Documentation/cgroup-v2.txt
> +++ b/Documentation/cgroup-v2.txt
> @@ -830,9 +830,19 @@ PAGE_SIZE multiple when read back.
>
> oom
>
> + The number of time the cgroup's memory usage was
> + reached the limit and allocation was about to fail.
> + Result could be oom kill, -ENOMEM from any syscall or
> + completely ignored in cases like disk readahead.
> + For now oom in memory cgroup kills tasks iff shortage
> + has happened inside page fault.

From a user's point of view the difference between "oom" and "max"
becomes really vague here,
assuming that "max" is described almost in the same words:

"The number of times the cgroup's memory usage was
about to go over the max boundary. If direct reclaim
fails to bring it down, the OOM killer is invoked."

I wonder, if it's better to fix the existing "oom" value to show what
it has to show, according to docs,
rather than to introduce a new one?

> +
> + oom_kill
> +
> The number of times the OOM killer has been invoked in
> the cgroup. This may not exactly match the number of
> - processes killed but should generally be close.
> + processes killed but should generally be close: each
> + invocation could kill several processes at once.
>
> memory.stat
>

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