On Mon, Sep 11, 2017 at 01:48:39PM -0700, David Rientjes wrote:

On Mon, 11 Sep 2017, Roman Gushchin wrote:

quoted

Add a "groupoom" cgroup v2 mount option to enable the cgroup-aware
OOM killer. If not set, the OOM selection is performed in
a "traditional" per-process way.

The behavior can be changed dynamically by remounting the cgroupfs.

I can't imagine that Tejun would be happy with a new mount option, 
especially when it's not required.

OOM behavior does not need to be defined at mount time and for the entire 
hierarchy.  It's possible to very easily implement a tunable as part of 
mem cgroup that is propagated to descendants and controls the oom scoring 
behavior for that hierarchy.  It does not need to be system wide and 
affect scoring of all processes based on which mem cgroup they are 
attached to at any given time.

No, I don't think that mixing per-cgroup and per-process OOM selection
algorithms is a good idea.

So, there are 3 reasonable options:
1) boot option
2) sysctl
3) cgroup mount option

I believe, 3) is better, because it allows changing the behavior dynamically,
and explicitly depends on v2 (what sysctl lacks).

So, the only question is should it be opt-in or opt-out option.
Personally, I would prefer opt-out, but Michal has a very strong opinion here.

Thanks!

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