Re: [PATCH] memcg, oom: move out_of_memory back to the charge path

[Greg Thelen]

Michal Hocko <mhocko@xxxxxxxxxx> wrote:

> On Thu 28-06-18 16:19:07, Greg Thelen wrote:
>> Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> [...]
>> > +	if (mem_cgroup_out_of_memory(memcg, mask, order))
>> > +		return OOM_SUCCESS;
>> > +
>> > +	WARN(1,"Memory cgroup charge failed because of no reclaimable memory! "
>> > +		"This looks like a misconfiguration or a kernel bug.");
>> 
>> I'm not sure here if the warning should here or so strongly worded.  It
>> seems like the current task could be oom reaped with MMF_OOM_SKIP and
>> thus mem_cgroup_out_of_memory() will return false.  So there's nothing
>> alarming in that case.
>
> If the task is reaped then its charges should be released as well and
> that means that we should get below the limit. Sure there is some room
> for races but this should be still unlikely. Maybe I am just
> underestimating though.
>
> What would you suggest instead?

I suggest checking MMF_OOM_SKIP or deleting the warning.  But I don't
feel strongly.