Re: [PATCHSET cgroup/for-3.12] cgroup: make cgroup_event specific tomemcg

From: Michal Hocko
Date: Mon Aug 05 2013 - 12:01:18 EST

On Sun 04-08-13 12:07:21, Tejun Heo wrote:
> Hello,

Hi Tejun,

> Like many other things in cgroup, cgroup_event is way too flexible and
> complex - it strives to provide completely flexible event monitoring
> facility in cgroup proper which allows any number of users to monitor
> custom events. This is overboard, to say the least,

Could you be more specific about what is so "overboard" about this
interface? I am not familiar with internals much, so I cannot judge the
complexity part, but I thought that eventfd was intended for this kind
of kernel->userspace notifications.

> and I strongly think that cgroup should not any new usages of this
> facility and preferably deprecate the existing usages if at all
> possible.

So you think that vmpressure, oom notification or thresholds are
an abuse of this interface? What would you consider a reasonable
replacement for those notifications? Or do you think that controller
shouldn't be signaling any conditions to the userspace at all?

Michal Hocko
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