linux-kernel - Re: [PATCHSET cgroup/for-3.12] cgroup: make cgroup

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Message-ID: <20130805160107.GM10146@dhcp22.suse.cz>
Date:	Mon, 5 Aug 2013 18:01:07 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Tejun Heo <tj@...nel.org>
Cc:	lizefan@...wei.com, hannes@...xchg.org, bsingharora@...il.com,
	kamezawa.hiroyu@...fujitsu.com, cgroups@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHSET cgroup/for-3.12] cgroup: make cgroup_event specific to
 memcg

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
SUSE Labs
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