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Date: Thu, 21 Feb 2013 15:04:26 -0800
From: Anton Vorontsov <anton@enomsg.org>
To: Tejun Heo <tj@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>, cgroups@vger.kernel.org,
        David Rientjes <rientjes@google.com>,
        Pekka Enberg <penberg@kernel.org>, Mel Gorman <mgorman@suse.de>,
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        Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
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        Andrew Morton <akpm@linux-foundation.org>,
        Greg Thelen <gthelen@google.com>,
        Leonid Moiseichuk <leonid.moiseichuk@nokia.com>,
        KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
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Subject: Re: [PATCH v2] memcg: Add memory.pressure_level events
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On Tue, Feb 19, 2013 at 04:21:28PM -0800, Tejun Heo wrote:
> On Tue, Feb 19, 2013 at 4:17 PM, Minchan Kim <minchan@kernel.org> wrote:
> > Should we really enable memcg for just pressure notificaion in embedded side?
> > I didn't check the size(cgroup + memcg) and performance penalty but I don't want
> > to add unnecessary overhead if it is possible.
> > Do you have a plan to support it via global knob(ie, /proc/mempressure), NOT memcg?
> 
> That should be handled by mempressure at the root cgroup. If that adds
> significant amount of overhead code or memory-wise, we just need to
> fix root cgroup handling in memcg. No reason to further complicate the
> interface which already is pretty complex.

For what it worth, I agree here. Even if we decide to make another
interface to vmpressure (which, say, would not require memcg), then it is
better to keep the API the same: eventfd + control file. That way,
API/ABI-wise there will be no differnce between memcg and non-memcg
kernels, which is cool.

Thanks,
Anton