From mboxrd@z Thu Jan  1 00:00:00 1970
From: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
Subject: Re: [RFC] cgroup TODOs
Date: Mon, 17 Sep 2012 12:55:04 +0400
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To: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Serge Hallyn <serge.hallyn-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>, Thomas Graf <tgraf-G/eBtMaohhA@public.gmane.org>, Paul Mackerras <paulus-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>, "Aneesh Kumar K.V" <aneesh.kumar-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>, Arnaldo Carvalho de Melo <acme-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

On 09/14/2012 07:14 PM, Vivek Goyal wrote:
> Those who really need to implement % model, they will have to do heavy
> lifting in user space. I am skeptical that will take off but kernel
> does not prohibit from somebody creating a group, moving all tasks
> there and making sure tasks and groups are not at same level hence
> % becomes more predictable. Just that, that's not the default from
> kernel.
I subscribe to that.

I use a % model for memory / kernel memory (Give kernel 20 % of
userspace memory), but the kernel never knows about it. It only
understand megabytes. Of course this is simpler, because it is all
inside the same cgroup.

But if you want global %'s you need to calculate it from everybody
*anyway*, be it in the kernel or in userspace.