linux-kernel - Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource group and PRIO

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Message-ID: <1460614057.5100.150.camel@gmail.com>
Date:	Thu, 14 Apr 2016 08:07:37 +0200
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Johannes Weiner <hannes@...xchg.org>,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	mingo@...hat.com, lizefan@...wei.com, pjt@...gle.com,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	linux-api@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCHSET RFC cgroup/for-4.6] cgroup, sched: implement resource
 group and PRIO_RGRP

On Wed, 2016-04-13 at 11:59 -0400, Tejun Heo wrote:
> Hello, Mike.
> 
> On Wed, Apr 13, 2016 at 09:43:01AM +0200, Mike Galbraith wrote:
> > > The cost is part aesthetical and part practical.  While less
> > > elegant
> > > than tree of uniform objects, it seems a stretch to call internal
> > > /
> > > leaf node distinction broken especially given that the model is
> > > natural to some controllers.
> > 
> > That justifies prohibiting proper usages of three controllers, cpu,
> > cpuacct and cpuset?
> 
> Neither cpuacct or cpuset loses any capability from the constraint as
> there is no difference between tasks being in an internal cgroup or a
> leaf cgroup nested under it.  The only practical impact is that we
> lose the ability to let internal tasks compete against sibling cgroups
> for proportional control.

I'm not getting it.

A.  entity = task[s] | cgroup[s]
B.  entity = task[s] ^ cgroup[s]

A I get, B I don't, but you seem to be saying B, else we get the task
competes with sibling cgroup business.

Let /foo be an exclusive cpuset containing exclusive subset bar.  How can any task acquire set foo affinity if B really really applies?  My box calls me a dummy if I try to create a "proper" home for tasks, one with both no snobby neighbors and proper affinity.

	-Mike