Subject: Re: [BUG] cpu controller can't provide fair CPU time for each group
From: Peter Zijlstra <peterz@infradead.org>
To: Chris Friesen <cfriesen@nortel.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>, Miao Xie <miaox@cn.fujitsu.com>,
       Linux-Kernel <linux-kernel@vger.kernel.org>,
       containers <containers@lists.linux-foundation.org>,
       Ingo Molnar <mingo@elte.hu>
In-Reply-To: <4AFB2109.8010708@nortel.com>
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Date: Wed, 11 Nov 2009 21:51:31 +0100
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On Wed, 2009-11-11 at 14:39 -0600, Chris Friesen wrote:
> On 11/11/2009 01:20 AM, Peter Zijlstra wrote:
> > On Wed, 2009-11-11 at 15:21 +0900, Yasunori Goto wrote:
> > 
> >> When users use cpuset/cpu affinity, then they would like to controll cpu affinity.
> >> Not CPU time.
> > 
> > What are people using affinity for? The only use of affinity is to
> > restrict or disable the load-balancer. Don't complain the load-balancer
> > doesn't work when you're taking active steps to hinder its work.
> 
> I have one active user of scheduler groups (using CKRM though, but they
> want to switch to a new kernel using CFS and sched groups in the near
> future).
> 
> They want to run their app on one cpu by itself with as little
> interference as possible.  Pure cpu processing, not even any I/O except
> via shared memory buffers.  Everything else gets done on the other cpu,
> but they want to control how much of the other cpu is assigned to packet
> processing, how much to system maintenance, normal user shell commands, etc.
> 
> This would seem like a case where some sort of cpuset/affinity  and
> sched groups would be expected to play nice together.

Agreed, and I'd like the load-balance partition feature of cpusets and
the cpu task-groups to work well together, except that the current
interface doesn't allow that nicely.


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