linux-kernel - Re: [PATCH v5] sched: Avoid unnecessary work in reweight

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Message-ID: <4F4B2105.4080306@linux.vnet.ibm.com>
Date:	Mon, 27 Feb 2012 14:21:57 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5] sched: Avoid unnecessary work in reweight_entity

On 02/27/2012 01:10 PM, Srivatsa Vaddagiri wrote:

> * Michael Wang <wangyun@...ux.vnet.ibm.com> [2012-02-27 13:07:28]:
> 
>>> Is that benchmark run in root (cpu) cgroup? If so, reweight_entity() should not
>>> kick in at all.
>>
>>
>> That's right, if no children group, 'reweight_entity' won't be called, so I have
>> created a cpuset group under root group named 'rg1', and created a memory group
>> under 'rg1' named 'sub', I attached the current shell to the 'sub' cgroup.
> 
> 'cpu' and 'cpuset' cgroup resource controllers are separate. By above
> steps, you would still be running kern-bench in root cgroup as far as cpu
> cgroup controller is concerned ..


I think I really need some study on cgroup first...I've done some totally useless 
test :( , but still confused that why sys time reduced?

And I got a server with Redhat now, so I will do:

1. cgcreate -g cpu:/subcg1
2. echo $$ > /cgroup/cpu/subcg1/tasks
3. open another shell
4. do 1~3 multi times, plan to get 7 cpu cgroup with 7 shell attached to each one.
5. run kernbench in each shell

Please tell me if I missed some thing :)

Regards,
Michael Wang

> 
> - vatsa


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