linux-kernel - Re: [patch v5 06/15] sched: log the cpu utilization at rq

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Date:	Wed, 20 Feb 2013 20:39:20 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
CC:	torvalds@...ux-foundation.org, mingo@...hat.com,
	peterz@...radead.org, tglx@...utronix.de,
	akpm@...ux-foundation.org, arjan@...ux.intel.com, bp@...en8.de,
	pjt@...gle.com, namhyung@...nel.org, efault@....de,
	vincent.guittot@...aro.org, gregkh@...uxfoundation.org,
	viresh.kumar@...aro.org, linux-kernel@...r.kernel.org,
	morten.rasmussen@....com
Subject: Re: [patch v5 06/15] sched: log the cpu utilization at rq

On 02/20/2013 08:19 PM, Preeti U Murthy wrote:
> Hi everyone,
> 
> On 02/18/2013 10:37 AM, Alex Shi wrote:
>> The cpu's utilization is to measure how busy is the cpu.
>>         util = cpu_rq(cpu)->avg.runnable_avg_sum
>>                 / cpu_rq(cpu)->avg.runnable_avg_period;
> 
> Why not cfs_rq->runnable_load_avg? I am concerned with what is the right
> metric to use here.

Here we care the utilization of the cpu not the load avg. load avg maybe
quit bigger on a heavy task(with a big load weight), but maybe it just
used 20% of cpu time, while a light task with 100% cpu usage maybe still
has smaller load avg.

For power consideration, above light task with 100% usage need to take a
cpu, while another heavy task can packing into one cpu with other tasks.


> Refer to this discussion:https://lkml.org/lkml/2012/10/29/448
> 
> Regards
> Preeti U Murthy
> 


-- 
Thanks
    Alex
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