linux-kernel - Re: [patch v5 14/15] sched: power aware load balance

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Date:	Thu, 21 Mar 2013 17:27:11 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
CC:	mingo@...hat.com, peterz@...radead.org, efault@....de,
	torvalds@...ux-foundation.org, tglx@...utronix.de,
	akpm@...ux-foundation.org, arjan@...ux.intel.com, bp@...en8.de,
	pjt@...gle.com, namhyung@...nel.org, vincent.guittot@...aro.org,
	gregkh@...uxfoundation.org, viresh.kumar@...aro.org,
	linux-kernel@...r.kernel.org, morten.rasmussen@....com
Subject: Re: [patch v5 14/15] sched: power aware load balance

On 03/21/2013 04:41 PM, Preeti U Murthy wrote:
>> > 
> Yes, I did find this behaviour on a 2 socket, 8 core machine very
> consistently.
> 
> rq->util cannot go to 0, after it has begun accumulating load right?
> 
> Say a load was running on a runqueue which had its rq->util to be at
> 100%. After the load finishes, the runqueue goes idle. For every
> scheduler tick, its utilisation decays. But can never become 0.
> 
> rq->util = rq->avg.runnable_avg_sum/rq->avg.runnable_avg_period


did you close all of background system services?
In theory the rq->avg.runnable_avg_sum should be zero if there is no
task a bit long, otherwise there are some bugs in kernel. Could you
check the value under /proc/sched_debug?


-- 
Thanks
    Alex
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