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

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Message-ID: <514BB452.2070906@intel.com>
Date:	Fri, 22 Mar 2013 09:30:58 +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 06:27 PM, Preeti U Murthy wrote:
>> > 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 explain why rq->avg.runnable_avg_sum should be zero? What if
> some kernel thread ran on this run queue and is now finished? Its
> utilisation would be say x.How would that ever drop to 0,even if nothing
> ran on it later?

the value get from decay_load():
 sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum,
in decay_load it is possible to be set zero.

and /proc/sched_debug also approve this:

  .tg_runnable_contrib           : 0
  .tg->runnable_avg              : 50
  .avg->runnable_avg_sum         : 0
  .avg->runnable_avg_period      : 47507


-- 
Thanks Alex
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