linux-kernel - Re: [patch v8 6/9] sched: compute runnable load avg in cpu_load and cpu_avg_load_per

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Date:	Mon, 10 Jun 2013 10:05:00 +0800
From:	Gu Zheng <guz.fnst@...fujitsu.com>
To:	Alex Shi <alex.shi@...el.com>
CC:	mingo@...hat.com, peterz@...radead.org, tglx@...utronix.de,
	akpm@...ux-foundation.org, bp@...en8.de, pjt@...gle.com,
	namhyung@...nel.org, efault@....de, morten.rasmussen@....com,
	vincent.guittot@...aro.org, preeti@...ux.vnet.ibm.com,
	viresh.kumar@...aro.org, linux-kernel@...r.kernel.org,
	mgorman@...e.de, riel@...hat.com, wangyun@...ux.vnet.ibm.com,
	Jason Low <jason.low2@...com>,
	Changlong Xie <changlongx.xie@...el.com>, sgruszka@...hat.com,
	fweisbec@...il.com
Subject: Re: [patch v8 6/9] sched: compute runnable load avg in cpu_load and
 cpu_avg_load_per_task

On 06/10/2013 10:01 AM, Alex Shi wrote:

> On 06/10/2013 09:49 AM, Gu Zheng wrote:
>> On 06/07/2013 03:20 PM, Alex Shi wrote:
>>
>>>> They are the base values in load balance, update them with rq runnable
>>>> load average, then the load balance will consider runnable load avg
>>>> naturally.
>>>>
>>>> We also try to include the blocked_load_avg as cpu load in balancing,
>>>> but that cause kbuild performance drop 6% on every Intel machine, and
>>>> aim7/oltp drop on some of 4 CPU sockets machines.
>> Hi Alex,
>>    Could you explain me why including the blocked_load_avg causes performance drop ?
> 
> 
> Thanks for review!
> 
> the 9th patch has few explanation. like, after the only task got into
> sleep in a CPU, there is only blocked_load_avg left, it looks quite big
> in short time. that, block it get tasks before sleep, drive task to
> other cpu in periodic balance. So, it cause clear load imbalance.
> 

Got it. Thanks very much for your explanation.:)

Best regards,
Gu
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