linux-kernel - Re: [DISCUSSION] removing variety rq->cpu

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Message-ID: <51AD51E3.6060307@linux.vnet.ibm.com>
Date:	Tue, 04 Jun 2013 10:33:07 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Alex Shi <alex.shi@...el.com>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Turner <pjt@...gle.com>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Namhyung Kim <namhyung@...nel.org>,
	Mike Galbraith <efault@....de>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>
Subject: Re: [DISCUSSION] removing variety rq->cpu_load ?

Hi, Alex

On 06/04/2013 09:51 AM, Alex Shi wrote:
> resend with a new subject.

Forgive me but I'm a little lost on this thread...

So we are planing to rely on instant 'cpu_load[0]' and decayed
'runnable_load_avg' only, do we?

Regards,
Michael Wang

> 
>> Peter,
>>
>> I just tried to remove the variety rq.cpu_load, by the following patch. 
>> Because forkexec_idx and busy_idx are all zero, after the patch system just keep cpu_load[0]
>> and remove other values.
>> I tried the patch base 3.10-rc3 and latest tip/sched/core with benchmark dbench,tbench,
>> aim7,hackbench. and oltp of sysbench. Seems performance doesn't change clear.
>> So, for my tested machines, core2, NHM, SNB, with 2 or 4 CPU sockets, and above tested
>> benchmark. We are fine to remove the variety cpu_load. 
>> Don't know if there some other concerns on other scenarios.
>>
>> ---
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 590d535..f0ca983 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -4626,7 +4626,7 @@ static inline void update_sd_lb_stats(struct lb_env *env,
>>         if (child && child->flags & SD_PREFER_SIBLING)
>>                 prefer_sibling = 1;
>>  
>> -       load_idx = get_sd_load_idx(env->sd, env->idle);
>> +       load_idx = 0; //get_sd_load_idx(env->sd, env->idle);
>>  
>>         do {
>>                 int local_group;
>>
>>
> 
> 

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