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

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Date:	Wed, 20 Feb 2013 22:36:56 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	torvalds@...ux-foundation.org, mingo@...hat.com,
	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 09:34 PM, Peter Zijlstra wrote:
> On Wed, 2013-02-20 at 17:39 +0530, Preeti U Murthy wrote:
>> Hi,
>>
>>>>  /*
>>>>   * This is the main, per-CPU runqueue data structure.
>>>>   *
>>>> @@ -481,6 +484,7 @@ struct rq {
>>>>  #endif
>>>>  
>>>>  	struct sched_avg avg;
>>>> +	unsigned int util;
>>>>  };
>>>>  
>>>>  static inline int cpu_of(struct rq *rq)
>>>
>>> You don't actually compute the rq utilization, you only compute the
>>> utilization as per the fair class, so if there's significant RT activity
>>> it'll think the cpu is under-utilized, whihc I think will result in the
>>> wrong thing.
>>
>> Correct me if I am wrong,but isn't the current load balancer also
>> disregarding the real time tasks to calculate the domain/group/cpu level
>> load too?
> 
> Nope, the rt utilization affects the cpu_power, thereby correcting the
> weight stuff.

The balance policy use group capacity, that implicated using cpu power,
but seems capacity is a very rough data.
> 
> 


-- 
Thanks
    Alex
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