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

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Date:	Wed, 20 Feb 2013 14:34:24 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc:	Alex Shi <alex.shi@...el.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 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.


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