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

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Message-ID: <5156F103.6000508@intel.com>
Date:	Sat, 30 Mar 2013 22:04:51 +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 03/30/2013 07:25 PM, Preeti U Murthy wrote:
>> > I still give the rq->util weight even the nr_running is 0, because some
>> > transitory tasks may actived on the cpu, but just missed on balancing point.
>> > 
>> > I just wondering that forgetting rq->util when nr_running = 0 is the
>> > real root cause if your finding is just on VM and without fixed VCPU to
>> > CPU pin.
> I find the same situation on a physical machine too. On a 2 socket, 4
> core machine as well. In fact, using trace_printks in the load balancing
> part, I could find that the reason that the load was not getting
> consolidated onto a socket was because the rq->util of a run-queue with
> no processes on it, had not decayed to 0, which is why it would consider
> the socket as overloaded and would  rule out power aware balancing.All
> this was on a physical machine.

Consider of this situation, we may stop account the rq->util when
nr_running is zero. Tasks will be a bit more compact. but anyway, that's
powersaving policy.

-- 
Thanks
    Alex
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