linux-kernel - Re: [RFC PATCH v1 0/3] Saving power by cpu evacuation using sched

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Message-ID: <20090427055451.GF13342@in.ibm.com>
Date:	Mon, 27 Apr 2009 11:24:51 +0530
From:	Dipankar Sarma <dipankar@...ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Suresh B Siddha <suresh.b.siddha@...el.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arjan van de Ven <arjan@...radead.org>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vatsa <vatsa@...ux.vnet.ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>,
	Andi Kleen <andi@...stfloor.org>,
	Gregory Haskins <gregory.haskins@...il.com>,
	Mike Galbraith <efault@....de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arun Bharadwaj <arun@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH v1 0/3] Saving power by cpu evacuation using
	sched_mc=n

On Mon, Apr 27, 2009 at 05:52:16AM +0200, Ingo Molnar wrote:
> 
> Regarding the values for 2...5 - is the AvgPower column time 
> normalized or workload normalized?
> 
> If it's time normalized then it appears there's no power win here at 
> all: we'd be better off by throttling the workload directly (by 
> injecting sleeps or something like that), right?

Energy savings with this will depend on the workload running. We have 
seen transactional workloads where taking off a few cores has almost 
no impact on throughput or response time.

Thanks
Dipankar
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