linux-kernel - Re: [RFC v1] Tunable sched_mc_power

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Date:	Fri, 27 Jun 2008 08:54:12 -0400
From:	David Collier-Brown <davecb@....com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Suresh B Siddha <suresh.b.siddha@...el.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vatsa <vatsa@...ux.vnet.ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>
Subject: Re: [RFC v1] Tunable sched_mc_power_savings=n

KOSAKI Motohiro wrote:
> Hi
> 
> 
>>Advantages:
>>
>>* Enterprise workloads on large hardware configurations may need
>>  aggressive consolidation strategy
>>* Performance impact on server is different from desktop or laptops.
>>  Interactivity is less of a concern on large enterprise servers while
>>  workload response times and performance per watt is more significant
>>* Aggressive power savings even with marginal performance penalty is
>>  is a useful tunable for servers since it may provide good
>>  performance-per-watt at low utilisation
>>* This tunable can influence other parts of scheduler like wakeup
>>  biasing for overall task consolidation  
> 
> 
> I'd like to know how many saving power.
> if there are only small saving, I think this is not interesting feature.
> 
> Do you expect how many percentage saving?
> 

An experiment using DVFS on Xeon yeilded a 15-watt allowable reduction
even under running a considerable TPC-W workload.  Lesser loads allowed
a 40-watt (out of 160) reduction.  

--dave
-- 
David Collier-Brown            | Always do right. This will gratify
Sun Microsystems, Toronto      | some people and astonish the rest
davecb@....com                 |                      -- Mark Twain
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