Subject: Re: [RFC v1] Tunable sched_mc_power_savings=n
From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: dipankar@in.ibm.com, balbir@linux.vnet.ibm.com,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       Suresh B Siddha <suresh.b.siddha@intel.com>,
       Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>,
       Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Vatsa <vatsa@linux.vnet.ibm.com>, Gautham R Shenoy <ego@in.ibm.com>
In-Reply-To: <48640C04.9020600@firstfloor.org>
References: <20080625191100.GI21892@dirshya.in.ibm.com>
	 <87k5gcqpbm.fsf@basil.nowhere.org> <4863AF57.3040005@linux.vnet.ibm.com>
	 <4863DB29.1020304@firstfloor.org>
	 <20080626185254.GA12416@dirshya.in.ibm.com>
	 <4863F93C.9040102@firstfloor.org> <20080626210025.GB26167@in.ibm.com>
	 <48640C04.9020600@firstfloor.org>
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Date: Thu, 26 Jun 2008 23:43:04 +0200
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On Thu, 2008-06-26 at 23:37 +0200, Andi Kleen wrote:
> Dipankar Sarma wrote:
> 
> > Some workload managers already do that - they provision cpu and memory
> > resources based on request rates and response times. Such software is
> > in a better position to make a decision whether they can live with
> > reduced performance due to power saving mode or not. The point I am
> > making is the the kernel doesn't have any notion of transactional
> > performance 
> 
> The kernel definitely knows about burstiness vs non burstiness at least
> (although it currently has no long term memory for that). Does it need
> more than that for this? Anyways if nice levels were used that is not
> even needed, because it's ok to run niced processes slower.
> 
> And your workload manager could just nice processes. It should probably
> do that anyways to tell ondemand you don't need full frequency.

Except that I want my nice 19 distcc processes to utilize as much cpu as
possible, but just not bother any other stuff I might be doing...


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