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Date: Fri, 17 Aug 2012 19:47:05 +0100
From: Matthew Garrett <mjg59@srcf.ucam.org>
To: Arjan van de Ven <arjan@linux.intel.com>
Cc: preeti <preeti@linux.vnet.ibm.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>, Alex Shi <alex.shi@intel.com>,
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Subject: Re: [discussion]sched: a rough proposal to enable power saving in
 scheduler
Message-ID: <20120817184705.GB13369@srcf.ucam.org>
References: <5028F12C.7080405@intel.com>
 <1345028738.31459.82.camel@twins>
 <502C98E8.20800@linux.vnet.ibm.com>
 <502CFD35.5000801@linux.intel.com>
 <20120817184100.GA13369@srcf.ucam.org>
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On Fri, Aug 17, 2012 at 11:44:03AM -0700, Arjan van de Ven wrote:
> On 8/17/2012 11:41 AM, Matthew Garrett wrote:
> > On Thu, Aug 16, 2012 at 07:01:25AM -0700, Arjan van de Ven wrote:
> >> this is ... a dubiously general statement.
> >>
> >> for good power, at least on Intel cpus, you want to spread. Parallelism is efficient.
> > 
> > Is this really true? In a two-socket system I'd have thought the benefit 
> > of keeping socket 1 in package C3 outweighed the cost of keeping socket 
> > 0 awake for slightly longer.
> 
> not on Intel
> 
> you can't enter package c3 either until every one is down.
> (e.g. memory controller must stay on etc etc)

I thought that was only PC6 - is there any reason why the package cache 
can't be entirely powered down?

-- 
Matthew Garrett | mjg59@srcf.ucam.org
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