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Date: Wed, 22 Aug 2012 06:23:01 -0700 From: Arjan van de Ven <arjan@...ux.intel.com> To: Matthew Garrett <mjg59@...f.ucam.org> CC: Mike Galbraith <efault@....de>, Alan Cox <alan@...rguk.ukuu.org.uk>, Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Alex Shi <alex.shi@...el.com>, Suresh Siddha <suresh.b.siddha@...el.com>, vincent.guittot@...aro.org, svaidy@...ux.vnet.ibm.com, Andrew Morton <akpm@...ux-foundation.org>, Linus Torvalds <torvalds@...ux-foundation.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, Paul Turner <pjt@...gle.com> Subject: Re: [discussion]sched: a rough proposal to enable power saving in scheduler On 8/22/2012 6:21 AM, Matthew Garrett wrote: > On Wed, Aug 22, 2012 at 06:02:48AM -0700, Arjan van de Ven wrote: >> On 8/21/2012 10:41 PM, Mike Galbraith wrote: >>> For my dinky dual core laptop, I suspect you're right, but for a more >>> powerful laptop, I'd expect spread/don't to be noticeable. >> >> yeah if you don't spread, you will waste some power. >> but.. current linux behavior is to spread. >> so we can only make it worse. > > Right. For a single socket system the only thing you can do is use two > threads in preference to using two cores. That'll keep an extra core in > a deep C state for longer, at the cost of keeping the package out of a > deep C state for longer. There might be a win if the two processes > benefit from improved L1 cache locality, or if you're talking about basically "if HT sharing would be good for performance" ;-) (btw this is good news, it means this is not an actual power/performance tradeoff, but a "get it right" tradeoff) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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