linux-kernel - Re: [PATCH] x86,sched: Fix sched_smt_power

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Date:	Tue, 10 Jan 2012 15:41:18 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Youquan Song <youquan.song@...el.com>,
	linux-kernel@...r.kernel.org, tglx@...utronix.de, hpa@...or.com,
	akpm@...ux-foundation.org, stable@...r.kernel.org,
	len.brown@...el.com, anhua.xu@...el.com, chaohong.guo@...el.com,
	Youquan Song <youquan.song@...ux.intel.com>
Subject: Re: [PATCH] x86,sched: Fix sched_smt_power_savings totally broken

On Tue, 2012-01-10 at 06:32 -0800, Arjan van de Ven wrote:
> 
> a very good default would be to keep all tasks on one package until half
> the cores in the package are busy, and then start spreading out. 

Does that still make sense when there's strong NUMA preference? By
forcing stuff on a single package you increase the number of remote
memory fetches (which generally generate more stalls), also the memory
controllers need to stay awake anyway.


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