linux-kernel - Re: [RFC][PATCH v5 00/14] sched: packing tasks

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Date:	Mon, 11 Nov 2013 10:20:17 -0800
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, Paul Turner <pjt@...gle.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	Chris Metcalf <cmetcalf@...era.com>,
	Tony Luck <tony.luck@...el.com>,
	"alex.shi@...el.com" <alex.shi@...el.com>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	"len.brown@...el.com" <len.brown@...el.com>,
	"l.majewski@...sung.com" <l.majewski@...sung.com>,
	Jonathan Corbet <corbet@....net>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [RFC][PATCH v5 00/14] sched: packing tasks

On 11/11/2013 10:18 AM, Catalin Marinas wrote:

>
> Even for symmetric configuration, the cost of moving a task to a CPU
> includes wake-up cost plus the run-time cost which depends on the
> P-state after wake-up (that's much trickier since we can't easily
> estimate the cost of a P-state and it may change once you place a task
> on it).

yup including cache refill times (assuming you picked C states
that flushed the cache, which will be the common case... but even
if not, since you're moving at task the likelyhood of cache coldness is high)

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