linux-kernel - Re: [PATCH V2 Resend 0/4] Create sched_select_cpu() and use it for workqueues and timers

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Message-ID: <1353951352.6276.43.camel@gandalf.local.home>
Date:	Mon, 26 Nov 2012 12:35:52 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	paulmck@...ux.vnet.ibm.com
Cc:	Viresh Kumar <viresh.kumar@...aro.org>, pjt@...gle.com,
	paul.mckenney@...aro.org, tglx@...utronix.de, tj@...nel.org,
	suresh.b.siddha@...el.com, venki@...gle.com, mingo@...hat.com,
	peterz@...radead.org, Arvind.Chauhan@....com,
	linaro-dev@...ts.linaro.org, patches@...aro.org,
	pdsw-power-team@....com, linux-kernel@...r.kernel.org,
	linux-rt-users@...r.kernel.org
Subject: Re: [PATCH V2 Resend 0/4] Create sched_select_cpu() and use it for
 workqueues and timers

On Mon, 2012-11-26 at 09:03 -0800, Paul E. McKenney wrote:

> If I understand correctly (though also suffering turkey OD), the idea is
> to offload work to more energy-efficient CPUs.

This is determined by a CPU that isn't running the idle task? Is it
because a CPU that just woke up may be running at a lower freq, and thus
not as efficient? But pushing off to another CPU may cause cache misses
as well. Wouldn't that also be a factor in efficiencies, if a CPU is
stalled waiting for memory to be loaded?

I should also ask the obvious. Has these patches shown real world
efficiencies or is this just a theory? Do these patches actually improve
battery life when applied?

Just asking.

-- Steve

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