linux-kernel - Re: [RFC][PATCH 4/7] sched: power: Remove power capacity hints for kworker threads

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Message-ID: <525C0A51.2080407@linux.intel.com>
Date:	Mon, 14 Oct 2013 08:14:25 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Morten Rasmussen <morten.rasmussen@....com>, mingo@...nel.org,
	pjt@...gle.com, rjw@...k.pl, dirk.j.brandewie@...el.com,
	vincent.guittot@...aro.org, alex.shi@...aro.org,
	preeti@...ux.vnet.ibm.com, efault@....de, corbet@....net,
	tglx@...utronix.de, catalin.marinas@....com,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org
Subject: Re: [RFC][PATCH 4/7] sched: power: Remove power capacity hints for
 kworker threads

On 10/14/2013 6:33 AM, Peter Zijlstra wrote:
> On Fri, Oct 11, 2013 at 06:19:14PM +0100, Morten Rasmussen wrote:
>> Removing power hints for kworker threads enables easier use of
>> workqueues in the power driver late callback. That would otherwise
>> lead to an endless loop unless it is prevented in the power driver.
>
> There's many kworker users; some of them actually consume lots of
> cputime. Therefore how did you come to the conclusion that excepting all
> users was the better choice of a little added complexity in the one
> place where it actually matters?

.. and likely only for a very few architectures

x86, and I suspect modern ARM, can change frequency synchronously.
(using an instruction or maybe two or three for ARM)

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