Message-ID: <525C0A51.2080407@linux.intel.com>
Date: Mon, 14 Oct 2013 08:14:25 -0700
From: Arjan van de Ven <arjan@linux.intel.com>
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To: Peter Zijlstra <peterz@infradead.org>
CC: Morten Rasmussen <morten.rasmussen@arm.com>, mingo@kernel.org,
        pjt@google.com, rjw@sisk.pl, dirk.j.brandewie@intel.com,
        vincent.guittot@linaro.org, alex.shi@linaro.org,
        preeti@linux.vnet.ibm.com, efault@gmx.de, corbet@lwn.net,
        tglx@linutronix.de, catalin.marinas@arm.com,
        linux-kernel@vger.kernel.org, linaro-kernel@lists.linaro.org
Subject: Re: [RFC][PATCH 4/7] sched: power: Remove power capacity hints for
 kworker threads
References: <1381511957-29776-1-git-send-email-morten.rasmussen@arm.com> <1381511957-29776-5-git-send-email-morten.rasmussen@arm.com> <20131014133356.GN3081@twins.programming.kicks-ass.net>
In-Reply-To: <20131014133356.GN3081@twins.programming.kicks-ass.net>
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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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