linux-kernel - RE: [PATCH 3/6 v4] cpufreq: tolerate inexact values when collecting stats

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Message-ID: <21672683C5A3814BB4DB938EBE482DE426EA988080@IAD2MBX09.mex02.mlsrvr.com>
Date:	Tue, 13 Nov 2012 14:13:38 -0500
From:	Mark Langsdorf <mark.langsdorf@...xeda.com>
To:	Mark Langsdorf <mark.langsdorf@...xeda.com>,
	Borislav Petkov <bp@...en8.de>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	MyungJoo Ham <myungjoo.ham@...il.com>
Subject: RE: [PATCH 3/6 v4] cpufreq: tolerate inexact values when collecting
 stats

From: linux-pm-owner@...r.kernel.org [linux-pm-owner@...r.kernel.org] On Behalf Of Mark Langsdorf [mark.langsdorf@...xeda.com]

> On 11/13/2012 10:24 AM, Borislav Petkov wrote:
>> On Mon, Nov 12, 2012 at 10:35:49AM -0600, Mark Langsdorf wrote:
>>> The function is buried pretty deep in the cpufreq_stat code. It didn't
>>> seem appropriate to make it a function pointer as part of struct
>>> cpufreq_driver.
>>
>> Better yet, add a flag or a bitfield called "minimize_jitter" or similar
>> and set it only on your hardware...
>
> Doing it in two passes has a similar effect: systems that have exact
> frequencies will get caught in the first pass when the values match. But
> adding a flag makes sense.

I went back and looked at implementing this suggestion.

Although cpufreq_driver has a flag field, no part of cpufreq_driver is directly passed to the cpufreq_stat code. Only cpufreq_policy is. It's cleaner to do passes of the while loop than to copy the cpufreq_driver.flag field into cpufreq_policy and then store it again in cpufreq_stats.

--Mark Langsdorf
Calxeda, Inc.--
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