linux-kernel - Re: [PATCH 8/7] cpufreq: make the iowait-is-busy-time a sysfs tunable

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Message-ID: <20100504041657.GC13686@1wt.eu>
Date:	Tue, 4 May 2010 06:16:57 +0200
From:	Willy Tarreau <w@....eu>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Thomas Renninger <trenn@...e.de>, Pavel Machek <pavel@....cz>,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	mingo@...e.hu, peterz@...radead.org, tglx@...utronix.de,
	davej@...hat.com, cpufreq@...r.kernel.org, riel@...hat.com
Subject: Re: [PATCH 8/7] cpufreq: make the iowait-is-busy-time a sysfs
 tunable

On Mon, May 03, 2010 at 08:48:18PM -0700, Arjan van de Ven wrote:
> From: Arjan van de Ven <arjan@...ux.intel.com>
> Subject: [PATCH] cpufreq: make the iowait-is-busy-time a sysfs tunable
> 
> Pavel Machek pointed out that not all CPUs have an efficient idle
> at high frequency. Specifically, older Intel and various AMD cpus
> would get a higher power usage when copying files from USB.
> 
> Mike Chan pointed out that the same is true for various ARM chips
> as well.
> 
> Thomas Renninger suggested to make this a sysfs tunable with a
> reasonable default.
> 
> This patch adds a sysfs tunable for the new behavior, and uses
> a very simple function to determine a reasonable default, depending
> on the CPU vendor/type.
> 
> Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>
> ---

That's very nice Arjan. That way we'll be able to select between
performance and power savings, which is what most laptop users
want after all !

Thanks,
Willy

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