linux-kernel - Re: [PATCH] x86: Reduce the default HZ value

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Message-ID: <4A02FE91.8070006@zytor.com>
Date:	Thu, 07 May 2009 08:30:25 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Christoph Lameter <cl@...ux.com>,
	Alok Kataria <akataria@...are.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	the arch/x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: Reduce the default HZ value

Alan Cox wrote:
> On Thu, 7 May 2009 10:13:52 -0400 (EDT)
> Christoph Lameter <cl@...ux.com> wrote:
> 
>> I think we need to reduce the general tick frequency to be as low as
>> possible. With high resolution timers the tick frequency is just the
>> frequency with which the timer interrupt disturbs a running application.
>>
>> Are there any benefits remaining from frequent timer interrupts? I would
>> think that 60 HZ would be sufficient.
> 
> 50 works for various european video apps, 60 breaks, 60 works for various
> US video apps, 50 breaks. Now that may have changed with all the select
> stuff being hrtimer based (which I'd missed).

Hence 300 Hz.  ;)

> Hooray - finally someone admits the *real* problem here, and for power
> management too. Otherwise known as "referencing jiffies as a variable must
> die"

Amen.  Also, "using HZ as a unit of measurement must die, too."

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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