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

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Message-ID: <alpine.DEB.1.10.0905071619290.14051@qirst.com>
Date:	Thu, 7 May 2009 16:21:45 -0400 (EDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Alok Kataria <akataria@...are.com>,
	"H. Peter Anvin" <hpa@...or.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

On Thu, 7 May 2009, Alan Cox wrote:

> Given HZ=1 doesn't work, its fairly clear that all you are doing is
> frobbing pointlessly with defaults that have been evolved over about 15
> years because they work.

Are you sure that 1000 HZ default was not developed due to the need to
have sufficient time granulaity for poll and select? In most of the 15
years we did not have high resolution timers.

> Whereas if you make jiffies jiffies() and it reads a timer it puts the
> pain in the right place and you can begin to make actual progress to
> making things work properly.

Good idea. A patch would be appreciated.


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