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Date: Thu, 7 May 2009 18:09:09 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Jeff Garzik <jeff@garzik.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Christoph Lameter <cl@linux.com>,
       Alok Kataria <akataria@vmware.com>, Ingo Molnar <mingo@elte.hu>,
       Thomas Gleixner <tglx@linutronix.de>,
       the arch/x86 maintainers <x86@kernel.org>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86: Reduce the default HZ value
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On Thu, 07 May 2009 12:55:05 -0400
Jeff Garzik <jeff@garzik.org> wrote:

> H. Peter Anvin wrote:
> > Alan Cox wrote:
> >> 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."
> 
> Love to -- now, what will it be replaced with?
> 
> grep for 'deadline' in drivers/ata/libata* to find an example not so 
> easily converted away from jiffies.

I don't see any.

I do see a complicated interface that appears to actually really want to
implement

		add_timer(&foo->expiry_timer);

and checks against the timer completing. In fact it looks as if all the
stuff in there is really down to

		add a timer
		check if it expired
		check how long until it expires
		delete it

And you might as well measure that in HZ=1000's better known as
"milliseconds"