linux-kernel - Re: [patch 9/9] Make use of the Master Timer

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Date:	Fri, 2 Feb 2007 08:05:15 +0100
From:	Andi Kleen <ak@...e.de>
To:	Vojtech Pavlik <vojtech@...e.cz>
Cc:	Jiri Bohac <jbohac@...e.cz>, linux-kernel@...r.kernel.org,
	ssouhlal@...ebsd.org, arjan@...radead.org, tglx@...utronix.de,
	johnstul@...ibm.com, zippel@...ux-m68k.org, andrea@...e.de
Subject: Re: [patch 9/9] Make use of the Master Timer


> > Hmm, I wasn't sure. Why is it needed? How outdated can the
> > result of RDTSC / RDTSCP be?
> > 
> > If I do:
> > 	rdtscll(a)
> > 	...
> > 	rdtscll(b)
> > is it guaranteed that (b > a) ?
> 
> On a single CPU this is always guaranteed. Even on AMD.

It's not guaranteed on Intel at least (but happens to work on P4) 

-Andi
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