linux-kernel - Re: [patch 13/19] GTOD: Mark TSC unusable for highres timers

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Date:	Fri, 10 Nov 2006 13:00:38 +0100
From:	Pavel Machek <pavel@....cz>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Andrew Morton <akpm@...l.org>, tglx@...utronix.de,
	Andi Kleen <ak@...e.de>, john stultz <johnstul@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>, Len Brown <lenb@...nel.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Roman Zippel <zippel@...ux-m68k.org>
Subject: Re: [patch 13/19] GTOD: Mark TSC unusable for highres timers

Hi!

> > > > If so, could that function use the PIT/pmtimer/etc for working out 
> > > > if the TSC is bust, rather than directly using jiffies?
> > > 
> > > there's no realiable way to figure out the TSC is bust: some CPUs 
> > > have a slight 'skew' between cores for example. On some systems the 
> > > TSC might skew between sockets. A CPU might break its TSC only once 
> > > some
> > 
> > But we could still do a whitelist?
> 
> we could, but it would have to be almost empty right now :-) Reason: 

Well, if it would contain at least 50% of the UP machines... that
would be reasonably long list for a start.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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