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Subject: Re: Clocksource tsc unstable (delta = -8589361717 ns) in current
 git
From: Peter Zijlstra <peterz@infradead.org>
To: Markus Trippelsdorf <markus@trippelsdorf.de>
Cc: Borislav Petkov <bp@amd64.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
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        Andreas Herrmann <andreas.herrmann3@amd.com>
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Date: Tue, 26 Oct 2010 16:38:50 +0200
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On Tue, 2010-10-26 at 15:58 +0200, Markus Trippelsdorf wrote:
> > 
> > This is strange, tsc is actually stable on your F10h revC.
> 
> Yes. constant_tsc is among the CPU flags. 

constant_tsc only means the TSC is not affected by cpu freq changes.

It has zero relevance to cross-cpu sync of the TSC. The clocksource
stuff requires your TSC to be synchronous over all your CPUs.