linux-kernel - Re: Clocksource tsc unstable (delta = -8589361717 ns) in current git

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Message-ID: <1288103930.15336.321.camel@twins>
Date:	Tue, 26 Oct 2010 16:38:50 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Markus Trippelsdorf <markus@...ppelsdorf.de>
Cc:	Borislav Petkov <bp@...64.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"hpa@...ux.intel.com" <hpa@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Andreas Herrmann <andreas.herrmann3@....com>
Subject: Re: Clocksource tsc unstable (delta = -8589361717 ns) in current
 git

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.
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