linux-kernel - Re: [PATCH] x86: c1e_idle: don't mark TSC unstable if CPU has invariant TSC

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Message-ID: <alpine.LFD.1.10.0809191119250.3650@apollo.tec.linutronix.de>
Date:	Fri, 19 Sep 2008 11:21:19 -0700 (PDT)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andreas Herrmann <andreas.herrmann3@....com>
cc:	Valdis.Kletnieks@...edu, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: c1e_idle: don't mark TSC unstable if CPU has
 invariant TSC

On Fri, 19 Sep 2008, Andreas Herrmann wrote:
> TSC on K8 is not P-state and C-state invariant.
> Thus on K8 you'll have a TSC drift if C1E is entered.
> 
> This means that if C1E is enabled TSC should be marked unstable on
> those CPUs (it shouldn't be used as a clocksource).

Correct. I missed that detail with the newer CPUs when I did the C1E
idle stuff. Thanks for catching it. I'll schedule it for Linus when
I'm back from Portland.

Thanks,

	tglx
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