linux-kernel - Re: System clock runs too fast after 2.6.27 -> 2.6.28.1 upgrade

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Date:	Thu, 22 Jan 2009 12:03:14 -0800
From:	john stultz <johnstul@...ibm.com>
To:	Miklos Vajna <vmiklos@...galware.org>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Gabriel C <nix.or.die@...glemail.com>,
	CSÉCSY László <boobaa@...galware.org>
Subject: Re: System clock runs too fast after 2.6.27 -> 2.6.28.1 upgrade

On Thu, 2009-01-22 at 20:51 +0100, Miklos Vajna wrote:
> On Wed, Jan 21, 2009 at 01:34:06PM -0800, john stultz <johnstul@...ibm.com> wrote:
> > Miklos: Can you try bisecting this down some?
> 
> I did it two times when I finally realised that it depends on the
> config. So currently I have two config files, with "-good" the clock is
> fine, with "-bad" it's too fast.

Could you send the same info I requested before (available_clocksources,
current_clocksource, dmesg) for both good and bad configs? Also make
sure they're on the same kernel version (as the configs are from
slightly different kernel versions).

> Of course the diff contains unrelated changes as well, I'm trying to
> find which one is the problematic one.

Bisecting the config difference is probably the most reliable way, but
you might try some shots in the dark first:

CONFIG_X86_VISWS: If I recall, this is support for SGI workstations that
had different apics then most systems, and might be related.

CONFIG_PARAVIRT_GUEST: I really haven't been paying much attention to
the paravirt bits, but this has some clock related subconfig options
that might be affecting it.

thanks
-john

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