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

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Date:	Fri, 23 Jan 2009 00:57:27 +0100
From:	Miklos Vajna <vmiklos@...galware.org>
To:	john stultz <johnstul@...ibm.com>
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, Jan 22, 2009 at 12:03:14PM -0800, john stultz <johnstul@...ibm.com> wrote:
> > 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).

Good:

$ cat /sys/devices/system/clocksource/clocksource0/available_clocksource
acpi_pm jiffies tsc
$ cat /sys/devices/system/clocksource/clocksource0/current_clocksource
acpi_pm

Bad:

$ cat /sys/devices/system/clocksource/clocksource0/available_clocksource
tsc pit jiffies
$ cat /sys/devices/system/clocksource/clocksource0/current_clocksource
tsc

> 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.

I just did a new build with CONFIG_X86_VISWS and CONFIG_X86_RDC321X
disabled, but I kept CONFIG_PARAVIRT_GUEST enabled and that works fine
as well. So CONFIG_PARAVIRT_GUEST seems to be unrelated.

(I built these on a faster machine, that's why the gcc version differs,
but that does not matter, I hope.)

Thank you both for your help! :)

View attachment "dmesg-good" of type "text/plain" (28685 bytes)

View attachment "dmesg-bad" of type "text/plain" (28566 bytes)

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