linux-kernel - Re: clocksource change of behavior in 2.6.22 compared to 2.6.20 causes massive system clock slowdown

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Date:	Wed, 11 Jul 2007 01:31:07 +0200
From:	"Alessandro Suardi" <alessandro.suardi@...il.com>
To:	"john stultz" <johnstul@...ibm.com>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Thomas Gleixner" <tglx@...utronix.de>
Subject: Re: clocksource change of behavior in 2.6.22 compared to 2.6.20 causes massive system clock slowdown

On 7/10/07, john stultz <johnstul@...ibm.com> wrote:
> On Tue, 2007-07-10 at 00:29 -0700, Andrew Morton wrote:
> > On Mon, 9 Jul 2007 16:27:59 +0200 "Alessandro Suardi" <alessandro.suardi@...il.com> wrote:
> >
> > > My oldish AMD K7-800's clock began falling behind after
> > >  rebooting from 2.6.20 (and 109 days uptime with a spotless
> > >  clock) into 2.6.22; time lost is about four minutes each hour.
> > >
> > > Turns out that 2.6.22 marks my TSC as unstable and starts
> > >  using PIT instead. Rebooting 2.6.22 with clocksource=tsc
> > >  gets the original stable system time back.
>
> Alessandro,
> Can you send me dmesg output for 2.6.20 and 2.6.22 (without
> clocksource=tsc)?

Actually, I lied a little bit - it was 2.6.22 with clock=tsc (which
 warns on boot about clock= being deprecated in favor of
 clocksource= ). I assume behavior is identical for now.

Please find attached the dmesg ring (incomplete, as the
 kernel ring size I have seems too small to hold the full
 buffer, but it seems to have all the interesting stuff) of
 2.6.20, 2.6.22, 2.6.22 with clock=tsc.

If you need more info, just ask. I'll be out of the country
 from July 12 to the morning of July 16, and again from
 July 17 to July 20, so if you'd rather get at this later on,
 it's okay for me ;)

thanks, ciao,

--alessandro

 "Did you get married but forgot to get divorced ?"

     (Danny and Dusty, 'The Good Old Days')

Download attachment "dmesg-2620" of type "application/octet-stream" (15595 bytes)

Download attachment "dmesg-2622" of type "application/octet-stream" (15601 bytes)

Download attachment "dmesg-2622-clock.tsc" of type "application/octet-stream" (15604 bytes)