linux-kernel - Re: AMD X2 unsynced TSC fix?

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Date:	Sat, 28 Oct 2006 04:58:27 +0100
From:	Sergio Monteiro Basto <sergio@...giomb.no-ip.org>
To:	Lee Revell <rlrevell@...-job.com>
Cc:	Chris Friesen <cfriesen@...tel.com>, Andi Kleen <ak@...e.de>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	john stultz <johnstul@...ibm.com>
Subject: Re: AMD X2 unsynced TSC fix?

On Fri, 2006-10-27 at 18:08 -0400, Lee Revell wrote: 
> On Fri, 2006-10-27 at 15:48 -0600, Chris Friesen wrote:
> > Lee Revell wrote:
> > 
> > > What exactly does that AMD patch do?
> > 
> > "...by periodically adjusting the core time-stamp-counters, so that they 
> > are synchronized."
> > 
> > It sounds like they just periodically write a new value to the TSC. 
> > Presumably they set the "slower" one equal to the "faster" one.
> > 
> > You'd likely still have windows where time might run backwards, but it 
> > would be better than nothing.
> 
> The patch also apparently changes boot params to make the OS use the
> ACPI PM timer, so it must not be a complete solution.

Hi,
So far, has I can understand. Seems to me that my computer which have a
Pentium D (Dual Core) on VIA chipset, also have unsynchronized TSC and
with the patch of hrtimers on
( http://www.tglx.de/projects/hrtimers/2.6.18/ ) 
Kernel found and use a new clocksource, the acpi_pm. And works stable
but I don't deny that could be a little slower.

Just to point out. This could be more a problem of chipsets than CPUs
(AMD or Intel). AMD just begin first using x86_64 archs :)

Last Note: 
I still have other minor problem, seems (to me) related with SATA
drives. Kernel 2.4.19-rc3 have big changes on SATA and I like to test it
but can't apply hrtimers patch (I don't understand half seems in kernel
other half not). 
In rc3 with jiffies clocksource even with boot parameter "notsc" I have
unsynchronized issues and many "Lost timer tickets", but I can say that
is a regression because computer never work well.

Thanks,
--
Sérgio M. B. 

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