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Date: Tue, 18 Jun 2002 02:48:23 +0200
From: Kurt Garloff <garloff@suse.de>
To: Benjamin LaHaise <bcrl@redhat.com>
Cc: john stultz <johnstul@us.ibm.com>, marcelo@conectiva.com.br,
       lkml <linux-kernel@vger.kernel.org>,
       "Martin J. Bligh" <Martin.Bligh@us.ibm.com>
Subject: Re: [Patch] tsc-disable_A5
Message-ID: <20020618004823.GB3448@gum01m.etpnet.phys.tue.nl>
Mail-Followup-To: Kurt Garloff <garloff@suse.de>,
	Benjamin LaHaise <bcrl@redhat.com>,
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	lkml <linux-kernel@vger.kernel.org>,
	"Martin J. Bligh" <Martin.Bligh@us.ibm.com>
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Hi Ben,

On Fri, Jun 14, 2002 at 02:53:07PM -0400, Benjamin LaHaise wrote:
> On Fri, Jun 14, 2002 at 11:35:26AM -0700, john stultz wrote:
> > This results in sequential calls to gettimeofday to return
> > non-sequential time values. By disabling the TSCs on these boxes, it
> > forces gettimeofday to use the PIC clock instead, fixing the problem.=
=20
>=20
> This seems to be yet another reason for supporting per-CPU TSC=20
> calibration, as that would fix machines with different speed cpus, too.

I agree.
Maybe the patch I once made to support CPUs with different speeds can serve
as a starting point?

http://www.uwsg.iu.edu/hypermail/linux/kernel/0203.1/0481.html

However, one would need to make sure that all CPUs occasionally do receive
timer interrupts, otherwise your TSC may overflow. Depending on your
hardware (APICs), this might be an issue. I've been told that Fosters do
misbehave ...

Regards,
--=20
Kurt Garloff  <garloff@suse.de>                          Eindhoven, NL
GPG key: See mail header, key servers         Linux kernel development
SuSE Linux AG, Nuernberg, DE                            SCSI, Security

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