From: Frans Pop <elendil@planet.nl>
To: Luming Yu <luming.yu@gmail.com>
Subject: Re: [RFC patch] reset TSC at the begining of check_tsc_warp
Date: Tue, 2 Jun 2009 01:10:05 +0200
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Luming Yu wrote:
> Without this patch, we always get kernel warning that TSC warp between
> CPUs, and TSC is marked unstable due to check_tsc_sync_source failed if
> the CPUs have the problem of not-synced initial TSC.
> 
> It hurts CPUs with constant-tsc feature, but with unsynced initial TSC
> value...
> 
> The downside is we could break perfect synced TSC with this patch.
> Please review, test and apply.

I've tested this on my desktop (working TSC) and my laptop (non-working TSC).
On both machines the patch didn't make any difference.

Desktop: Intel mainboard, ICH7 chipset, dual core Pentium D 3.20GHz
$ dmesg | grep -i tsc
Fast TSC calibration using PIT
checking TSC synchronization [CPU#0 -> CPU#1]: passed.

Laptop: HP 2510p notebook, ICH8 chipset, Core2 Duo 1.33GHz
$ dmesg | grep -i tsc
Fast TSC calibration using PIT
checking TSC synchronization [CPU#0 -> CPU#1]: passed.
Marking TSC unstable due to TSC halts in idle
Clocksource tsc unstable (delta = -98164364 ns)

Tested on top of today's mainline git.

Cheers,
FJP
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