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Date: Sun, 5 Jun 2005 13:27:32 +0200
From: Andi Kleen <ak@suse.de>
To: john stultz <johnstul@us.ibm.com>
Cc: Andi Kleen <ak@suse.de>, Parag Warudkar <kernel-stuff@comcast.net>,
       Nishanth Aravamudan <nacc@us.ibm.com>,
       lkml <linux-kernel@vger.kernel.org>,
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       benh@kernel.crashing.org
Subject: Re: [PATCH 3/4] new timeofday x86-64 arch specific changes (v. B1)
Message-ID: <20050605112732.GW23831@wotan.suse.de>
References: <060220051827.15835.429F4FA6000DF9D700003DDB220588617200009A9B9CD3040A029D0A05@comcast.net> <200506021905.08274.kernel-stuff@comcast.net> <1117754453.17804.51.camel@cog.beaverton.ibm.com> <200506021950.35014.kernel-stuff@comcast.net> <20050603163010.GR23831@wotan.suse.de> <1117823257.17804.60.camel@cog.beaverton.ibm.com>
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> How about something like this?
> 
> 300 TSC 
> 200 HPET
> 200 CYCLONE
> 100 ACPI
> 050 PIT
> 010 JIFFIES
> 
> Then if the system has TSC issues (unsynced, cpufreq problems, etc), we

The priority is fine, the problem is getting the decisions for when
to fallback right.

It is quite complicated to decide this, see the x86-64 time.c code 
for this.

> can demote the TSC's priority to 50 and it will fall back nicely without
> manual intervention.

-Andi