linux-kernel - Re: [PATCH] x86-64 highres/dyntick support

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Date:	Mon, 14 May 2007 08:33:04 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Alistair John Strachan <s0348365@....ed.ac.uk>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	john stultz <johnstul@...ibm.com>, Ingo Molnar <mingo@...e.hu>,
	Chris Wright <chrisw@...s-sol.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] x86-64 highres/dyntick support

Alistair,

On Mon, 2007-05-14 at 02:17 +0100, Alistair John Strachan wrote:
> I've noticed a few problems with this patch series, which I manually (without 
> difficulty) ported to 2.6.22-rc1.

There are a couple of fixups pending. I'm going to push out a new queue
today.

> Only 195 timer interrupts? I only see this on an AMD Opteron, it doesn't occur 
> on an Intel Core 2 Duo. Mainline reports this counter regularly increasing 
> with or without the acpi_pm clocksource loaded.

We stop the PIT when we switch to the local APICs. On your Intel box you
might have deeper C-states which switch the system back to broadcast
mode via PIT.

> Secondly, /proc/cpuinfo seems to be broken:
> 
> alistair@...ocles:~$ cat /proc/cpuinfo | grep MHz
> cpu MHz         : 210779.550
> cpu MHz         : 210779.550
> 
> Unless my CPU is just under 80 times faster than it used to be, these numbers 
> are incorrect. I expect 2700.50, or something similar. cpufreq isn't compiled 
> in.

Hmm. It seems the new TSC calibration routine is hosed.

> Finally, and possibly related, the dmesg timestamps seem to be totally broken. 
> Apparently my machine booted in less than 1 second, with the last messages 
> as:
> 
> [    0.607862] bridge: topology change detected, propagating
> [    0.607862] bridge: port 2(lan-sky) entering forwarding state
> [    0.830472] Linux agpgart interface v0.102 (c) Dave Jones

Hey, you have a really fast box :)

	tglx


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