linux-kernel - Re: [PATCH] x86-64: Disable local APIC timer use on AMD systems with C1E

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Date:	Wed, 26 Sep 2007 17:06:51 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>,
	Linus Torvalds <torvalds@...l.org>, Andi Kleen <ak@...e.de>,
	Chuck Ebbert <cebbert@...hat.com>,
	Dave Jones <davej@...hat.com>, Len Brown <lenb@...nel.org>,
	"Langsdorf, Mark" <mark.langsdorf@....com>
Subject: Re: [PATCH] x86-64: Disable local APIC timer use on AMD systems with C1E

On Wednesday, 26 September 2007 10:31, Ingo Molnar wrote:
> 
> * Rafael J. Wysocki <rjw@...k.pl> wrote:
> 
> > On Tuesday, 25 September 2007 22:55, Thomas Gleixner wrote:
> > > On Tue, 2007-09-25 at 22:55 +0200, Rafael J. Wysocki wrote:
> > > > I have reworked the patch a bit so that it applies on top of 2.6.23-rc8-mm1
> > > > and compiles (my version is attached).
> > > > 
> > > > With this patch applied, the kernel boots correctly on the nx6325.
> > > 
> > > I know. It's basically enforced "noapictimer". 
> > > 
> > > But this still does not explain why your nasty box booted current
> > > mainline with "apicmaintimer" on the kernel command line.
> > 
> > Now it doesn't do that any more.
> > 
> > As I wrote in the other thread, I think that _sometimes_ the CPU 
> > doesn't enter the C1E state (or how it's called) and then the box 
> > boots and works.
> 
> Can you see any correlation between being on AC or on battery and this 
> bug occuring?

No.  All tests were done with the AC power supply plugged in.

> Sometimes the BIOS might even do C states depending on  
> whether the box was booted up on AC or on battery. (and sometimes the 
> kernel calibrates things differently when booting up on battery [lower 
> speed] - so this can have an effect too.)

On my box there are hidden history effects related to other things too (eg.
sometimes after a fresh boot the processor generates lots of ACPI events
such that it takes 25% of CPU power to handle them alone).

Greetings,
Rafael
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