linux-kernel - Re: [RFC PATCH] x86:Use cpu_khz for loops_per

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Date:	Mon, 23 Jun 2008 22:54:33 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Alok Kataria <akataria@...are.com>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Daniel Hecht <dhecht@...are.com>, Tim Mann <mann@...are.com>,
	Zach Amsden <zach@...are.com>, Sahil Rihan <srihan@...are.com>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [RFC PATCH] x86:Use cpu_khz for loops_per_jiffy calculation


* Alok Kataria <akataria@...are.com> wrote:

> Ok, I have changed the printks to KERN_INFO. 
> 
> On X86 platform we can use the value of tsc_khz computed during tsc 
> calibration to calculate the loops_per_jiffy value. Its very important 
> to keep the error in lpj values to minimum as any error in that may 
> result in kernel panic in check_timer. In virtualization environment, 
> On a highly overloaded host the guest delay calibration may sometimes 
> result in errors beyond the ~50% that timer_irq_works can handle, 
> resulting in the guest panicking.
> 
> Does some formating changes to lpj_setup code to now have a single 
> printk to print the bogomips value.
> 
> We do this only for the boot processor because the AP's can have 
> different base frequencies or the BIOS might boot a AP at a different 
> frequency.

applied to tip/x86/delay - thanks Alok.

could you check whether tip/master (which now includes your changes as 
well) works as expected in your test environment? I had to do a conflict 
resolution in tsc_32.c, i hope i got it right. You can pick it up via:

  http://people.redhat.com/mingo/tip.git/README

	Ingo
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