linux-kernel - Re: PROBLEM: E6850 has an 8+ minute delay during boot

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Date:	Fri, 14 Dec 2007 16:38:58 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Arun Thomas <arun.thomas@...il.com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Jiri Slaby <jirislaby@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: PROBLEM: E6850 has an 8+ minute delay during boot

Arun Thomas wrote:
> On Dec 14, 2007 2:01 PM, H. Peter Anvin <hpa@...or.com> wrote:
>> Thomas Gleixner wrote:
>>> The problem is caused by an SMI during the calibration routine. We
>>> really need to come up with a solid solution which does not rely on
>>> the periodic timer coming in, when there is something else (HPET,
>>> pm_timer) available.
>> How long is the SMI?
> 
> Is there some instrumentation code somewhere which would allow me to
> determine this? If not, can you give me some hints on where to add the
> instrumentation code?

Well, the most obvious way to do it would be to run the calibration loop 
a large number of times, and observe the statistical variation.  In 
particular, one should see a bi- or multimodal pattern where the 
difference between the peaks amount to the "lost time".

When we have a clue about the loss of time then we can figure out how to 
detect it.

	-hpa
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