linux-kernel - Re: BIOS THRM-Throttling and driver timings

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Message-ID: <20061008211821.GA4280@elf.ucw.cz>
Date:	Sun, 8 Oct 2006 23:18:21 +0200
From:	Pavel Machek <pavel@....cz>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Keith Chew <keith.chew@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: BIOS THRM-Throttling and driver timings

Hi!

> > We have a motherboard that has Thermal Throttling in the BIOS (which
> > we cannot disable). This causes the CPU usage to go up and down when
> > the CPU temperature reaches (and stays around) the Throttling
> > temperature point.
> > 
> > What we would like to know is whether this will affect the timings in
> > drivers, eg the wireless drivers we are using. What can we check in
> > drivers' code that will tell us that its operations may be affected
> > the throttling?
> > 
> > In the past few days, we noticed that some of the linux units we
> > deployed freezes after deveral hours of operation, we are now trying
> > to reproduce the problem in our test environment. Some insight on the
> > affect of throttling will help us narrow down the search.

> in general linux should be ok with this happening. However for specific
> cases... you'll need to provide more information; you're not
> mentioning

Really? AFAICT P4 will happily slow down behind our backs, making at
least udelays() with interrupts disabled sleep for too long.

> (also: if you actually HIT throttling, there is something very very
> wrong; you're not supposed to hit that unless the fan is defective, but
> never in "normal" healthy operation. If you do hit it without hardware
> defects then there is most likely a fundamental airflow problem you'll
> want to fix urgently)

At least in toshiba notebook, I was hitting thermal throttling even
through both fans were okay. There are many misdesigned machines out
there, I fear.
								Pavel 

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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