To: linux-kernel@vger.kernel.org
From: Andrew Rodland <arodland@entermail.net>
Subject: Re: voluntary-preempt T3 latency spikes with fan speed change
Date: Mon, 11 Oct 2004 13:03:01 -0400
Message-ID: <ckeec5$id4$1@sea.gmane.org>
References: <20041009104702.GA14649@mobilat.informatik.uni-bremen.de>
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torbenh@gmx.de wrote:

> 
> hi...
> 
> i am seeing latency spikes (ie jack xruns) when the fan of my
> asus l3d laptop changes speed.
> 
> is there any chance to fix this ?
> i have turned off acpi in the kernel, as this gives me latency spikes
> all over.
> 
> i am quite new to the VP patches, and want to help where i can.
> 
> i also got a quite strange latency trace here:
> 
> could someone sched some light on this please ?
> 

I can't say for certain, but I'm guessing that your laptop has a deeply
broken BIOS that implements ACPI and suchlike by using SMM, which blocks
out interrupts, and there's nothing, I believe, you can do about it.
Disabling ACPI seems sensible; at least you can avoid causing these delays
intentionally, but if some sensor interrupt triggers a flip into SMM to
enable the fan, you're just screwed for a number of milliseconds.

Andrew


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