From: Lee Revell <rlrevell@joe-job.com>
To: Andrew Rodland <arodland@entermail.net>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: voluntary-preempt T3 latency spikes with fan speed change
Date: Mon, 11 Oct 2004 17:56:31 -0400 [thread overview]
Message-ID: <1097531790.1453.55.camel@krustophenia.net> (raw)
In-Reply-To: <ckeec5$id4$1@sea.gmane.org>
On Mon, 2004-10-11 at 13:03, Andrew Rodland wrote:
> 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.
>
Many, many people are seeing this problem (weird, often periodic latency
spikes on laptops that go away when ACPI is disabled). This would
explain a lot of weird bug reports. So are most laptops just
incompatible with low latency applications, or are we talking about a
small minority of broken hardware?
Is there any way to tell a priori whether a machine will have this
problem?
Lee
prev parent reply other threads:[~2004-10-11 22:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-09 10:47 voluntary-preempt T3 latency spikes with fan speed change torbenh
2004-10-11 17:03 ` Andrew Rodland
2004-10-11 21:56 ` Lee Revell [this message]
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