Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269291AbUJKWIL (ORCPT ); Mon, 11 Oct 2004 18:08:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269285AbUJKWF4 (ORCPT ); Mon, 11 Oct 2004 18:05:56 -0400 Received: from viper.oldcity.dca.net ([216.158.38.4]:58600 "HELO viper.oldcity.dca.net") by vger.kernel.org with SMTP id S269298AbUJKWFM (ORCPT ); Mon, 11 Oct 2004 18:05:12 -0400 Subject: Re: voluntary-preempt T3 latency spikes with fan speed change From: Lee Revell To: Andrew Rodland Cc: linux-kernel In-Reply-To: References: <20041009104702.GA14649@mobilat.informatik.uni-bremen.de> Content-Type: text/plain Message-Id: <1097531790.1453.55.camel@krustophenia.net> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Mon, 11 Oct 2004 17:56:31 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1601 Lines: 44 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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/