From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264501AbUGMARg (ORCPT ); Mon, 12 Jul 2004 20:17:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264305AbUGMARg (ORCPT ); Mon, 12 Jul 2004 20:17:36 -0400 Received: from mustang.oldcity.dca.net ([216.158.38.3]:64154 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S264501AbUGMAQ5 (ORCPT ); Mon, 12 Jul 2004 20:16:57 -0400 Subject: Re: [linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch From: Lee Revell To: Andrew Morton Cc: linux-audio-dev@music.columbia.edu, mingo@elte.hu, arjanv@redhat.com, linux-kernel@vger.kernel.org In-Reply-To: <20040712163141.31ef1ad6.akpm@osdl.org> References: <20040709182638.GA11310@elte.hu> <20040710222510.0593f4a4.akpm@osdl.org> <1089673014.10777.42.camel@mindpipe> <20040712163141.31ef1ad6.akpm@osdl.org> Content-Type: text/plain Message-Id: <1089677823.10777.64.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Mon, 12 Jul 2004 20:17:04 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2004-07-12 at 19:31, Andrew Morton wrote: > Lee Revell wrote: > > > > On Sun, 2004-07-11 at 01:25, Andrew Morton wrote: > > > What we need to do is to encourage audio testers to use ALSA drivers, to > > > enable CONFIG_SND_DEBUG in the kernel build and to set > > > /proc/asound/*/*/xrun_debug and to send us the traces which result from > > > underruns. > > > > > > > OK, here goes. The following traces result from running JACK overnight > > like so, on an otherwise idle system. Hardware is a VIA EPIA 6000, with > > a 600Mhz C3 processor. Kernel is 2.6.7 + volunatary_preempt patch. > > voluntary_preempt and kernel_preemption are both on. > > > > jackd -v --realtime -d alsa --outchannels 2 --rate 48000 --shorts > > --playback --period 32 --nperiods 2 > > > > These settings require less than 666 microseconds scheduler latency. > > The average performance is quite good - 5-20 *microseconds*! > > OK, thanks. The problem areas there are the timer-based route cache > flushing and reiserfs. > > We can probably fix the route caceh thing by rescheduling the timer after > having handled 1000 routes or whatever, although I do wonder if this is a > thing we really need to bother about - what else was that machine up to? > Gnutella client. Forgot about that. I agree, it is not reasonable to expect low latency with this kind of network traffic happening. I am impressed it worked as well as it did. > resierfs: yes, it's a problem. I "fixed" it multiple times in 2.4, but the > fixes ended up breaking the fs in subtle ways and I eventually gave up. > Interesting. There is an overwhelming consensus amongst Linux audio folks that you should use reiserfs for low latency work. Should I try ext3? Lee