From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264542AbUG2Tmw (ORCPT ); Thu, 29 Jul 2004 15:42:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265027AbUG2Tmw (ORCPT ); Thu, 29 Jul 2004 15:42:52 -0400 Received: from mustang.oldcity.dca.net ([216.158.38.3]:34775 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S264542AbUG2Tmr (ORCPT ); Thu, 29 Jul 2004 15:42:47 -0400 Subject: Re: [patch] voluntary-preempt-2.6.8-rc2-L2, preemptable hardirqs From: Lee Revell To: Ingo Molnar Cc: linux-kernel , William Lee Irwin III , Lenar L?hmus , Andrew Morton , Arjan van de Ven In-Reply-To: <20040729180411.GA16323@elte.hu> References: <1090830574.6936.96.camel@mindpipe> <20040726083537.GA24948@elte.hu> <1090832436.6936.105.camel@mindpipe> <20040726124059.GA14005@elte.hu> <20040726204720.GA26561@elte.hu> <20040727162759.GA32548@elte.hu> <1090968457.743.3.camel@mindpipe> <20040728050535.GA14742@elte.hu> <1091051452.791.52.camel@mindpipe> <1091063295.18598.2.camel@mindpipe> <20040729180411.GA16323@elte.hu> Content-Type: text/plain Message-Id: <1091130189.18598.20.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Thu, 29 Jul 2004 15:43:09 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2004-07-29 at 14:04, Ingo Molnar wrote: > * Lee Revell wrote: > > > Here are some more results. I am up to 56 million interrupts and I > > have yet to trigger a latency higher than 46 usecs. It looks like > > this is a hard upper limit. > > nice - what is the average (and minimum?) latency reported by jackd? > I'd say 46 usecs on a 600 MHz box is quite close to what it takes to > handle an interrupt and schedule to the cache-cold jackd task. It should > definitely be well below the latency required for jackd to do its job > reliably. Yes, I am quite impressed with these results. The jitter is about 5-10% of the total available time at the very lowest latency settings. This is an order of magnitude better than 2.4 + ll. It went as high as 50 usecs, but this took about 100 million interrupts. I have not hacked jackd yet to keep track of the average and minimum value, but eyeballing it I would say 7-8 usecs is the minimum and 25-30 the average. The distribution seems very normal. I am going to try making the RTC irq non-redirectable as well, as I got a few 'rtc: lost some interrupts at 1024 Hz' messages, and the RTC is important for MIDI timing. Other than the few outliers I reported earlier, this is very close to being ready for general pro audio use. I did notice that the msync() XRUN can be reliably reproduced by 'apt-get update && apt-get upgrade'. I think I can speak on behalf of all Linux audio users when I say: thanks a million, to all kernel developers. Lee