From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261596AbVADKFz (ORCPT ); Tue, 4 Jan 2005 05:05:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261598AbVADKFz (ORCPT ); Tue, 4 Jan 2005 05:05:55 -0500 Received: from mx2.elte.hu ([157.181.151.9]:26296 "EHLO mx2.elte.hu") by vger.kernel.org with ESMTP id S261596AbVADKFs (ORCPT ); Tue, 4 Jan 2005 05:05:48 -0500 Date: Tue, 4 Jan 2005 11:05:23 +0100 From: Ingo Molnar To: Lee Revell Cc: linux-kernel , Andrew Morton , Con Kolivas , Rui Nuno Capela , Paul Davis Subject: Re: Latency results with 2.6.10 - looks good Message-ID: <20050104100523.GB14787@elte.hu> References: <1104348820.5218.42.camel@krustophenia.net> <1104549524.3803.28.camel@krustophenia.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1104549524.3803.28.camel@krustophenia.net> User-Agent: Mutt/1.4.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Lee Revell wrote: > Followup: other audio users have confirmed that 2.6.10 is the best > release yet latency-wise. It works most of the time at 64 frames > (~1.33ms latency). > > Now, the bad news: there are still enough xruns to make it not quite > good enough for, say, a recording studio; as we all know with realtime > constraints the worst case scenario is important. As expected the RT > kernel beats it by a wide margin. I have attached some numbers, > excerpted from a post by Rui on the JACK list. The JACK test used was > described previously on this list. > > Ingo, what are your plans for pushing more of the RT patch set > upstream? It seems that the soft/hardirq threading and voluntary > preemption (turning the might_sleep checks into preemption points) are > required to further improve the latency of the standard kernel. These > are well tested at this point and also zero cost for users who don't > enable them. I think if these features go upstream before 2.6.11 then > we can say all of the issues Paul raised, in that post months ago that > led to the VP patches, will be put to rest. for 2.6.11 we have dozens of scheduler patches queued in -mm that do half of the work necessary for the rest of -RT. I'll split out more stuff from -RT once the scheduler queue in -mm gets smaller (i.e. once it gets merged upstream), but there's a natural limit to the rate of merging in a given subsystem, if we push things too hard it will deteriorate. also, there's the necessary merging of preempt-bkl patch. It makes little sense to add the more advanced stuff when the BKL is allowed to generate up to ~200 milliseconds latencies. Hardirq and softirq threading would be the next step after that point. Ingo