From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268056AbUHKNeY (ORCPT ); Wed, 11 Aug 2004 09:34:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268059AbUHKNeY (ORCPT ); Wed, 11 Aug 2004 09:34:24 -0400 Received: from mail.gmx.net ([213.165.64.20]:63194 "HELO mail.gmx.net") by vger.kernel.org with SMTP id S268056AbUHKNeU (ORCPT ); Wed, 11 Aug 2004 09:34:20 -0400 X-Authenticated: #4399952 Date: Wed, 11 Aug 2004 15:44:14 +0200 From: Florian Schmidt To: Ingo Molnar Cc: Lee Revell , linux-kernel , Felipe Alfaro Solana Subject: Re: [patch] voluntary-preempt-2.6.8-rc3-O5 Message-Id: <20040811154414.4538027d@mango.fruits.de> In-Reply-To: <20040811124342.GA17017@elte.hu> References: <20040729222657.GA10449@elte.hu> <20040801193043.GA20277@elte.hu> <20040809104649.GA13299@elte.hu> <20040810132654.GA28915@elte.hu> <1092174959.5061.6.camel@mindpipe> <20040811073149.GA4312@elte.hu> <20040811074256.GA5298@elte.hu> <1092210765.1650.3.camel@mindpipe> <20040811090639.GA8354@elte.hu> <20040811141649.447f112f@mango.fruits.de> <20040811124342.GA17017@elte.hu> X-Mailer: Sylpheed-Claws 0.9.12 (GTK+ 1.2.10; i386-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 11 Aug 2004 14:43:42 +0200 Ingo Molnar wrote: > > * Florian Schmidt wrote: > > > > i'm currently running a loop of mlockall-test 100MB on a 466 MHz > > > Celeron, and not a single blip on the radar with a 1000 usecs > > > threshold, after 1 hour of runtime ... > > > > I suppose you're not using jackd. As i have noticed that these > > critical sections only get reported when jackd is running. It seems > > jackd is producing a certain kind of load which exposes them.. > > so you can only trigger the latencies via mlockall-test if jackd is > also running? Yes. I can happily mlockall 500 megs of ram when jackd is not running and i do not get any preempt-timing reports.. As soon as jackd is running even mlockall'ing only 20megs triggers a preempt-timing report and also a alsa xrun report. Hmm, let me try turning off xrun_debug traces while leaving preempt timing reports enabled... Ok, when xrun_debug traces are disabled [but preempt timing is on]. mlocking 20 megs of memory triggers an xrun [now only reported by jackd in it's stdout, not in syslog] but not a preempt timing report. Lee, can you verify? So it seems that the xrun_debug reports from the alsa interface jackd is using triggers the preempt timing reports. So these are really suspicious... So i'm asking myself: How can jackd experience an xrun, when there's no preempt-timing report showing a kernel latency. Jackd is running SCHED_FIFO, so the mlockall_test program should not take away the cpu from jackd. Is mlockall() special in another way? Sorry, i know too little about the kernel internals to ask the right question. Maybe the alsa driver is reacting to the mlockall_test.. Another piece of info which might be valuable (i cannot judge this): I use jackd and mlockall not as root, but as normal user utilizing the realtime lsm which allows non root users to mlock, mlockall and change the scheduling class (via sched_setsched()?). I'll try runnign jackd and the mlockall_test as root to see if the results differ.. > Or do the latencies only trigger in jackd (and related > programs)? Sorry, i don't understand that question.. > > if the later, then i'm wondering whether any of the audio code turns > off caching for specific pages or does DMA to user pages, or mmap()s > device(PCI) memory? Flo -- Palimm Palimm! http://affenbande.org/~tapas/