Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932232AbVJaOVp (ORCPT ); Mon, 31 Oct 2005 09:21:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751255AbVJaOVo (ORCPT ); Mon, 31 Oct 2005 09:21:44 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:30414 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1751244AbVJaOVo (ORCPT ); Mon, 31 Oct 2005 09:21:44 -0500 Date: Mon, 31 Oct 2005 15:22:04 +0100 From: Ingo Molnar To: Mark Knecht Cc: lkml , Lee Revell Subject: Re: 2.6.14-rt1 - xruns in a certain circumstance Message-ID: <20051031142204.GA6136@elte.hu> References: <5bdc1c8b0510301828p29ea517ew467a5f6503435314@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5bdc1c8b0510301828p29ea517ew467a5f6503435314@mail.gmail.com> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=AWL autolearn=disabled SpamAssassin version=3.0.4 0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1468 Lines: 31 * Mark Knecht wrote: > What I'm seeing is that when using basic menus, or when watching > videos I get no xruns. However, if I'm in the preview menu I get an > xrun every few minutes. [...] this could be some sort of hardware latency, as Lee suspects. Videocards are known to be pretty agressively holding the system bus, for the last few percentiles of Quake performance ... Also, mainboard chipsets are sometimes not that good at enforcing fairness between DMA agents - possibly starving the CPU itself for lengthly amounts of time. We have seen such incidents before, and latency tracing ought to be able to show this with reasonable certainty. If it's some sort of generic hardware latency then you ought to see weird traces when enabling WAKEUP_TIMING and LATENCY_TRACING in the .config. No need for any other debug options or Jack level hackery at this point - just enable these and do a: echo 0 > /proc/sys/kernel/preempt_max_latency and try to trigger as large latencies as possible via MythTV. (you wont necessarily see a large latency reported by the kernel when you see an xrun. We can trace xruns too, but that needs Jackd changes and is more effort to set up.) Ingo - 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/