From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261737AbVGIVYH (ORCPT ); Sat, 9 Jul 2005 17:24:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261736AbVGIVYH (ORCPT ); Sat, 9 Jul 2005 17:24:07 -0400 Received: from amsfep11-int.chello.nl ([213.46.243.19]:32563 "EHLO amsfep19-int.chello.nl") by vger.kernel.org with ESMTP id S261737AbVGIVYE (ORCPT ); Sat, 9 Jul 2005 17:24:04 -0400 Subject: Re: Real-Time Preemption, -RT-2.6.12-final-V0.7.51-12 From: Peter Zijlstra To: William Weston Cc: Ingo Molnar , linux-kernel@vger.kernel.org In-Reply-To: References: <200506301952.22022.annabellesgarden@yahoo.de> <20050630205029.GB1824@elte.hu> <200507010027.33079.annabellesgarden@yahoo.de> <20050701071850.GA18926@elte.hu> <20050703140432.GA19074@elte.hu> <20050703181229.GA32741@elte.hu> <20050707104859.GD22422@elte.hu> <20050708080359.GA32001@elte.hu> Content-Type: text/plain Date: Sat, 09 Jul 2005 23:24:03 +0200 Message-Id: <1120944243.12169.3.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.2.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2005-07-08 at 13:12 -0700, William Weston wrote: > On Fri, 8 Jul 2005, Ingo Molnar wrote: > > > could you check whether the priority leakage happens if you disable SMP? > > (if you can reproduce it easily) > > No priority leakages have been seen with UP configs on any of the > machines I've been testing. > > The leakage is not hard to reproduce under SMT: start up jackd from a > text vc with an rt prio of 60 (or some unique prio above the IRQ threads), > then restart X and login. After several minutes, X and all of its > children will be running at whatever prio jackd was started at (but still > SCHED_NORMAL). Eventually, init, a handful of SCHED_NORMAL kernel > threads, and other random processes are all running at the same priority. > When reset to default priority with chrt or schedtool, these processes > eventually revert back to the leaked priority level. When jackd is > stopped, the priorities stay in their elevated state. If jackd is not > started before logging in to X, then the priority of one of the SCHED_FF > kernel threads is leaked to other processes in the same manner. > I can reproduce priority leakage on my SMP system; any userspace process chrt'ed up and a lot will follow. This makes the system very unresponsive when doing a make -j5. Verified on 51-{6,18,23}. -- Peter Zijlstra