From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758236AbXGHWug (ORCPT ); Sun, 8 Jul 2007 18:50:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756905AbXGHWu0 (ORCPT ); Sun, 8 Jul 2007 18:50:26 -0400 Received: from smtp2.Stanford.EDU ([171.67.20.25]:42353 "EHLO smtp2.stanford.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756127AbXGHWuZ (ORCPT ); Sun, 8 Jul 2007 18:50:25 -0400 Subject: Re: v2.6.21.5-rt19 From: Fernando Lopez-Lezcano To: Ingo Molnar Cc: Rui Nuno Capela , Thomas Gleixner , LKML , RT-Users , Steven Rostedt , "jcaceres@ccrma.Stanford.EDU" , Carsten Emde , nando@ccrma.Stanford.EDU In-Reply-To: <1183934205.11854.11.camel@cmn3.stanford.edu> References: <1183582155.3291.160.camel@chaos> <9609.194.65.103.1.1183731007.squirrel@www.rncbc.org> <1183758545.20747.34.camel@cmn3.stanford.edu> <20070707092401.GB21234@elte.hu> <1183934205.11854.11.camel@cmn3.stanford.edu> Content-Type: text/plain Date: Sun, 08 Jul 2007 15:50:22 -0700 Message-Id: <1183935022.11854.17.camel@cmn3.stanford.edu> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-4.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2007-07-08 at 15:36 -0700, Fernando Lopez-Lezcano wrote: > On Sat, 2007-07-07 at 11:24 +0200, Ingo Molnar wrote: > > * Fernando Lopez-Lezcano wrote: > > > > > Changes since 2.6.21.5-rt18: > > > > > > > > > > - Fixed a nasty and hard to track down slowness / boot problem on SMP > > > > > machines with CONFIG_NOHZ enabled. The problem was caused by the timer > > > > > wheel base lock held during the get_next_timer_interrupt() call in the > > > > > idle path, which eventually led to a bogus PI boosting of the idle task > > > > > and in consequence a stale wrong scheduler selection for the affected idle > > > > > task. > > > > > > > > > > Kudos to Carsten Emde, who patiently and meticulously isolated the > > > > > problem and provided the traces, which allowed to identify the root cause. > > > > > > > > > > Problem solution: Prevent idle task boosting > > > > > > Maybe someone remember me whining about troubles with 2.6.21-rt2..18 > > > > on my Core2 T7200 laptop (fujitsu-siemens amilo i1520). > > > > > > > > Althought I'm still with my fingers crossed, I can tell the good > > > > news are that 2.6.21.5-rt19 (and -rt20) does behave far better now > > > > on the very same box. > > > > > > Yes, it works much better indeed... > > > > > > Ingo: is there a place where I can read about the changes in different > > > rtxx releases? What is new/better/fixed in rt20? (I see scheduler > > > stuff in a diff from rt19 to rt20 but I don't really know what it > > > means). > > > > and rt18 was a -rt-only NOHZ fix, that bug got introduced in rt11 when > > CFS was merged. > > > > i _think_ Rui might have seen two separate problems. Perhaps by the time > > we fixed the first problem (which Rui saw since -rt2) we introduced the > > other one via -rt11 - which then got fixed in -rt19. > > Ahh, CFS is now part of rt, I was obviously not paying attention... I'm > really trying to provide a "stable" rt kernel for audio usage and > including another subsystem into rt is - IMHO - not going to help. > What's the chance of splitting things? > > > btw., we'd love to get more feedback regarding CFS. CFS is a completely > > new scheduler for Linux. > > Then I'd rather have it separate from rt. Please? I would like to provide the least ammount of new functionality that is really necessary in my audio kernels. Audio related requirements include the rt patch but not a new scheduler. > > It has a design centered around keeping > > application latencies down, so it is ultimately real-time friendly, and > > it should also make things work better for desktop-ish and audio-ish > > stuff as well. (even under SCHED_OTHER) > > Maybe this is CFS related? (tail of a thread in the Planet CCRMA mailing > list): > > On Sun, 2007-07-08 at 15:26 -0400, Hector Centeno wrote: > > Ok, so just to confirm, that 2.6.21-0182.rt19.1.fc7.ccrmart works fine > > on my desktop but on my laptop it makes Firefox and Tomboy to crash. > > On the same laptop using 2.6.21-0182.rt17.1.fc7.ccrmart there is no > > problem. It looks to my untrained eye like it is CFS related, I'm attaching the last part of the strace of firefox while it tries to load a flash site. The firefox process is left in an unkillable (not even by -9) state. What else could I provide to debug the problem? (this is in a T61 laptop with the Intel 7700 processor). -- Fernando