From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758027AbXGHWhD (ORCPT ); Sun, 8 Jul 2007 18:37:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755465AbXGHWgx (ORCPT ); Sun, 8 Jul 2007 18:36:53 -0400 Received: from smtp3.Stanford.EDU ([171.67.20.26]:39489 "EHLO smtp3.stanford.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755160AbXGHWgv (ORCPT ); Sun, 8 Jul 2007 18:36:51 -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: <20070707092401.GB21234@elte.hu> 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> Content-Type: text/plain Date: Sun, 08 Jul 2007 15:36:45 -0700 Message-Id: <1183934205.11854.11.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 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. > 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. > > Cheers, > > Hector > > > On 7/7/07, Hector Centeno wrote: > Hi Fernando, > > I do have Flash installed but for me Firefox crashes when > trying to > access gmail (which AFAIK doesn't use Flash, does it?). Right > now > Firefox is frozen and I'm typing this email using Konkeror (in > Gnome). > This is ps' output: > > hector 3595 1.1 2.2 194352 46336 ? D 16:25 > 0:03 > /usr/lib/firefox-2.0.0.4/firefox-bin > > I think the problem is not present in my Desktop but I have to > double > check. In the same laptop using the stock fedora kernel both > Tomboy > and Firefox work fine. My laptop has a centrino duo processor, > 2 gigs > of ram and the Inte GMA950 graphics chip. > > Hector I managed to completely hang firefox (fc7) with flash 9 installed (unkillable even with -9). Does not seem to happen with flash 7. Have not tried yet with gmail and flash uninstalled. I'll try to strace it to see when/why it hangs. -- Fernando > So it would be nice if you could keep an extra eye on any scheduling > artifacts or regressions, and make sure your favorite workload is still > handled by the Linux scheduler in the utmost best way. I'd like to hear > about any sort of "scheduling behavior / interactivity" regression you > might see, relative to the vanilla kernel. Or if you can see no such > problems then a line of "it works as well as the previous scheduler" is > important info to us too. Thanks!