Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758029AbYGIMyE (ORCPT ); Wed, 9 Jul 2008 08:54:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758696AbYGIMxm (ORCPT ); Wed, 9 Jul 2008 08:53:42 -0400 Received: from metis.extern.pengutronix.de ([83.236.181.26]:39141 "EHLO metis.extern.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755435AbYGIMxk (ORCPT ); Wed, 9 Jul 2008 08:53:40 -0400 Message-ID: <4874B4C0.5090500@pengutronix.de> Date: Wed, 09 Jul 2008 14:53:20 +0200 From: Luotao Fu User-Agent: Mozilla-Thunderbird 2.0.0.12 (X11/20080420) MIME-Version: 1.0 To: Wolfgang Grandegger CC: Steven Rostedt , "Paul E. McKenney" , Luotao Fu , LKML , RT , Ingo Molnar , Thomas Gleixner Subject: Re: 2.6.24-rc8-rt1: Strange latencies on mpc5200 powerpc - RCU issue? References: <20080130102255.GA24890@linux.vnet.ibm.com> <47A0552D.20605@grandegger.com> <20080130105715.GE24890@linux.vnet.ibm.com> <20080130111559.GC20089@pengutronix.de> <486A3EBB.6030905@grandegger.com> <486A573E.60107@grandegger.com> <486B607F.9040903@grandegger.com> <48709348.6000101@grandegger.com> <20080708150826.GA30586@pengutronix.de> <4873C363.3070306@grandegger.com> In-Reply-To: <4873C363.3070306@grandegger.com> X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 10.1.0.86 X-SA-Exim-Mail-From: l.fu@pengutronix.de X-SA-Exim-Scanned: No (on metis.extern.pengutronix.de); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1435 Lines: 37 Hi Wolfgang, Wolfgang Grandegger wrote: > Hi Fun, What's so funny? ;-) [...] > But as Steven pointed out, the preempt_enable_noresched at that place > might be illegal, anyway. In 2.6.25-rt, trace_mark() is no longer > used and I do not see an improvement with CONFIG_RCU_TRAC any more. > Latencies go up to 600us. I also tried with CONFIG_RCU_BOOST > disabled, but it did not improve the latencies. Actually, I still > measure significantly different latencies with 2.6.24.4-rt4, > 2.6.24.7-rt14 and 2.6.25.8-rt7, which is quite frustrating. As you > seem not be able to reproduce my high latencies, I wonder if there > are some toolchain or glibc related issues. I took a quick look into the rcppreempt boost stuff in 2.6.24-rt and 2.6.25-rt. As you have mentioned, trace_mark is no more used in 2.6.24-rt. Instead of that flags are used to detect if the task is preempted. It might indeed probably be some toolchain issue. My powerpc toolchain I'm using here contains gcc 4.1.2 and glibc 2.5 Cheers Fu (without n) -- Dipl.-Ing. Luotao Fu | Phone: +49-5121-206917-3 Pengutronix - Linux Solutions for Science and Industry Entwicklungszentrum Nord http://www.pengutronix.de -- 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/