Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761524AbYHEPjA (ORCPT ); Tue, 5 Aug 2008 11:39:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761384AbYHEPip (ORCPT ); Tue, 5 Aug 2008 11:38:45 -0400 Received: from mail-out.m-online.net ([212.18.0.9]:49838 "EHLO mail-out.m-online.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761281AbYHEPin (ORCPT ); Tue, 5 Aug 2008 11:38:43 -0400 X-Auth-Info: QgylhOFiHLFFuwzbBPRXZ2gaEktQVto0gaSHB1nNzJQ= X-Auth-Info: D4M4+GlHcr/4nEXhtMCYf3iIixw7BxIvN9SbHqUUQtA= X-Auth-Info: D4M4+GlHcr/4nEXhtMCYf3iIixw7BxIvN9SbHqUUQtA= X-Auth-Info: D4M4+GlHcr/4nEXhtMCYf3iIixw7BxIvN9SbHqUUQtA= X-Auth-Info: D4M4+GlHcr/4nEXhtMCYf3iIixw7BxIvN9SbHqUUQtA= X-Auth-Info: D4M4+GlHcr/4nEXhtMCYf3iIixw7BxIvN9SbHqUUQtA= X-Auth-Info: D4M4+GlHcr/4nEXhtMCYf3iIixw7BxIvN9SbHqUUQtA= Message-ID: <48987486.6010100@grandegger.com> Date: Tue, 05 Aug 2008 17:40:54 +0200 From: Wolfgang Grandegger User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: Steven Rostedt , Luotao Fu , LKML , RT , Ingo Molnar , Thomas Gleixner Subject: Re: 2.6.24-rc8-rt1: Strange latencies on mpc5200 powerpc - RCU issue? References: <20080130010716.GB16069@linux.vnet.ibm.com> <47A032E9.4080105@grandegger.com> <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> <20080801210913.GC14851@linux.vnet.ibm.com> In-Reply-To: <20080801210913.GC14851@linux.vnet.ibm.com> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1224 Lines: 30 Paul E. McKenney wrote: > On Wed, Jul 02, 2008 at 01:03:27PM +0200, Wolfgang Grandegger wrote: >> Wolfgang Grandegger wrote: >>> Steven Rostedt wrote: >>> There seems to be something in trace_mark() keeping latency low: >>> http://lxr.linux.no/linux+v2.6.24.4/include/linux/marker.h#L52 >>> I will follow your suggestions. >> I removed all "likely" and "unlikely" macros, but the latencies did not >> improve. Then I added >> >> preempt_disable(); >> preempt_enable(); >> >> at the two locations mentioned above, like trace_mark() does, and disabled >> CONFIG_RCU_TRACE. That helped to keep the latencies low, and it did for >> 2.6.25.8-rt7 as well. As I see it, adding preemption points seem to prevent >> high latencies. > > Interesting. Perhaps a preempt_enable_no_resched() somewhere that > should be preempt_enable()? FYI, Thomas fixed the real problem a week ago and the patch went into 2.6.24.7-rt16. See his mail with the subject "2.6.24.7-rt16". Wolfgang. -- 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/