Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753467AbYAPR6s (ORCPT ); Wed, 16 Jan 2008 12:58:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751463AbYAPR6l (ORCPT ); Wed, 16 Jan 2008 12:58:41 -0500 Received: from outbound-sin.frontbridge.com ([207.46.51.80]:22403 "EHLO outbound9-sin-R.bigfish.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751418AbYAPR6k (ORCPT ); Wed, 16 Jan 2008 12:58:40 -0500 X-BigFish: VP X-MS-Exchange-Organization-Antispam-Report: OrigIP: 160.33.98.75;Service: EHS Message-ID: <478E467E.6030409@am.sony.com> Date: Wed, 16 Jan 2008 10:01:34 -0800 From: Tim Bird User-Agent: Thunderbird 1.5.0.4 (X11/20060614) MIME-Version: 1.0 To: Steven Rostedt CC: Mathieu Desnoyers , LKML , Ingo Molnar , Linus Torvalds , Andrew Morton , Peter Zijlstra , Christoph Hellwig , Gregory Haskins , Arnaldo Carvalho de Melo , Thomas Gleixner , Sam Ravnborg , "Frank Ch. Eigler" , Steven Rostedt , Paul Mackerras , Daniel Walker Subject: Re: [RFC PATCH 16/22 -v2] add get_monotonic_cycles References: <20080109232914.676624725@goodmis.org> <20080109233044.777564395@goodmis.org> <20080115214636.GD17439@Krystal> <20080115220824.GB22242@Krystal> <20080116031730.GA2164@Krystal> <20080116145604.GB31329@Krystal> <20080116152838.GA970@Krystal> In-Reply-To: X-Enigmail-Version: 0.94.0.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 16 Jan 2008 17:56:29.0491 (UTC) FILETIME=[1EFF3030:01C85869] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1147 Lines: 28 Steven Rostedt wrote: > grmble. Then how do you trace preempt_disable? As my tracer does that > (see the last patch in the series). One way is to make a tracer_preempt_disable() and tracer_preempt_enable(), both of which would be 'notrace'. You could probably optimize them as well. The standard preempt_disable and preempt_enable don't look very efficient (e.g. what's up with converting an increment operation into an addition? - gak!) Any lock you do is going to have a pretty bad effect. In order to be able to trace as much as possible, for KFT, I implemented my own synchronization mechanism using cmpxchg, to avoid using any of the existing kernel locks (which change more often than you'd think, and have weird side effects). ============================= Tim Bird Architecture Group Chair, CE Linux Forum Senior Staff Engineer, Sony Corporation of America ============================= -- 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/