Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757975AbXEaWHv (ORCPT ); Thu, 31 May 2007 18:07:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752631AbXEaWHo (ORCPT ); Thu, 31 May 2007 18:07:44 -0400 Received: from tomts10.bellnexxia.net ([209.226.175.54]:64005 "EHLO tomts10-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752468AbXEaWHn (ORCPT ); Thu, 31 May 2007 18:07:43 -0400 Date: Thu, 31 May 2007 18:07:42 -0400 From: Mathieu Desnoyers To: Andi Kleen Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [patch 9/9] Scheduler profiling - Use conditional calls Message-ID: <20070531220742.GG904@Krystal> References: <20070530140025.917261793@polymtl.ca> <20070530140229.811672406@polymtl.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 17:56:45 up 3 days, 6:35, 4 users, load average: 0.22, 0.12, 0.14 User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1641 Lines: 52 * Andi Kleen (andi@firstfloor.org) wrote: > Mathieu Desnoyers writes: > > } > > - profile_hit(SCHED_PROFILING, __builtin_return_address(0)); > > + cond_call(profile_on, > > + profile_hit(SCHED_PROFILING, __builtin_return_address(0))); > > Would it be possible to use a syntax like > > if (unlikely_cond_call(variable)) { (or better name) > ... > } > > instead? I think that would be much nicer to read than having > code in a macro argument > I see your point, but there is a level of control on the branch I would lack by doing so: the ability to put the call in either the if or else branch. It is an optimization on i386. I could do it by defining my home-made if() : cond_if (cond_call_name) { code } The macro cond_if could then expand (this is a simplified example) in either in if (cond) or if (cond) else Also, I live in the expectation that, someday, the gcc guys will be nice enough to add some kind of support for a nop-based jump that would require code patching to put a jump instead. If it ever happens, my macro could evolve into this for newer compiler versions, which I could not do with the if() statement you are proposing. -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - 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/