Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752217AbWAEVlb (ORCPT ); Thu, 5 Jan 2006 16:41:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752216AbWAEVlb (ORCPT ); Thu, 5 Jan 2006 16:41:31 -0500 Received: from waste.org ([64.81.244.121]:63180 "EHLO waste.org") by vger.kernel.org with ESMTP id S1751125AbWAEVla (ORCPT ); Thu, 5 Jan 2006 16:41:30 -0500 Date: Thu, 5 Jan 2006 15:34:42 -0600 From: Matt Mackall To: Linus Torvalds Cc: Martin Bligh , Arjan van de Ven , Chuck Ebbert <76306.1226@compuserve.com>, Adrian Bunk , Andrew Morton , Ingo Molnar , linux-kernel , Dave Jones , Tim Schmielau Subject: Re: [patch 00/2] improve .text size on gcc 4.0 and newer compilers Message-ID: <20060105213442.GM3356@waste.org> References: <200601041959_MC3-1-B550-5EE2@compuserve.com> <43BC716A.5080204@mbligh.org> <1136463553.2920.22.camel@laptopd505.fenrus.org> <20060105170255.GK3356@waste.org> <43BD5E6F.1040000@mbligh.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1883 Lines: 38 On Thu, Jan 05, 2006 at 11:40:08AM -0800, Linus Torvalds wrote: > > > On Thu, 5 Jan 2006, Linus Torvalds wrote: > > > > That way the "profile data" actually follows the source code, and is thus > > actually relevant to an open-source project. Because we do _not_ start > > having specially optimized binaries. That's against the whole point of > > being open source and trying to get users to get more deeply involved with > > the project. > > Btw, having annotations obviously works, although it equally obviously > will limit the scope of this kind of profile data. You won't get the same > kind of granularity, and you'd only do the annotations for cases that end > up being very clear-cut. But having an automated feedback cycle for adding > (and removing!) annotations should make it pretty maintainable in the long > run, although the initial annotations migh only end up being for really > core code. > > There's a few papers around that claim that programmers are often very > wrong when they estimate probabilities for different code-paths, and that > you absolutely need automation to get it right. I believe them. But the > fact that you need automation doesn't automatically mean that you should > feed the compiler a profile-data-blob. I think it's a mistake to interleave this data into the C source. It's expensive and tedious to change relative to its volatility. What I was proposing was something like, say, arch/i386/popularity.lst, which would simply contain a list of the most popular n% of functions sorted by popularity. As text, of course. -- Mathematics is the supreme nostalgia of our time. - 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/