From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759263AbZBDV3o (ORCPT ); Wed, 4 Feb 2009 16:29:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753175AbZBDV3f (ORCPT ); Wed, 4 Feb 2009 16:29:35 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:39865 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752776AbZBDV3f (ORCPT ); Wed, 4 Feb 2009 16:29:35 -0500 Date: Wed, 4 Feb 2009 22:29:13 +0100 From: Ingo Molnar To: Andrew Morton Cc: jeremy@goop.org, jaswinderrajput@gmail.com, randy.dunlap@oracle.com, linux-kernel@vger.kernel.org, x86@kernel.org, righi.andrea@gmail.com Subject: Re: mmotm 2009-02-02-17-12 uploaded (x86/nopmd etc.) Message-ID: <20090204212913.GO22608@elte.hu> References: <200902030112.n131CNiq010549@imap1.linux-foundation.org> <498893C8.6080506@oracle.com> <20090203191804.GA24698@elte.hu> <20090203121706.423d5cab.akpm@linux-foundation.org> <20090203212538.GB20527@elte.hu> <20090203134128.37042ea8.akpm@linux-foundation.org> <20090204200846.GF22608@elte.hu> <20090204132529.4b77dd4a.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090204132529.4b77dd4a.akpm@linux-foundation.org> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andrew Morton wrote: > On Wed, 4 Feb 2009 21:08:46 +0100 > Ingo Molnar wrote: > > > > > * Andrew Morton wrote: > > > > > > > This is getting painful. > > > > > > > > the include file spaghetti is ... interesting there, and it's historic. > > > > > > > > I could blame it on highmem, PAE or paravirt - but i'll only blame it on > > > > paravirt for now because those developers are still around! ;-) > > > > > > > > Jeremy, any ideas how to reduce the historic dependency mess in that area? > > > > I think we should go on three routes at once: > > > > > > > > - agressive splitup and separation of type definitions from method > > > > declaration (+ inline definitions). The spinlock_types.h / spinlock.h > > > > splitup was really nice in solving such dependency problems. > > > > > > I like this one. The mixing up of declare-something with use-something > > > is often the source of our woes. > > > > yes. I mapped this problem area once and this is how the include file > > spaghetti gets generated in practice: > > > > - type A gets declared > > - type A gets _used_ in the same file in an inline method, BUT, > > > > that usage also brings in instantiated use of type X1, X2 and X3. > > > > if all types are declared like that everywhere, it can be seen (and it's a > > mathematical certainty) that the only conflict-free way of doing this is to: > > > > - initially add random #include lines to bring in type X1, X2 and X3. > > Which brings in recursive dependencies from those X1 X2 and X3 files. > > > > - when the stuff hits the fan then folks are in a big mess already and > > only a deep restructuring could gets them out of it - which they rarely > > do in an iterative environment. So they work it around iteratively: > > instead of new nice inline methods [which we really prefer] they delay > > all the 'usage' instantiation to .c file via the use of CPP macros > > [which we hate because they hide bugs and cause bugs]. > > None of which would happen if we didn't also have an inlining fetish. inlining is a nice and convenient tool that helps us do better code in many cases. It has this long-term dependency-deteriorating effect though. Ingo