From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932469AbXCNS33 (ORCPT ); Wed, 14 Mar 2007 14:29:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932481AbXCNS32 (ORCPT ); Wed, 14 Mar 2007 14:29:28 -0400 Received: from smtp.osdl.org ([65.172.181.24]:49336 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932469AbXCNS31 (ORCPT ); Wed, 14 Mar 2007 14:29:27 -0400 Date: Wed, 14 Mar 2007 11:27:58 -0700 (PDT) From: Linus Torvalds To: Ingo Molnar cc: Andi Kleen , Steven Rostedt , linux-kernel@vger.kernel.org, Andrew Morton , Chris Wright , Rusty Russell , Glauber de Oliveira Costa Subject: Re: [PATCH 00/18] Make common x86 arch area for i386 and x86_64 - Take 2 In-Reply-To: <20070314180933.GA12994@elte.hu> Message-ID: References: <20070314050819.536207642@goodmis.org> <20070314125330.GA13168@elte.hu> <20070314180933.GA12994@elte.hu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 14 Mar 2007, Ingo Molnar wrote: > > then i decided to analyze the patches: currently they move 13452 lines > of code. i386 is 87847 lines of code, x86_64 is 40978 lines of code, a > total of 128825. That means we move about 10% of the code. Not > insignificant but not earth-shattering either. With alot more effort > (and testing) we could realistically go up to maybe 20% - but that's > still a bit low to spread out all the files, isnt it? Well, I'd like it to be 100% _eventually_, and just unify the architectures. We've now done that both for S/390 and POWER, and I think in both cases it's been a clear win. So it's not like this is even a radical idea. The POWER architecture merge was actually done exactly the incremental way, one file or directory at a time, and seemed to work out fine. So while I'd like 100%, I'd be happy to even just get started with the really obvious stuff. And the stuff that we *already* share certainly fall under that "really obvious" label. > So i thought it's a better idea to continue with the current more > finegrained scheme of sharing some files between the architectures by > having arch/x86_64 be the 'main' repository, with i386 inheriting them > back, instead of spreading out the files? That's really illogical, because historially, i386 was the main one, so you'd have to either: - have a really strange mix OR - move files around just to share them. So I'd much rather have just a totally new architecture, and hope that we can migrate more and more to it. Whether we ever get to the POWER situation where only some really odd-ball special cases are still using ppc or not, who knows? It might be, for example, that only the odder i386 cases (ie the "non-PC" subarchitectures - Voyager, Summit, NUMAQ and the like) would stay in i386. There really is almost nothing in i386 that shouldn't be supported on x86-64 too, unless it literally is the actual low-level asm files and vm86 mode support (which in turn is best left as just a config option that would just *depend* on 32-bit, so even that could sanely be represented in a shared tree without any real downside at all). Linus