Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262415AbUCMA2h (ORCPT ); Fri, 12 Mar 2004 19:28:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262721AbUCMA2h (ORCPT ); Fri, 12 Mar 2004 19:28:37 -0500 Received: from holomorphy.com ([207.189.100.168]:48391 "EHLO holomorphy.com") by vger.kernel.org with ESMTP id S262415AbUCMA2e (ORCPT ); Fri, 12 Mar 2004 19:28:34 -0500 Date: Fri, 12 Mar 2004 16:28:20 -0800 From: William Lee Irwin III To: Linus Torvalds Cc: Andrea Arcangeli , Rik van Riel , Hugh Dickins , Ingo Molnar , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: anon_vma RFC2 Message-ID: <20040313002820.GW655@holomorphy.com> Mail-Followup-To: William Lee Irwin III , Linus Torvalds , Andrea Arcangeli , Rik van Riel , Hugh Dickins , Ingo Molnar , Andrew Morton , linux-kernel@vger.kernel.org References: <20040311135608.GI30940@dualathlon.random> <20040312122127.GQ30940@dualathlon.random> <20040312124638.GR655@holomorphy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.5.1+cvs20040105i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1551 Lines: 29 On Fri, Mar 12, 2004 at 08:17:49AM -0800, Linus Torvalds wrote: > I have to _violently_ agree with Andrea on this one. > The absolute _LAST_ thing we want to have is a "remnant" rmap > infrastructure that only gets very occasional use. That's a GUARANTEED way > to get bugs, and really subtle behaviour. > I think Andrea is 100% right. Either do rmap for everything (like we do > now, modulo IO/mlock), or do it for _nothing_. No half measures with > "most of the time". > Quite frankly, the stuff I've seen suggested sounds absolutely _horrible_. > Special cases are not just a pain to work with, they definitely will cause > bugs. It's not a matter of "if", it's a matter of "when". > So let's make it clear: if we have an object-based reverse mapping, it > should cover all reasonable cases, and in particular, it should NOT have > rare fallbacks to code that thus never gets any real testing. > And if we have per-page rmap like now, it should _always_ be there. > You do have to realize that maintainability is a HELL of a lot more > important than scalability of performance can be. Please keep that in > mind. The sole point I had to make was against a performance/resource scalabilty argument; the soft issues weren't part of that, though they may ultimately be the deciding factor. -- wli - 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/