Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261827AbUCKXna (ORCPT ); Thu, 11 Mar 2004 18:43:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261844AbUCKXn3 (ORCPT ); Thu, 11 Mar 2004 18:43:29 -0500 Received: from bay-bridge.veritas.com ([143.127.3.10]:7901 "EHLO MTVMIME01.enterprise.veritas.com") by vger.kernel.org with ESMTP id S261827AbUCKXn1 (ORCPT ); Thu, 11 Mar 2004 18:43:27 -0500 Date: Thu, 11 Mar 2004 23:43:31 +0000 (GMT) From: Hugh Dickins X-X-Sender: hugh@localhost.localdomain To: Rik van Riel cc: Andrea Arcangeli , Ingo Molnar , Andrew Morton , Linus Torvalds , William Lee Irwin III , Subject: Re: anon_vma RFC2 In-Reply-To: Message-ID: 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 Content-Length: 1703 Lines: 42 On Thu, 11 Mar 2004, Rik van Riel wrote: > On Thu, 11 Mar 2004, Hugh Dickins wrote: > > > length of your essay on vma merging, it strikes me that you've taken > > a wrong direction in switching from my anon mm to your anon vma. > > > > Go by vmas and you have tiresome problems as they are split and merged, > > very commonly. Plus you have the overhead of new data structure per vma. > > There's of course a blindingly simple alternative. > > Add every anonymous page to an "anon_memory" inode. Then > everything is in effect file backed. Using the same page > refcounting we already do, holes get shot into that "file". Okay, Rik, the two extremes belong to you: one anon memory object in total (above), and one per page (your original rmap); whereas Andrea is betting on one per vma, and I go for one per mm. Each way has its merits, I'm sure - and you've placed two bets! > The swap cache code provides a filesystem like mapping > from the anon_memory "files" to the on-disk stuff, or the > anon_memory file pages are resident in memory. For 2.7 something like that may well be reasonable. But let's beware the fancy bloat of extra levels. > As a side effect, it also makes it possible to get rid > of the swapoff code, simply move the anon_memory file > pages from disk into memory... Wonderful if that code could disappear: but I somehow doubt it'll fall out quite so easily - swapoff is inevitably backwards from sanity, isn't it? Hugh - 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/