From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422694AbXCGJtt (ORCPT ); Wed, 7 Mar 2007 04:49:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422696AbXCGJtt (ORCPT ); Wed, 7 Mar 2007 04:49:49 -0500 Received: from cantor2.suse.de ([195.135.220.15]:41318 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422694AbXCGJts (ORCPT ); Wed, 7 Mar 2007 04:49:48 -0500 Date: Wed, 7 Mar 2007 10:49:47 +0100 From: Nick Piggin To: Bill Irwin , Ingo Molnar , Andrew Morton , Linux Memory Management , Linux Kernel , Benjamin Herrenschmidt , "Paolo 'Blaisorblade' Giarrusso" Subject: Re: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear) Message-ID: <20070307094947.GE8609@wotan.suse.de> References: <20070221023656.6306.246.sendpatchset@linux.site> <20070221023735.6306.83373.sendpatchset@linux.site> <20070306225101.f393632c.akpm@linux-foundation.org> <20070307070853.GB15877@wotan.suse.de> <20070307081948.GA9563@wotan.suse.de> <20070307082755.GA25733@elte.hu> <20070307003520.08b1a082.akpm@linux-foundation.org> <20070307085323.GB27337@elte.hu> <20070307092821.GB8609@wotan.suse.de> <20070307094420.GL18774@holomorphy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070307094420.GL18774@holomorphy.com> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 07, 2007 at 01:44:20AM -0800, Bill Irwin wrote: > On Wed, Mar 07, 2007 at 10:28:21AM +0100, Nick Piggin wrote: > > Depending on whether anyone wants it, and what features they want, we > > could emulate the old syscall, and make a new restricted one which is > > much less intrusive. > > For example, if we can operate only on MAP_ANONYMOUS memory and specify > > that nonlinear mappings effectively mlock the pages, then we can get > > rid of all the objrmap and unmap_mapping_range handling, forget about > > the writeout and msync problems... > > Anonymous-only would make it a doorstop for Oracle, since its entire > motive for using it is to window into objects larger than user virtual Uh, duh yes I don't mean MAP_ANONYMOUS, I was just thinking of the shmem inode that sits behind MAP_ANONYMOUS|MAP_SHARED. Of course if you don't have a file descriptor to get a pgoff, then remap_file_pages is a doorstop for everyone ;) > address spaces (this likely also applies to UML, though they should > really chime in to confirm). Restrictions to tmpfs and/or ramfs would > likely be liveable, though I suspect some things might want to do it to > shm segments (I'll ask about that one). There's definitely no need for a > persistent backing store for the object to be remapped in Oracle's case, > in any event. It's largely the in-core destination and source of IO, not > something saved on-disk itself. Yeah, tmpfs/shm segs are what I was thinking about. If UML can live with that as well, then I think it might be a good option.