From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 7 Mar 2007 11:02:42 +0100 From: Nick Piggin Subject: Re: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear) Message-ID: <20070307100242.GG8609@wotan.suse.de> References: <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> <20070307094947.GE8609@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070307094947.GE8609@wotan.suse.de> Sender: owner-linux-mm@kvack.org Return-Path: To: Bill Irwin , Ingo Molnar , Andrew Morton , Linux Memory Management , Linux Kernel , Benjamin Herrenschmidt , Paolo 'Blaisorblade' Giarrusso List-ID: On Wed, Mar 07, 2007 at 10:49:47AM +0100, Nick Piggin wrote: > 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. Oh, hmm.... if you can truncate these things then you still need to force unmap so you still need i_mmap_nonlinear. But come to think of it, I still don't think nonlinear mappings are too bad as they are ;) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org