From mboxrd@z Thu Jan 1 00:00:00 1970 From: Blaisorblade Subject: Re: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear) Date: Thu, 8 Mar 2007 13:39:29 +0100 References: <20070221023656.6306.246.sendpatchset@linux.site> <20070307092821.GB8609@wotan.suse.de> <20070307094420.GL18774@holomorphy.com> In-Reply-To: <20070307094420.GL18774@holomorphy.com> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200703081339.30372.blaisorblade@yahoo.it> Sender: owner-linux-mm@kvack.org Return-Path: To: Bill Irwin Cc: Nick Piggin , Ingo Molnar , Andrew Morton , Linux Memory Management , Linux Kernel , Benjamin Herrenschmidt List-ID: On Wednesday 07 March 2007 10:44, 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 > address spaces (this likely also applies to UML, though they should > really chime in to confirm). We need it for shared file mappings (for tmpfs only). Our scenario is: RAM is implemented through a shared mapped file, kept on tmpfs (except by dumb users); various processes share an fd for this file (it's opened and immediately deleted). We maintain page tables in x86 style, and TLB flush is implemented through mmap()/munmap()/mprotect(). Having a VMA per each 4K is not the intended VMA usage: for instance, the default /proc/sys/vm/max_map_count (64K) is saturated by a UML process with 64K * 4K = 256M of resident memory. > 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. > > > -- wli -- Inform me of my mistakes, so I can add them to my list! Paolo Giarrusso, aka Blaisorblade http://www.user-mode-linux.org/~blaisorblade Chiacchiera con i tuoi amici in tempo reale! http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com -- 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