From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751601AbXCHMje (ORCPT ); Thu, 8 Mar 2007 07:39:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751626AbXCHMje (ORCPT ); Thu, 8 Mar 2007 07:39:34 -0500 Received: from smtp009.mail.ukl.yahoo.com ([217.12.11.63]:38179 "HELO smtp009.mail.ukl.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751580AbXCHMjd (ORCPT ); Thu, 8 Mar 2007 07:39:33 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.it; h=Received:X-YMail-OSG:From:To:Subject:Date:User-Agent:Cc:References:In-Reply-To:MIME-Version:Content-Disposition:Content-Type:Content-Transfer-Encoding:Message-Id; b=Y8sviRDZWqtm0FsGvs0LrTSIMc6YeqUiCu5lRcCUM+Vsh+pr6AmLz6MypJMB8O9S3bQbiZv2CMiMIEFWu+EIw/xi9p6AHPOjWZIwZG4IQtD7c+gPe5nFGKqOkc18Fq7VZfThZKm9wsdz+Cv4GPkZZh5kHNQU5Obs0f3aCxnxWaI= ; X-YMail-OSG: ajNqPsoVM1kC3ah4N1fggA0UELive_rPByy9EfzrzqSQ1AlMj4lha3z_8awukYKApH5Y6eLrxFzrA98T8P58XSvGuu_Twr5bmDZojYmqoWF4tdmI9EUCfmVoBbRr1Tp3N5u6GaZQcowr From: Blaisorblade To: Bill Irwin Subject: Re: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear) Date: Thu, 8 Mar 2007 13:39:29 +0100 User-Agent: KMail/1.9.5 Cc: Nick Piggin , Ingo Molnar , Andrew Morton , Linux Memory Management , Linux Kernel , Benjamin Herrenschmidt 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: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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