Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263967AbUDQMHw (ORCPT ); Sat, 17 Apr 2004 08:07:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263953AbUDQMHv (ORCPT ); Sat, 17 Apr 2004 08:07:51 -0400 Received: from ozlabs.org ([203.10.76.45]:1474 "EHLO ozlabs.org") by vger.kernel.org with ESMTP id S263968AbUDQMHs (ORCPT ); Sat, 17 Apr 2004 08:07:48 -0400 Date: Sat, 17 Apr 2004 22:05:40 +1000 From: "'David Gibson'" To: Ray Bryant Cc: "Chen, Kenneth W" , linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, lse-tech@lists.sourceforge.net, "'Andy Whitcroft'" , "'Andrew Morton'" Subject: Re: hugetlb demand paging patch part [2/3] Message-ID: <20040417120540.GC32444@zax> Mail-Followup-To: 'David Gibson' , Ray Bryant , "Chen, Kenneth W" , linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, lse-tech@lists.sourceforge.net, 'Andy Whitcroft' , 'Andrew Morton' References: <20040416032725.GG12735@zax> <200404160413.i3G4DcF13729@unix-os.sc.intel.com> <20040416044917.GB26707@zax> <40802E69.7040506@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <40802E69.7040506@sgi.com> User-Agent: Mutt/1.5.5.1+cvs20040105i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1980 Lines: 42 On Fri, Apr 16, 2004 at 02:05:13PM -0500, Ray Bryant wrote: > David, > > Is there a big user demand for copy-on-write support for hugetlb pages? > I can understand the rationale for making hugetlb pages behave more like > user pages, and fixing the problem that hugetlb pages are shared across > fork via MAP_SHARE semantics regardless of whether the user requests > MAP_PRIVATE or not, but it just doesn't strike me as something that anyone > who uses hugetlb pages would actually want. My main interest in it is as a prerequisite for various methods of "automatically" using hugepages for programs where it is difficult to manually code them to use hugetlbfs. In particular, think HPC monsters written in FORTRAN. e.g. automatically putting suitable aligned anonymous mmap()s in hugepages under some circumstances (I can't say I like that idea much), using an LD_PRELOAD to put malloc()ated memory into hugepages, or using a hacked ELF loader to put the BSS section (again, think FORTRAN) into hugepages (actually easier and less ugly than it sounds). In any of these cases having the memory have different semantics (MAP_SHARED) to normal anonymous memory would clearly be a Bad Thing. > Of course, YRMV (your requirements may vary). :-) > > 'David Gibson' wrote: > > > >Well, I'm attempting to understand the hugepage code across all the > >archs, so that I can try to implement copy-on-write with a minimum of > >arch specific gunk. Simplifying and consolidating the existing code > >across archs would be a helpful first step, if possible. -- David Gibson | For every complex problem there is a david AT gibson.dropbear.id.au | solution which is simple, neat and | wrong. http://www.ozlabs.org/people/dgibson - 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/