From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261378AbUDHCAQ (ORCPT ); Wed, 7 Apr 2004 22:00:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261422AbUDHCAP (ORCPT ); Wed, 7 Apr 2004 22:00:15 -0400 Received: from ozlabs.org ([203.10.76.45]:14566 "EHLO ozlabs.org") by vger.kernel.org with ESMTP id S261378AbUDHCAK (ORCPT ); Wed, 7 Apr 2004 22:00:10 -0400 Date: Thu, 8 Apr 2004 11:57:10 +1000 From: David Gibson To: Benjamin Herrenschmidt Cc: Andrew Morton , Linux Kernel list , Anton Blanchard , Paul Mackerras , linuxppc64-dev Subject: Re: RFC: COW for hugepages Message-ID: <20040408015710.GC20320@zax> Mail-Followup-To: David Gibson , Benjamin Herrenschmidt , Andrew Morton , Linux Kernel list , Anton Blanchard , Paul Mackerras , linuxppc64-dev References: <20040407074239.GG18264@zax> <20040407005353.45323dcd.akpm@osdl.org> <1081326594.1382.54.camel@gaston> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1081326594.1382.54.camel@gaston> User-Agent: Mutt/1.5.5.1+cvs20040105i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 07, 2004 at 06:29:54PM +1000, Benjamin Herrenschmidt wrote: > On Wed, 2004-04-07 at 17:53, Andrew Morton wrote: > > David Gibson wrote: > > > > > > Doing the COW for hugepages turns out not to be terribly difficult. > > > Is there any reason not to apply this patch? > > > > Not much, except that it adds stuff to the kernel. > > > > Does anyone actually have a real-world need for the feature? > > Yup, porting some apps to use hugepages, when those apps > rely on fork & cow semantics typically. Also, implicit use of > hugepages (usually via a malloc override library). I also have some experimental patches for putting ELF segments into large pages (for HPC FORTRAN monsters with massive arrays in the BSS). MAP_PRIVATE semantics (and hence COW) are a clear prerequisite for that. -- 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