Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754768AbZC0GnV (ORCPT ); Fri, 27 Mar 2009 02:43:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751791AbZC0GnJ (ORCPT ); Fri, 27 Mar 2009 02:43:09 -0400 Received: from kuber.nabble.com ([216.139.236.158]:35008 "EHLO kuber.nabble.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751440AbZC0GnI (ORCPT ); Fri, 27 Mar 2009 02:43:08 -0400 Message-ID: <22736728.post@talk.nabble.com> Date: Thu, 26 Mar 2009 23:43:03 -0700 (PDT) From: sidc7 To: linux-kernel@vger.kernel.org Subject: Re: Copy-on-write In-Reply-To: <3e8340490903262235g6174c6b4t4bfd76311be91eeb@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Nabble-From: siddhartha.chhabra@gmail.com References: <22736146.post@talk.nabble.com> <3e8340490903262235g6174c6b4t4bfd76311be91eeb@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1187 Lines: 27 > If the source and destination pages are not in high memory (exactly > where this boundary is depends on your architecture) they do not need > to be mapped before copying. See cow_user_page in mm/memory.c, > copy_user_highpage in include/linux/highmem.h and kmap_atomic in > arch/x86/mm/highmem_32.c (as well as implementations for other > architectures) > Note that on 64-bit platforms, generally there will be no high memory, > and so remappings will never be needed to carry out a COW. Thanks for the quick reply. In general if the kernel wishes to read any arbitrary page mapped to an application's address space, will the kernel cause a page fault on that page, since the page is currently not in its address space and the kernel is wishing to read from this page? Thanks -- View this message in context: http://www.nabble.com/Copy-on-write-tp22736146p22736728.html Sent from the linux-kernel mailing list archive at Nabble.com. -- 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/