From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754340AbXDQNdT (ORCPT ); Tue, 17 Apr 2007 09:33:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754338AbXDQNdT (ORCPT ); Tue, 17 Apr 2007 09:33:19 -0400 Received: from gw.goop.org ([64.81.55.164]:53350 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754013AbXDQNdT (ORCPT ); Tue, 17 Apr 2007 09:33:19 -0400 Message-ID: <4624CC7C.6040107@goop.org> Date: Tue, 17 Apr 2007 09:32:44 -0400 From: Jeremy Fitzhardinge User-Agent: Thunderbird 1.5.0.10 (X11/20070302) MIME-Version: 1.0 To: Zachary Amsden CC: Andrew Morton , Andi Kleen , Rusty Russell , Chris Wright , Hugh Dickins , David Rientjes , Michel Lespinasse , Virtualization Mailing List , Linux Kernel Mailing List Subject: Re: [PATCH 1/4] Pte drop ptep_get_and_clear paravirt op.patch References: <200704120530.l3C5Ubs0022821@zach-dev.vmware.com> In-Reply-To: <200704120530.l3C5Ubs0022821@zach-dev.vmware.com> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Zachary Amsden wrote: > In shadow mode hypervisors, ptep_get_and_clear achieves the desired > purpose of keeping the shadows in sync by issuing a native_get_and_clear, > followed by a call to pte_update, which indicates the PTE has been > modified. > > Direct mode hypervisors (Xen) have no need for this anyway, and will trap > the update using writable pagetables. > Jan Beulich just posted a patch for Xen/linux which specialzes ptep_get_and_clear, which apparently improves kernel-compile performance by 25-30% on some configurations. I think we'll want to keep this. J