From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756043AbYFBLZl (ORCPT ); Mon, 2 Jun 2008 07:25:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751703AbYFBLZd (ORCPT ); Mon, 2 Jun 2008 07:25:33 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:42682 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750986AbYFBLZc (ORCPT ); Mon, 2 Jun 2008 07:25:32 -0400 Date: Mon, 2 Jun 2008 13:25:08 +0200 From: Ingo Molnar To: Jeremy Fitzhardinge Cc: x86@kernel.org, Linux Kernel Mailing List , Jan Beulich , Xen-devel Subject: Re: [PATCH] xen: avoid hypercalls when updating unpinned pud/pmd Message-ID: <20080602112508.GD18586@elte.hu> References: <48409ABB.20301@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <48409ABB.20301@goop.org> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0075] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Jeremy Fitzhardinge wrote: > When operating on an unpinned pagetable (ie, one under construction or > destruction), it isn't necessary to use a hypercall to update a > pud/pmd entry. Jan Beulich observed that a similar optimisation > avoided many thousands of hypercalls while doing a kernel build. > > One tricky part is that early in the kernel boot there's no page > structure, so we can't check to see if the page is pinned. In that > case, we just always use the hypercall. > > Signed-off-by: Jeremy Fitzhardinge > Cc: Jan Beulich applied to tip/x86/xen, thanks Jeremy. Ingo