From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754797Ab2C0QzV (ORCPT ); Tue, 27 Mar 2012 12:55:21 -0400 Received: from smtp.eu.citrix.com ([62.200.22.115]:9209 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753590Ab2C0QzR (ORCPT ); Tue, 27 Mar 2012 12:55:17 -0400 X-IronPort-AV: E=Sophos;i="4.75,327,1330905600"; d="scan'208";a="11583133" Date: Tue, 27 Mar 2012 17:56:16 +0100 From: Stefano Stabellini X-X-Sender: sstabellini@kaball-desktop To: Konrad Rzeszutek Wilk CC: Stefano Stabellini , "linux-kernel@vger.kernel.org" , "xen-devel@lists.xensource.com" Subject: Re: [PATCH 1/2] xen: enter/exit lazy_mmu_mode around m2p_override calls In-Reply-To: <20120327143142.GA31081@phenom.dumpdata.com> Message-ID: References: <1332856364-29995-1-git-send-email-stefano.stabellini@eu.citrix.com> <20120327143142.GA31081@phenom.dumpdata.com> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 27 Mar 2012, Konrad Rzeszutek Wilk wrote: > On Tue, Mar 27, 2012 at 02:52:43PM +0100, Stefano Stabellini wrote: > > This patch is a significant performance improvement for the > > How much? 10%? 90%? I think you are overestimating the meaning of "significant" :) It is about 6% using grant_table and 2% using blkback. > > m2p_override. > > Can you explain what those calls do in the git commit description please? Right, I have been way too concise. Each m2p_add/remove_override call issues a MULTI_grant_table_op and a __flush_tlb_single if kmap_op != NULL. Batching all the calls together is a great performance benefit because it means issuing one hypercall total rather than two hypercall per page. I'll resend with a proper commit message.