From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754128Ab3A2Ash (ORCPT ); Mon, 28 Jan 2013 19:48:37 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51919 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751720Ab3A2Asg (ORCPT ); Mon, 28 Jan 2013 19:48:36 -0500 Date: Mon, 28 Jan 2013 22:07:15 -0200 From: Marcelo Tosatti To: Xiao Guangrong Cc: Avi Kivity , Gleb Natapov , LKML , KVM Subject: Re: [PATCH v2 06/12] KVM: MMU: introduce a static table to map guest access to spte access Message-ID: <20130129000715.GA10814@amt.cnet> References: <50FFB5A1.5090708@linux.vnet.ibm.com> <50FFB658.6040205@linux.vnet.ibm.com> <20130125001550.GB22875@amt.cnet> <5101F207.6040603@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5101F207.6040603@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 25, 2013 at 10:46:31AM +0800, Xiao Guangrong wrote: > On 01/25/2013 08:15 AM, Marcelo Tosatti wrote: > > On Wed, Jan 23, 2013 at 06:07:20PM +0800, Xiao Guangrong wrote: > >> It makes set_spte more clean and reduces branch prediction > >> > >> Signed-off-by: Xiao Guangrong > >> --- > >> arch/x86/kvm/mmu.c | 37 ++++++++++++++++++++++++++----------- > >> 1 files changed, 26 insertions(+), 11 deletions(-) > > > > Don't see set_spte as being a performance problem? > > IMO the current code is quite simple. > > Yes, this is not a performance problem. > > I just dislike this many continuous "if"-s in the function: > > if (xxx) > xxx > if (xxx) > xxx > .... > > Totally, it has 7 "if"-s before this patch. > > Okay, if you think this is unnecessary, i will drop this patch. :) Yes, please (unless you can show set_spte is a performance problem).