From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH v2 06/12] KVM: MMU: introduce a static table to map guest access to spte access Date: Fri, 25 Jan 2013 10:46:31 +0800 Message-ID: <5101F207.6040603@linux.vnet.ibm.com> References: <50FFB5A1.5090708@linux.vnet.ibm.com> <50FFB658.6040205@linux.vnet.ibm.com> <20130125001550.GB22875@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Avi Kivity , Gleb Natapov , LKML , KVM To: Marcelo Tosatti Return-path: Received: from e23smtp01.au.ibm.com ([202.81.31.143]:58933 "EHLO e23smtp01.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755269Ab3AYCqm (ORCPT ); Thu, 24 Jan 2013 21:46:42 -0500 Received: from /spool/local by e23smtp01.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 25 Jan 2013 12:41:41 +1000 In-Reply-To: <20130125001550.GB22875@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: 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. :)