From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756883AbZC2Mr7 (ORCPT ); Sun, 29 Mar 2009 08:47:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756398AbZC2Mri (ORCPT ); Sun, 29 Mar 2009 08:47:38 -0400 Received: from 8bytes.org ([88.198.83.132]:55392 "EHLO 8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756746AbZC2Mrh (ORCPT ); Sun, 29 Mar 2009 08:47:37 -0400 Date: Sun, 29 Mar 2009 14:47:35 +0200 From: Joerg Roedel To: Avi Kivity Cc: Marcelo Tosatti , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/7] Support for GB pages in KVM Message-ID: <20090329124735.GH31080@8bytes.org> References: <1238164319-16092-1-git-send-email-joerg.roedel@amd.com> <20090328214008.GB4694@amt.cnet> <20090328214900.GE31080@8bytes.org> <49CF6390.1020009@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49CF6390.1020009@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 29, 2009 at 03:03:28PM +0300, Avi Kivity wrote: > Joerg Roedel wrote: >> On Sat, Mar 28, 2009 at 06:40:08PM -0300, Marcelo Tosatti wrote: >> >>> On Fri, Mar 27, 2009 at 03:31:52PM +0100, Joerg Roedel wrote: >>> >>>> Hi, >>>> >>>> this patchset extends the KVM MMU implementation to support 1GB pages as >>>> supported by AMD family 16 processors. These patches enable support for >>>> 1 GB pages with Nested Paging. Support for these pages in the shadow >>>> paging code was also developed but does not run stable yet. The patch >>>> for shadow-paging support is not included in this series and will be >>>> sent out seperatly. >>>> >>> Looks generally sane. I'm not sure its even worthwhile to support >>> GBpages with softmmu, because the chance of finding an area without >>> shadowed (write protected) pages is much smaller than with 2MB pages. >>> >> >> Thanks for your review. >> >> The idea behind GB pages in softmmu code was to provide GB pages to the >> guest even if hardware does not support it. This would work better with >> live migration (Only case where we wouldn't have gbpages then would be >> vmx with ept enabled). >> >> >>> Have any numbers to share? >>> >> >> No numbers I fully trust by now. I measured a 32% improvement in >> kernbench using nested pages backed with gb pages. I will do some more >> measurements and share some more solid numbers. >> >> > > Compared to 2M pages? But we're already close to native here. Yes, thats why I don't trust those numbers. I'll find out what went wrong and provide more solid numbers. Joerg