From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755856Ab0CDL3q (ORCPT ); Thu, 4 Mar 2010 06:29:46 -0500 Received: from tx2ehsobe001.messaging.microsoft.com ([65.55.88.11]:35611 "EHLO TX2EHSOBE002.bigfish.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755801Ab0CDL3o (ORCPT ); Thu, 4 Mar 2010 06:29:44 -0500 X-SpamScore: -23 X-BigFish: VPS-23(zz146fK1432R98dN936eMzz1202hzzz32i87h6bh2a8h43h61h) X-Spam-TCS-SCL: 0:0 X-FB-DOMAIN-IP-MATCH: fail X-WSS-ID: 0KYR99B-01-4HB-02 X-M-MSG: Date: Thu, 4 Mar 2010 12:29:34 +0100 From: Joerg Roedel To: Alexander Graf CC: Avi Kivity , Marcelo Tosatti , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/18][RFC] Nested Paging support for Nested SVM (aka NPT-Virtualization) Message-ID: <20100304112934.GL31544@amd.com> References: <1267643541-451-1-git-send-email-joerg.roedel@amd.com> <1282BA89-D8EB-499B-BC49-E50CA64E408D@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1282BA89-D8EB-499B-BC49-E50CA64E408D@suse.de> Organization: Advanced Micro Devices =?iso-8859-1?Q?GmbH?= =?iso-8859-1?Q?=2C_Karl-Hammerschmidt-Str=2E_34=2C_85609_Dornach_bei_M=FC?= =?iso-8859-1?Q?nchen=2C_Gesch=E4ftsf=FChrer=3A_Thomas_M=2E_McCoy=2C_Giuli?= =?iso-8859-1?Q?ano_Meroni=2C_Andrew_Bowd=2C_Sitz=3A_Dornach=2C_Gemeinde_A?= =?iso-8859-1?Q?schheim=2C_Landkreis_M=FCnchen=2C_Registergericht_M=FCnche?= =?iso-8859-1?Q?n=2C?= HRB Nr. 43632 User-Agent: Mutt/1.5.20 (2009-06-14) X-OriginalArrivalTime: 04 Mar 2010 11:29:34.0796 (UTC) FILETIME=[F75758C0:01CABB8D] X-Reverse-DNS: unknown Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 04, 2010 at 12:44:48AM +0100, Alexander Graf wrote: > > On 03.03.2010, at 20:12, Joerg Roedel wrote: > > > Hi, > > > > here are the patches that implement nested paging support for nested > > svm. They are somewhat intrusive to the soft-mmu so I post them as RFC > > in the first round to get feedback about the general direction of the > > changes. Nevertheless I am proud to report that with these patches the > > famous kernel-compile benchmark runs only 4% slower in the l2 guest as > > in the l1 guest when l2 is single-processor. With SMP guests the > > situation is very different. The more vcpus the guest has the more is > > the performance drop from l1 to l2. > > Anyway, this post is to get feedback about the overall concept of these > > patches. Please review and give feedback :-) > > Nice job! It's great to see you finally got around to it :-). > > Have you tracked what slows down SMP l2 guests yet? So far I've been > assuming that IPIs just completely kill the performance, but I guess > it shouldn't be that bad, especially now where you have sped up the > #VMEXIT path that much. I have not yet looked deeper into this issue. I also suspect lockholder preemption to be the cause for this. I did the test with a populated nested page table too and the slowdown is still there. But thats all guessing, I need to do some research for the exact reasons. Joerg