Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755948AbZCELAi (ORCPT ); Thu, 5 Mar 2009 06:00:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753224AbZCELAI (ORCPT ); Thu, 5 Mar 2009 06:00:08 -0500 Received: from ti-out-0910.google.com ([209.85.142.187]:36364 "EHLO ti-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752425AbZCELAC convert rfc822-to-8bit (ORCPT ); Thu, 5 Mar 2009 06:00:02 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=xoqEWWPcCz9amQ1QD2ozdtAnBSn/9+Me5CsLbCj6b6equ5EwuB+LOfPqV1XkrOA3v4 PypTqk3IgvhCrb3i+1dZOInPQte8fZNlLOE3e3bQfpwoDKH/Y8F/bz8f3sFsZ38ny4jk 3FTLBV5xjFCDxfv+cj2sDFvZUK1BozKcbQALU= MIME-Version: 1.0 In-Reply-To: <49AEBB8C.2000405@codemonkey.ws> References: <1235786365-17744-1-git-send-email-jeremy@goop.org> <200902282309.07576.nickpiggin@yahoo.com.au> <49AB19E1.4050604@goop.org> <200903021737.24903.nickpiggin@yahoo.com.au> <49AB9336.7010103@goop.org> <49AEBB8C.2000405@codemonkey.ws> Date: Thu, 5 Mar 2009 10:59:58 +0000 X-Google-Sender-Auth: 728001427f84625d Message-ID: Subject: Re: [Xen-devel] Re: [PATCH] xen: core dom0 support From: George Dunlap To: Anthony Liguori Cc: Jeremy Fitzhardinge , Nick Piggin , Xen-devel , "the arch/x86 maintainers" , Linux Kernel Mailing List , "H. Peter Anvin" , Andrew Morton Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1532 Lines: 32 On Wed, Mar 4, 2009 at 5:34 PM, Anthony Liguori wrote: > Can you point to benchmarks? ?I have a hard time believing this. > > How can shadow paging beat nested paging assuming the presence of large > pages? If these benchmarks would help this discussion, we can certainly run some. As of last Fall, even with superpage support, certain workloads perform significantly less well with HAP (hardware-assisted paging) than with shadow pagetables. Examples are specjbb, which does almost no pagetable updates, but totally thrashes the TLB. SysMark also performed much better with shadow pagetables than HAP. And of course, 64-bit is worse than 32-bit. (It's actually a bit annoying from a default-policy perspective, since about half of our workloads perform better with HAP (up to 30% better) and half of them perform worse (up to 30% worse)). Our comparison would, of course, be comparing Xen+HAP to Xen+Shadow, which isn't necessarily comparable to KVM+HAP. Having HAP work well would be great for us as well as KVM. But there's still the argument about hardware support: Xen can run paravirtualized VMs on hardware with no HVM support, and can run fully virtualized domains very well on hardware that has HVM support but not HAP support. -George Dunlap -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/