From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759777AbcAUPiq (ORCPT ); Thu, 21 Jan 2016 10:38:46 -0500 Received: from e06smtp15.uk.ibm.com ([195.75.94.111]:34212 "EHLO e06smtp15.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759342AbcAUPim (ORCPT ); Thu, 21 Jan 2016 10:38:42 -0500 X-IBM-Helo: d06dlp01.portsmouth.uk.ibm.com X-IBM-MailFrom: cornelia.huck@de.ibm.com X-IBM-RcptTo: kvm@vger.kernel.org;linux-kernel@vger.kernel.org Date: Thu, 21 Jan 2016 16:38:36 +0100 From: Cornelia Huck To: "Michael S. Tsirkin" Cc: virtio@lists.oasis-open.org, virtio-dev@lists.oasis-open.org, kvm@vger.kernel.org, dev@dpdk.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, "Xie, Huawei" Subject: Re: virtio ring layout changes for optimal single-stream performance Message-ID: <20160121163836.1091943d.cornelia.huck@de.ibm.com> In-Reply-To: <20160121145418-mutt-send-email-mst@redhat.com> References: <20160121145418-mutt-send-email-mst@redhat.com> Organization: IBM Deutschland Research & Development GmbH Vorsitzende des Aufsichtsrats: Martina Koederitz =?UTF-8?B?R2VzY2jDpGZ0c2bDvGhydW5nOg==?= Dirk Wittkopp Sitz der Gesellschaft: =?UTF-8?B?QsO2Ymxpbmdlbg==?= Registergericht: Amtsgericht Stuttgart, HRB 243294 X-Mailer: Claws Mail 3.8.0 (GTK+ 2.24.10; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16012115-0021-0000-0000-00001FE547FE Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 21 Jan 2016 15:39:26 +0200 "Michael S. Tsirkin" wrote: > Hi all! > I have been experimenting with alternative virtio ring layouts, > in order to speed up single stream performance. > > I have just posted a benchmark I wrote for the purpose, and a (partial) > alternative layout implementation. This achieves 20-40% reduction in > virtio overhead in the (default) polling mode. > > http://article.gmane.org/gmane.linux.kernel.virtualization/26889 > > The layout is trying to be as simple as possible, to reduce > the number of cache lines bouncing between CPUs. Some kind of diagram or textual description would really help to review this. > > For benchmarking, the idea is to emulate virtio in user-space, > artificially adding overhead for e.g. signalling to match what happens > in case of a VM. Hm... is this overhead comparable enough between different platform so that you can get a halfway realistic scenario? What about things like endianness conversions? > > I'd be very curious to get feedback on this, in particular, some people > discussed using vectored operations to format virtio ring - would it > conflict with this work? > > You are all welcome to post enhancements or more layout alternatives as > patches. Let me see if I can find time to experiment a bit.