From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [RFC PATCH v8 00/16] Provide a zero-copy method on KVM virtio-net. Date: Fri, 30 Jul 2010 08:02:10 +0300 Message-ID: <4C525CD2.5080604@redhat.com> References: <1280402088-5849-1-git-send-email-xiaohui.xin@intel.com> <1280442682.9058.15.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: xiaohui.xin@intel.com, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com, mingo@elte.hu, davem@davemloft.net, herbert@gondor.hengli.com.au, jdike@linux.intel.com To: Shirley Ma Return-path: In-Reply-To: <1280442682.9058.15.camel@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 07/30/2010 01:31 AM, Shirley Ma wrote: > >> Our goal is to improve the bandwidth and reduce the CPU usage. >> Exact performance data will be provided later. > I did some vhost performance measurement over 10Gb ixgbe, and found that > in order to get consistent BW results, netperf/netserver, qemu, vhost > threads smp affinities are required. > > Looking forward to these results for small message size comparison. For > large message size 10Gb ixgbe BW already reached by doing vhost smp > affinity w/i offloading support, we will see how much CPU utilization it > can be reduced. > > Please provide latency results as well. I did some experimental on > macvtap zero copy sendmsg, what I have found that get_user_pages latency > pretty high. > get_user_pages() is indeed slow. But what about get_user_pages_fast()? Note that when the page is first touched, get_user_pages_fast() falls back to get_user_pages(), so the latency needs to be measured after quite a bit of warm-up. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.