From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: virtio-net: how to prevent receiving big packages? Date: Mon, 04 Nov 2013 12:35:27 +0800 Message-ID: <5277240F.60800@redhat.com> References: <4b97eaf9-34ad-4221-a273-df47d7244c9c@aliyun.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit To: wangsitan , kvm Return-path: Received: from mx1.redhat.com ([209.132.183.28]:21302 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751280Ab3KDEfp (ORCPT ); Sun, 3 Nov 2013 23:35:45 -0500 In-Reply-To: <4b97eaf9-34ad-4221-a273-df47d7244c9c@aliyun.com> Sender: kvm-owner@vger.kernel.org List-ID: On 11/03/2013 04:07 PM, wangsitan wrote: > Hi all, > > A virtual net interface using virtio_net with TSO on may send big TCP packets (up to 64KB). The receiver will get big packets if it's virtio_net, too. But it will get common packets (according to MTU) if the receiver is e1000 (who re-packaged the data?). > > The transfer with big packets is more efficient. But there's something wrong with my "receiver" vm whose net-core has been modified. Strange behaviours came out when it received big packets. > > I will look at problems on the modified kernel later. What I want to do now is turning off the feature "can receive big packets" of virtio_net in the guest vm (just like I'm using e1000). Is there an easy way to disable it? Or should I change some code in guest's virtio_net? You can disable the feature of VIRTIO_NET_F_HOST_TSO4 and VIRTIO_NET_F_HOST_TSO6 by specifying host_tso4=off,guest_tso6=off in qemu command line. > > Thanks a lot. > > -- > Best Regards > Wangsitan > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html