From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: e1000 PXE breakage bisected down in kvm-userspace Date: Mon, 04 Aug 2008 16:11:06 -0500 Message-ID: <4897706A.8010206@codemonkey.ws> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Charles Duffy Return-path: Received: from an-out-0708.google.com ([209.85.132.251]:3587 "EHLO an-out-0708.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763437AbYHDVLm (ORCPT ); Mon, 4 Aug 2008 17:11:42 -0400 Received: by an-out-0708.google.com with SMTP id d40so356788and.103 for ; Mon, 04 Aug 2008 14:11:41 -0700 (PDT) In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: Charles Duffy wrote: > Per subject. "git bisect run" script (and libvirt xml helper) attached. Does the problem go away if you make the e1000_can_receive() function always return 1? Regards, Anthony Liguori >> 87b5acf6125d205119e3194c02ed6e71715517dc is first bad commit >> commit 87b5acf6125d205119e3194c02ed6e71715517dc >> Author: Anthony Liguori >> Date: Wed May 7 13:09:40 2008 -0500 >> >> kvm: qemu: stop dropping so many RX packets in tap >> Normally, tap always reads packets and simply lets the client >> drop them if it >> cannot receive them. For virtio-net, this results in massive >> packet loss and >> about an 80% performance loss in TCP throughput. >> This patch modifies qemu_send_packet() to only deliver a >> packet to a VLAN >> client if it doesn't have a fd_can_read method or the fd_can_read >> method >> indicates that it can receive packets. We also return a status >> of whether >> any clients were able to receive the packet. >> If no clients were able to receive a packet, we buffer the >> packet until a >> client indicates that it can receive packets again. >> This patch also modifies the tap code to only read from the >> tap fd if at least >> one client on the VLAN is able to receive a packet. >> Finally, this patch changes the tap code to drain all >> possible packets from >> the tap device when the tap fd is readable. >> Signed-off-by: Anthony Liguori >> Signed-off-by: Avi Kivity >> >> :040000 040000 648a4d52612e0ce68167f279d30bd3f4ec0f22f4 >> 85352e7b252abb1247af2f024eab10a3e8ec0084 M qemu