From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Fabian Deutsch" Subject: Network poblems using virtio and tap. Date: Mon, 01 Sep 2008 14:42:45 +0200 Message-ID: <20080901124245.96790@gmx.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kvm@vger.kernel.org Return-path: Received: from mail.gmx.net ([213.165.64.20]:60675 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753191AbYIAMmr (ORCPT ); Mon, 1 Sep 2008 08:42:47 -0400 Sender: kvm-owner@vger.kernel.org List-ID: Hey. I'm observing some network problems when using virtio and a tap if. The trouble is a drop of network troughput from abot 90Mbit/s to about 90kbit/s, after about 1.7 TB of transferred data. Setup Host: - Fedora 8, nearly all updates - Intel(R) Xeon(R) CPU X3210 @ 2.13GHz - 8GB RAM - 2 Guests Guest: - Fedora 9 all updates - virtio nic using tap - samba sharing a mountpoint using an iscsi target Steps to reproduce: 1. Setup a guets using virtio and tap 2. Mount an iscsi target and wokr on the fs or create some traffic on the nic. 2.a I used: # while true ; do sync ; \ time dd if=/dev/zero of=test.bin bs=1M count=1024 ; sync ; time md5sum test.bin ; done 3. Wait a couple of days or about 1.7 TB of data on a 100Mbit/s. Expected results: Everything runs fine, even after 2.5 TB of transferred data or more. Actual results: Everything runs fine up to some point. Then: Troughput drops a bit (from 11 MB/s to about 6MB/s). At some point later the troughput drops to about 90kBit/s. No messages on guest and host. No errors on ifconfig, no dmesg errors. Ping latency increases over time. Logged here: http://www.meinsandkasten.de/log-virtio.pdf Did someone observ something similar or so? Greetings fabian -- Fabian Deutsch