Re: Network poblems using virtio and tap.

[Fabian Deutsch <fabian.deutsch@gmx.de>]

Hello.

It seems to be a problem of virtio. Using e1000 again, I don't get into
trouble anymore.

- fabian

Am Montag, den 01.09.2008, 14:42 +0200 schrieb Fabian Deutsch:
> 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