Re: massive performance drop after a while when using virtio nics

Yann Dupont
2008-09-08T12:07:21Z

Fabian Deutsch a écrit :
> Hey.
>
> When running a guest in the following setup, I observ a "massive"
> performance decrease after a couple of gigabytes of transfrerred data.
>
> other guests keep running fine (no regressions) and nothing unusual is
> observed on the host.
>
> fedora 8 host, kvm-72 (user and module)
>
> fedora 9 guest, all updates.
> nic 0, vtio:
> subnet a
> samba listening
>
> nic 1, vtio:
> subnet b
> iscsi initiator running
>
> samba shares a mount point, pointing to an iscsi target.
>
>
> now pulling/pushing about 80GB over samba results in a drop from about
> 60/70Mbit to about 1/2Mbit of troughput.
>
> The problem is reproducible.
> The problem is solved after a reboot of the guest. Just restarting
> networking doesn't help.
> Guest's dmesg doesn't say anything about problems. No errors in
> ifconfig.
>
> Has someone observed something similar?
>
>
> Greetings
> - fabian
>
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>
We just saw the very same issue.
guest & host : 2.6.25.3, debian etch 64 bits

KVM 70 on this machine.

As fabian said, rebooting the kernel doesn't help, but rebooting the
whole kvm guest does.

No error messages as far as I can tell. The kvm guest is a clonezilla
server and send lots of data.
It began to crawl after 2/3 weeks of usage.

Greetings,

--
Yann Dupont - Service IRTS, DSI Université de Nantes
Tel : 02.51.12.53.91 - Mail/Jabber : Yann.Dupont@univ-nantes.fr