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

[Yann Dupont <Yann.Dupont@univ-nantes.fr>]

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
>
> --
> 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
>
>   
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