From mboxrd@z Thu Jan  1 00:00:00 1970
From: Yann Dupont <Yann.Dupont@univ-nantes.fr>
Subject: Re: massive performance drop after a while when using virtio nics
Date: Mon, 08 Sep 2008 14:07:18 +0200
Message-ID: <48C51576.2000806@univ-nantes.fr>
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Cc: kvm@vger.kernel.org,
	Jean-Philippe MENIL <Jean-Philippe.Menil@univ-nantes.fr>
To: Fabian Deutsch <fabian.deutsch@gmx.de>
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=46abian Deutsch a =E9crit :
> Hey.
>
> When running a guest in the following setup, I observ a "massive"
> performance decrease after a couple of gigabytes of transfrerred data=
=2E
>
> other guests keep running fine (no regressions) and nothing unusual i=
s
> 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 abou=
t
> 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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>
>  =20
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=20
whole kvm guest  does.

No error messages as far as I can tell. The kvm guest is a clonezilla=20
server and send lots of data.
It began to crawl after 2/3 weeks of usage.

Greetings,

--=20
Yann Dupont - Service IRTS, DSI Universit=E9 de Nantes
Tel : 02.51.12.53.91 - Mail/Jabber : Yann.Dupont@univ-nantes.fr