Re: more UDP packet loss?

[Urban Boquist <urban%boquist.net@localhost>]

28 jun 2009 kl. 15.39 skrev Jean-Yves Migeon:

> Does it happen only during domU start, or also during normal  
> operation, like when DHCP requests new leases?

All the domU:s are netbooting currently - so DHCP is only at boot
time. But I'll try to set up a new one and check that more carefully.

My feeling is that it might happen now and then also during
normal operation (I get NFS server not responding messages) but
the situation gets much worse when a new domU is started.

Also, during the time a new domU is created communication with
the other domU:s seems to be affected also. They "freeze" for say
half a minute. It's almost like the entire bridge
interface "stops" for a while.

    -- Urban

> Urban Boquist wrote:
> > some other people have reported UDP packet loss between domU and  
> dom0
> > (in bridge mode) but I understood that has mostly been under high
> > traffic load? I seem to get loss also with no load at all.
> >
> > Every time I start a domU I see lost DHCP replies and lots of NFS
> > retransmits. This is for a domU with root on NFS but I get the DHCP
> > problems also for a domU on local disk. At the same time the other
> > running domU:s seem to "freeze". After the domU is started it uses  
> NFS
> > over TCP and that seems to work better.
> >
> > Below are packet captures during boot, up to the NFS mount root
> > call. The DHCP offers come back from the DHCP server on physical wm0
> > but the first 7 never reaches the domU XVIF interface. Netstat shows
> > no packet loss.
> >
> > This is on a 8GB Quad core Xeon system - with zero CPU load in dom0
> > and a couple of other domUs. Week old -current amd64 dom0.
> >
> > I tried increasing the UDP send/receive buffers in dom0 but it  
> made no
> > difference.
> >
> > Any ideas?
>
> Does it happen only during domU start, or also during normal  
> operation, like when DHCP requests new leases?
>
> --
> Jean-Yves Migeon
> jeanyves.migeon%free.fr@localhost