RE: [Xen-devel] performance problems...

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

>  > I'm using xen-3.0-testing from a week or two ago, and am
> > finding that a recompile of xen-3.0-testing from hg now is
> > all but killing the performance in the other domains.
> >
> > I am running an almost default setup, I've just made some
> > small changes to bridging.
> >
> > Any suggestions as to where to start? Or is this a known and
> > solved problem in the latest -testing?
> 
> There have been no changes in 3.0-testing that are likely relevant. I
> don't think anyone else has reported this, so I'd look closely at your
> bridging changes. Also please report the test setup in more detail.
You
> haven't connected dom0 directly to the bridge rather than vif0.0 to
the
> bridge have you?

Hmmm... I'm not quite sure what you mean here... I always thought that
in dom0 you just connected eth0 (or whatever you might have renamed it
to) into the bridge. Is this not the case?

'brctl show' gives me:
br0             8000.00508bea6159       no              trunk
br1             8000.00508bea6159       no              br0.2
                                                        vif2.0

I have an Ethernet interface called 'trunk', which is bridged to br0.
br0 then has vlan's on it (the vlan's have to be on the bridge
interface, not on the Ethernet interface, or it doesn't work!), giving
br0.2, which is in turn bridged into br1. The affected DomU is using
br1. None of br0, br1, or trunk have an ip address on them in Dom0. I
have another Ethernet interface called 'lan', which is a gigabit
interface and give's dom0 its connection to the lan, including ATA over
Ethernet. Anything hanging off of 'trunk' is purely for the use of
domU's. Only Dom0 does AoE, All domU's get their disk access via block
devices (which are themselves AoE) exported from dom0.

The slowdown is very very obvious, running a 'make world' in dom0 brings
domU to an almost standstill. Ctrl-Z on the make in dom0 instantly
brings domU back to life. Even if I disable the Ethernet interface in
domU (ifdown eth0), it still runs really really slowly. The system load
goes up in domU too, if that means anything.

Thanks

James

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