netdev - Re: [v3 RFC PATCH 0/4] Implement multiqueue virtio-net

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Message-ID: <OFC29C4491.59069AD1-ON652577CA.00170F0D-652577CA.001C76C8@in.ibm.com>
Date:	Thu, 28 Oct 2010 10:44:14 +0530
From:	Krishna Kumar2 <krkumar2@...ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	anthony@...emonkey.ws, arnd@...db.de, avi@...hat.com,
	davem@...emloft.net, eric.dumazet@...il.com, kvm@...r.kernel.org,
	netdev@...r.kernel.org, rusty@...tcorp.com.au
Subject: Re: [v3 RFC PATCH 0/4] Implement multiqueue virtio-net

"Michael S. Tsirkin" <mst@...hat.com> wrote on 10/26/2010 04:39:13 PM:

(merging two posts into one)

> I think we discussed the need for external to guest testing
> over 10G. For large messages we should not see any change
> but you should be able to get better numbers for small messages
> assuming a MQ NIC card.

For external host, there is a contention among different
queues (vhosts) when packets are processed in tun/bridge,
unless I implement MQ TX for macvtap (tun/bridge?).  So
my testing shows a small improvement (1 to 1.5% average)
in BW and a rise in SD (between 10-15%).  For remote host,
I think tun/macvtap needs MQ TX support?

> > > > Results for UDP BW tests (unidirectional, sum across
> > > > 3 iterations, each iteration of 45 seconds, default
> > > > netperf, vhosts bound to cpus 0-3; no other tuning):
> > >
> > > Is binding vhost threads to CPUs really required?
> > > What happens if we let the scheduler do its job?
> >
> > Nothing drastic, I remember BW% and SD% both improved a
> > bit as a result of binding.
>
> If there's a significant improvement this would mean that
> we need to rethink the vhost-net interaction with the scheduler.

I will get a test run with and without binding and post the
results later today.

Thanks,

- KK

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