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

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Date:	Tue, 26 Oct 2010 13:09:13 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Krishna Kumar2 <krkumar2@...ibm.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, netdev-owner@...r.kernel.org,
	rusty@...tcorp.com.au
Subject: Re: [v3 RFC PATCH 0/4] Implement multiqueue virtio-net

On Tue, Oct 26, 2010 at 03:31:39PM +0530, Krishna Kumar2 wrote:
> > "Michael S. Tsirkin" <mst@...hat.com>
> >
> > On Tue, Oct 26, 2010 at 02:38:53PM +0530, Krishna Kumar2 wrote:
> > > 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 started binding vhost thread
> after Avi suggested it in response to my v1 patch (he
> suggested some more that I haven't done), and have been
> doing only this tuning ever since. This is part of his
> mail for the tuning:
> 
> > 		 vhost:
> > 		 		 thread #0:  CPU0
> > 		 		 thread #1:  CPU1
> > 		 		 thread #2:  CPU2
> > 		 		 thread #3:  CPU3
> 
> I simply bound each thread to CPU0-3 instead.
> 
> Thanks,
> 
> - KK
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