netdev - Re: [PATCH] macvtap: Fix macvtap_get

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Message-ID: <20111127172333.GD31987@redhat.com>
Date:	Sun, 27 Nov 2011 19:23:34 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	David Miller <davem@...emloft.net>
Cc:	krkumar2@...ibm.com, jasowang@...hat.com, arnd@...db.de,
	levinsasha928@...il.com, netdev@...r.kernel.org,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] macvtap: Fix macvtap_get_queue to use rxhash first

On Fri, Nov 25, 2011 at 01:35:52AM -0500, David Miller wrote:
> From: Krishna Kumar2 <krkumar2@...ibm.com>
> Date: Fri, 25 Nov 2011 09:39:11 +0530
> 
> > Jason Wang <jasowang@...hat.com> wrote on 11/25/2011 08:51:57 AM:
> >>
> >> My description is not clear again :(
> >> I mean the same vhost thead:
> >>
> >> vhost thread #0 transmits packets of flow A on processor M
> >> ...
> >> vhost thread #0 move to another process N and start to transmit packets
> >> of flow A
> > 
> > Thanks for clarifying. Yes, binding vhosts to CPU's
> > makes the incoming packet go to the same vhost each
> > time. BTW, are you doing any binding and/or irqbalance
> > when you run your tests? I am not running either at
> > this time, but thought both might be useful.
> 
> So are we going with this patch or are we saying that vhost binding
> is a requirement?

I think it's a good idea to make sure we understand the problem
root cause well before applying the patch. We still
have a bit of time before 3.2. In particular, why does
the vhost thread bounce between CPUs so much?

Long term it seems the best way is to expose the preferred mapping
from the guest and forward it to the device.

-- 
MST
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