netdev - Re: [RFC] kvm tools: Implement multiple VQ for virtio-net

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Date:	Sun, 13 Nov 2011 17:32:44 +0200
From:	Sasha Levin <levinsasha928@...il.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	penberg@...nel.org, kvm@...r.kernel.org, mingo@...e.hu,
	asias.hejun@...il.com, gorcunov@...il.com,
	Krishna Kumar <krkumar2@...ibm.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [RFC] kvm tools: Implement multiple VQ for virtio-net

On Sun, 2011-11-13 at 17:00 +0200, Sasha Levin wrote:
> On Sun, 2011-11-13 at 12:24 +0200, Michael S. Tsirkin wrote:
> > On Sat, Nov 12, 2011 at 12:12:01AM +0200, Sasha Levin wrote:
> > > This is a patch based on Krishna Kumar's patch series which implements
> > > multiple VQ support for virtio-net.
> > > 
> > > The patch was tested with ver3 of the patch.
> > > 
> > > Cc: Krishna Kumar <krkumar2@...ibm.com>
> > > Cc: Michael S. Tsirkin <mst@...hat.com>
> > > Cc: Rusty Russell <rusty@...tcorp.com.au>
> > > Cc: virtualization@...ts.linux-foundation.org
> > > Cc: netdev@...r.kernel.org
> > > Signed-off-by: Sasha Levin <levinsasha928@...il.com>
> > 
> > Any performance numbers?
> 
> I tried finding a box with more than two cores so I could test it on
> something like that as well.
> 
> From what I see this patch causes a performance regression on my 2 core
> box.
> 

[snip]

After discussing it with Michael, we found out that for a single TCP
flow the guest signals the same TX VQ, but the RX VQ keeps changing -
which means that theres missing host-guest synchronization of hash flow.

-- 

Sasha.

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