netdev - Re: [RFC PATCH 2/2] macvtap: TX zero copy between guest and host kernel

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Message-ID: <20100915051241.GA25340@redhat.com>
Date:	Wed, 15 Sep 2010 07:12:41 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Shirley Ma <mashirle@...ibm.com>
Cc:	Arnd Bergmann <arnd@...db.de>, Avi Kivity <avi@...hat.com>,
	"Xin, Xiaohui" <xiaohui.xin@...el.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] macvtap: TX zero copy between guest and host
 kernel

On Tue, Sep 14, 2010 at 12:36:23PM -0700, Shirley Ma wrote:
> On Tue, 2010-09-14 at 21:01 +0200, Michael S. Tsirkin wrote:
> > > > I think that you should be able to simply combine
> > > > the two drivers together, add an ioctl to
> > > > enable/disable zero copy mode of operation. 
> > > 
> > > That could work. But what's the purpose to have two drivers if one
> > > driver can handle it?
> > > 
> > > Thanks
> > > Shirley
> > 
> > This was just an idea: I thought it's a good way for people interested
> > in this zero copy thing to combine forces and avoid making
> > the same mistakes, but it's not a must of course. 
> 
> Ok, I will make a simple patch by reusing Xiaohui's some vhost code on
> handling vhost_add_used_and_signal() to see any performance changes.
> 
> The interesting thing here when I run 32 instances netperf/netserver I
> didn't see any issue w/i this patch.
> 
> Thanks
> Shirley

Yes, I agree this patch is useful for demo purposes:
simple, and shows what kind of performance gains
we can expect for TX.

-- 
MST
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