netdev - Re: [PATCH 2/2] vhost_net: a kernel-level virtio server

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Message-Id: <200908131658.06522.arnd@arndb.de>
Date:	Thu, 13 Aug 2009 16:58:06 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	virtualization@...ts.linux-foundation.org,
	"Ira W. Snyder" <iws@...o.caltech.edu>, netdev@...r.kernel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] vhost_net: a kernel-level virtio server

On Thursday 13 August 2009, Michael S. Tsirkin wrote:
> > Right now, the number of copy operations in your code is the same.
> > You are doing the copy a little bit later in skb_copy_datagram_iovec(),
> > which is indeed a very nice hack. Changing to a virtqueue based method
> > would imply that the host needs to add each skb_frag_t to its outbound
> > virtqueue, which then gets copied into the guests inbound virtqueue.
> 
> Which is a lot more code than just calling skb_copy_datagram_iovec.

Well, I don't see this part as much of a problem, because the code
already exists in virtio_net. If we really wanted to go down that road,
just using virtio_net would solve the problem of frame handling
entirely, but create new problems elsewhere, as we have mentioned.

	Arnd <><
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