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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] Re: [PATCH 9/9] Introduce VLANClientState::cleanup()
Date: Wed, 29 Apr 2009 11:37:56 +0100
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To: qemu-devel@nongnu.org
Cc: Mark McLoughlin <markmc@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Marcelo Tosatti <mtosatti@redhat.com>, Markus Armbruster <armbru@redhat.com>

> > I'm still not understanding. Ethernet devices are fundamentally based
> > around a bus architecture. "flip the TX/RX queues" only makes sense if
> > you're talking about a point-point connection. For ethernet devices I see
> > no reason to distinguish between "host" devices (slirp, vde, tap) and
> > "guest" devices. They may be created for different reasons, but they're
> > all doing fundamentally the same thing.
>
> In the bus model, there's an implicit copy-to-the-wire operation that
> results in replication of the packet to everything else on the bus.
>  From a performance perspective, this is not at all ideal.

I'm not convinced by this argument. I don't see why a one-many api requires a 
copy.

Paul