On Tue, Sep 14, 2010 at 11:21:15PM -0700, Shirley Ma wrote:

On Wed, 2010-09-15 at 07:12 +0200, Michael S. Tsirkin wrote:

quoted

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

Any other issue you can see in this patch beside vhost descriptors
update?

Another issue is that macvtap can be bound to almost
anything, including e.g. a tap device or a bridge,
which might hang on to skb fragments for unlimited time.
Zero copy TX won't easily work there.
I can imagine either somehow triggering a data copy after the
fact (hard), or detecting such devices and avoiding
zero copy (unfortunate for guest to guest, and drivers
will need tuning).

 Don't you think once I address vhost_add_used_and_signal update
issue, it is a simple and complete patch for macvtap TX zero copy?

Thanks
Shirley

I like the fact that the patch is simple. Unfortunately
I suspect it'll stop being simple by the time it's complete :)

-- 
MST