On Thu, Oct 26, 2006 at 11:12:15PM +0900, Izumi Tsutsui wrote:
> > > - There are quite few packets which require padding.
> > 
> > It depends on the workload I guess.
> 
> Could you take any statistics on real machiens?
> I wonder what type of application will require such packets
> since on my macppc (mostly client) there are only less than
> 0.01% short packets on TX.

Lots of TCP ACK for example. 

> 
> > > - Such zeroed memory for padding has to be allocated by
> > >   bus_dmamem_alloc(9) and it wastes resouces only for rare packets.
> > >   (though most drivers have some room for padding in thier DMA descriptor
> > >    structures)
> > 
> > It's only 64 bytes, and only one time (you don't need one per interface)
> 
> But it also requires bus_dmamap_create() and bus_dmamap_load() calls
> which may consume some more resources and they are never freed.

Yes, but only once for the life of the system.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--