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List:       linux1394-devel
Subject:    Re: Large packet iso xmit trouble
From:       Stefan Richter <stefanr () s5r6 ! in-berlin ! de>
Date:       2009-12-25 18:23:30
Message-ID: tkrat.7bfec67ee7b38d45 () s5r6 ! in-berlin ! de
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Stefan Richter wrote:
> But another thing that should be tried is to interleave DMA descriptors
> and packet payloads into the same (series of) pages.  Then, the FireWire
> controller's DMA unit has to jump around less between different memory
> locations (read descriptor, read packet, write descriptor's status).

PS: Of course, controllers may prefetch descriptors, then at least the
'read descriptor' part is out of order WRT the other two parts.  Less
likely, but perhaps not entirely impossibly, the latter to parts could
also be executed out of order if not every packet is an interrupt
packet.
-- 
Stefan Richter
-=====-==--= ==-- ==--=
http://arcgraph.de/sr/


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