Hi Mark,
as interesting as your point is, that's not something that
can be fixed within the scope of GNU Radio or even UHD...
Anyhow, I'm not really convinced that multiple DMA transfers are always
faster than copying data using memcpy - at least if those DMA transfers
copy only a few kilobytes, as is the case with packets from network devices.
The fact that packets are of limited size is not really a problem of
current computing architectures - it's a consequence of having packet
networks. Of course, it would be nice if your hardware would be able to
actually stream data into your userland, that somehow has the (zero
overhead) capability to tell the hardware to send the next sample - but
in reality, hardware-to-cpu-transfers usually happen en block, and that
is just fine for most applications, since there is little use of having
samples one after another; therefore, some buffering is always necessary
(and will always be).
For the sake of adaptivity, hardware supplied data most probably won't
be written to copy device data to multiple RAM addresses, since the data
from the device usually needs some processing (hence the driver).
So in effect, in most imaginable cases a device will do a single
DMA transfer to RAM.
Greetings,
Marcus
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