On Nov 3, 2009, at 8:38 AM, hank peng wrote:
2009/11/3 Micha Nelissen <mi...@neli.hopto.org>:
hank peng wrote:
I remember normal memory copy can also be done (chosen by user) by
DMA
engine on IOP80331(Intel embedded cpu, xscale arch), so why ppc
platform didn't make use of DMA doing memory copy, I think it can
increase performance, please correct me if I am wrong!
AFAIK the DMA engine has only an asynchronous mode (not very smart
IMHO).
This means you always have the overhead of context switch +
interrupt +
context switch, so the transfer has to be quite large for this to
pay off.
but if the amount of data I want to copy is big enough? can we benefit
from using DMA in such case?
Correct, we just don't make normal memcpy do this. There isn't
anything stopping specific call from using the async DMA API to get
memcpy behavior.
- k
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