That makes sense. Look at the I/O bandwidth of your CPU. To do the
copy_to/from_user it takes coping the data -in- to the CPU as well as
copying it back -out- of the CPU. This is time and bus bandwidth
consuming. Even if you have a recent system (P2 or P3 with 100Mhz bus,
possibly even a K6-2 or K6-3 with a 100Mhz bus) this takes a lot of the
bus bandwidth that would presumably be better off used for the
processing of the data rather than the simple copying of it. You can
only send or receive data at that rate for a short time before your low
on memory and need to do something with it...
Intel x86 CPUs still fall pretty far behind in the I/O bandwidth per
CPU category. This is where the newest Alpha's and other higher end
systems shine.
Greg
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