STREAMS overhead (was: SVR3.0 vs BSD4.3)

[Doug Gwyn]

In article <4441 at megaron.arizona.edu> lm at megaron.arizona.edu.UUCP (Larry McVoy) writes:
>(It should be obvious but I'll drive it home:  the streams code that I've
>seen copies the data out of the upper level buffer and then into the 
>lower level buffer [assuming "downward" movement].

The only data copy that should normally take place is between user-mode
data space and the nearest streams buffer, also between the farther
streams buffer and the net device.  Streams module-to-module data
transfer should occur by transferring packet pointers whenever possible.
(I haven't examined SVR3 code to see if this is how it typically does
things.)