Sticky Programs. /tmp in memory

[utzoo!decvax!ucbvax!hpvax!sri-unix!mike at BRL]

Mike -
	Our system has lots of stuff sticky, and it DOES make a big
difference.  Especially because swapping is on a separate controller
from the D-space fetch.  Being sticky saves CPU time (1 DMA -vs- many,
no block copying) and I/O time (1 continuous operation -vs- many).
They payoffs are less substantial, but still noticable, if you swap
on the same controller as /usr is on.

	Putting /tmp out in memory is a win, but putting it out on
the UNIBUS as a real controller has certain advantages.  Most importantly,
the xfer from the /tmp memory to the buffer cache is DMA for a real
controller, but it is a software copy the other way.  Of course, there
is the interupt overhead to pay when emulating a real disk.  Either
way is a big win over doing nothing.
						Cheers,
						 -Mike