🚀 go-pugleaf

>UUCP:   seismo!umcp-cs!chris
>This analogy is flawed.  This would be true if one other thing were
>also true.  The delay produced by paging has to be noticeable when
>compared to other delays in the system.  The primary delay in the
>system is likely to be the user, and his delay is likely to be on
>the order of seconds, not milliseconds: thus the paging is lost in
>the noise.

	While your point has some validity it doesn't seem to invalidate
	my analogy. It still takes longer to get to point A from point
	B, you just mean that the guy rather get started quicker and hit
	some lights on the way, than wait to get on the on-ramp to the
	freeway.

	In this particular case you say that a user rather have a lot
	of fractional second delays while he is running his program,
	rather than say, an additional one second delay at start up
	time. This may be true, although the human factors stuff I've
	read doesn't support it. Just because the user takes several
	seconds to enter something, doesn't mean he allows the computer
	the same leeway. A lot of people, especially those weaned on
	microcomputers, are of the school that any response time that is
	long enough to be perceived is too long. Also consider what
	percentage of the time between when you ask to run, say an
	editor, and the actual prompt was actually spent loading the
	task into memory, and what was spent finding the shell script
	and running it and finding all the necessary files and assigning
	them etc. I suspect that on most non-trivial tasks these factors
	outweigh the actual task loading time. But, in any case, this
	is outside the the scope of this discussion, or even this
	newsgroup.

	One statement that is puzzling me that several people have made
	in this discussion is that you can run a program with 90%
	percent of its performance with 10% of the memory. When I
	worked as a system programmer on MVS systems the rule of
	thumb we used was that if a programs virtual memory was
	twice the real memory allocated to it, you were going to
	have page thrashing problems. Can someone provide further
	information on the 90/10 rule being quoted. What system and
	class of programs is this rule is applicable to. It seems to
	me that this could color peoples perception of the problem.
	After all there is a big difference in cost between doubling
	the real memory on a machine and adding ten times as much
	memory. Shucks what you save in paging devices could pay
	for doubling the memory. Disks fast enough to make good
	paging devices tend to be expensive.
-- 
     Joel Upchurch @ CONCURRENT Computer Corporation (A Perkin-Elmer Company)
     Southern Development Center
     2486 Sand Lake Road/ Orlando, Florida 32809/ (305)850-1031
     {decvax!ucf-cs, ihnp4!pesnta, vax135!petsd, akgua!codas}!peora!joel