SysIII swapping strangeness

[John Kullmann]

The stock swap algorithm will swap out a process which
has been in memory for 2 seconds (regardless of whether it
got *any* cpu time or not since it was swapped in) and swap 
in a selected swapped out process that has been out for 
at least 2 seconds.

Consider a heavily memory (over)loaded system, sometimes
swapping continuously for 5-20 minutes at a time. Is it
possible that processes are being swapped in and back out 
many many times before they actually run? (some of these
processes are > 500Kb).

A few questions:
1) Is this 2 second business left over from the pdp11
	where the address spaces were smaller?  Should
	I/do people change this?
2) Shouldn't the swapper be changed to at least let the
	poor sucker get a few ticks before letting him
	go back out?
3) Do all un*x systems (before demand paging came around)
	slow way,way,way down when anything but trivial
	swapping is occurring?
4) Has anyone else researched this? If so, please save me
	some time and respond...

John Kullmann
...decvax!sun!plx!jk