🚀 go-pugleaf

> If big main memory gets REALLY cheap, maybe we won't need virtual memory any 
> more...

The odds are that the demand for address space will continue to grow faster
than the memory sizes.  In any case, people who argue on this basis miss an
important point:  virtual memory is not a substitute for real memory.  To
quote one of my friends over at HCR:  "real memory for real performance".
The point of virtual memory is not that it's as useful as real memory -- it
is useful in direct proportion to the extent to which it is backed by real
memory -- but that it turns a hard limit into a soft limit.  If you do not
have virtual memory, then a job which doesn't quite fit is unrunnable.  If
you do not have virtual memory, and your main memory is slightly over-
committed, then much more drastic measures like swapping will have to be
used, with much more serious impact on performance.  Virtual memory does
increase the effective size of memory for many applications (big number-
crunching things are often an exception, which is why virtual memory is
not popular in that community; it doesn't do them much good), but it also
makes performance degrade gradually, instead of sharply and disastrously,
when memory is slightly short.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,decvax,pyramid}!utzoo!henry