Summary for Protection in Cray

[Dik T. Winter]

In article <DREIER.91Jan13223533 at husc9.harvard.edu> dreier at husc9.harvard.edu (Roland Dreier) writes:
 > I guess one thing that should be noted about how Crays handle memory: under
 > Unicos, since it lacks virtual memory, whole jobs get swapped.  What this
 > means is that if I'm running two jobs on a 256 megaword machine and each of
 > them wants 129 megawords of memory, every time a job gets swapped out, I
 > have to do 129 megawords of IO, rather than just the small amount of overlap
 > that I "really" have to do; so clearly, even a slightly slower virtual memory
 > system would be at an advantage here.
 > 
But this is not a defect of the lack of VM; it is a defect of the OS.
If the OS wants to swap out the complete job it can do so, but it is
not necessary.
--
dik t. winter, cwi, amsterdam, nederland
dik at cwi.nl