🚀 go-pugleaf

Excerpts from netnews.comp.sys.next.misc: 10-Dec-92 Re: Swapfile
compression by Paul Lynch@seer.demon.co 
> It's not *extra* diskspace (if I read your intention correctly).   
> swapfile.front is just a view onto swapfile; the only file that occupies  
> real disk space is swapfile.

Correct.
  
> Apart from that, I'd would also like to know what good turning it on will  
> do.  I find it hard to be convinced that compressing (which takes time) a  
> swapfile (which MUST be fast) is a good idea.

The idea is that it's faster for the CPU to compress and then write out
a smaller amount of data than it it to simply write out uncompressed
data.  There's a tradeoff made between CPU usage and disk I/O.

NeXT has set up the defaults so that machines that will do a lot of
swapping (low memory machines), and thus be I/O bound, will use swapfile
compression to shift some of the burden over to the CPU.  Machines with
more memory will not swap as much, and are not as I/O bound, so turning
on the swapfile compression may not help as much, or may actually
decrease overall performance.

-Chuck

+------------------------------------------+ "Foosh.  Aaughh!!"
| Charles William Swiger -- CMU...crunch!  | "Foosh.  Aauuggghh!!"
| AMS & normal mail: cs4w+@andrew.cmu.edu  | "Cold spray deodorant...."
| NeXTmail: chuck@mon.slip.andrew.cmu.edu  |
+------------------------------------------+   -- Opus, Bloom County [RIP]