🚀 go-pugleaf

In article <1992Apr14.120306.2121@cubetech.com> andrew@cubetech.com  
(Andrew Loewenstern) writes:
 
[ ... Me writing about how simple it would be to repair the VM-swapfile
      problems and offering help to NeXT to solve it ... ]

> Maybe you should just break down and spend $300 on a dedicated 
> swap-disk.  You would be able to fix your problem much faster than 
> waiting around for NeXT.

Andrew, the whole point I was trying to make is that I don't have to wait  
for NeXT to fix it, because I measure my swap space in advance (I've been  
using my NeXT 12 Mb Color Station + Mathematica now for 6 months without  
crashing it for lack of swap space). What I wanted to express is that I  
want to help NeXT to overcome these problems, BECAUSE I THINK THEY'RE  
QUITE EASILY FIXED. Don't be fooled by the Organization: line of this  
post; before this life, I was a systems programmer at the largest academic  
computer centre in the Netherlands - I've seen (and corrected - or worked  
around) a lot of OS bugs.

Now the one of the ever increasing swap file is really easy, although the  
details depend on the actual implementation of page-in, page-out and  
page-not-resident-fault routines. The prime observation to make, is that  
the problem is: having a lot of 'actually' free pages in a swapfile bound  
at its highest 'page offset' by a non-free page. This page is used by a  
currently active application, so we have a valid vm-map for it. Now the  
point is that the OS should recognize that a lot of free disk space is  
'helt hostage' by the relatively few pages dedicated to this one process  
that doesn't go away, taking up the high-numbered pages in the swapfile.
This could be implemented by a simple heuristic. The action to take is:  
make the few pages 'at the top of the swapfile' resident (either by  
swapping them in, or by denoting them 'swapped in' because they weren't  
changed), mark them as 'not swapped out' and truncate the swapfile.

'Look ma, no hands'

--
Toon Moene (toon@moene.uucp)
Kantershof 269, 1104 GN  Amsterdam, The Netherlands
Tel.: + 31 20 6982029; Fax: + 31 20 6003411
No Disclaimers; a NeXT at home protects against this occupational hazard.