Question about memory

Piercarlo Grandi pcg at aber-cs.UUCP
Thu Apr 12 08:27:48 AEST 1990

In article <1990Apr11.024731.11955 at nebulus.UUCP> root at nebulus.UUCP (Dennis S. Breckenridge) writes:
  In article <156 at cms2.UUCP> alan at cms2.UUCP (Alan McCain) writes:
  > memory in their system.  They said that when their system goes into swap it
  > never seems to come out of it completely, even when everyone logs off.  I
  > have the same situation.  Whey does this happen and can it be fixed?

  If memory is a problem BUY MORE memory! A rule of thumb for the 386
  machines running a UNIX (not Xenix) kernel is 4 megs for o/s and 1 meg for
  every Simultask user. If all of your apps are *nix, then take your best
  guess, you are safe with 1 meg per user. 

The problem is not memory, is the stupidty of the swapper (and who wrote it,
or failed to rewrite it). Look again at your figures: 1 MB per user is also
more or less what all vendors recommend.

Now ask yourself: how many user processes approach 1 MB in *size*? how many
user processes have a working set approaching 1 MB? How much memory should
be left unused to avoid the problems with the System V swapper

The answer to the latter question is ******80-90%******. If you configure
your system with less than 5-10 times the memory required


the System V swapper will make your life miserable.
Piercarlo "Peter" Grandi           | ARPA: at
Dept of CS, UCW Aberystwyth        | UUCP: ...!mcvax!ukc!aber-cs!pcg
Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg at

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