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From: dplatt@teknowledge-vaxc.ARPA (Dave Platt)
Newsgroups: comp.unix.wizards
Subject: BSD4.2 paging heuristics and vadvise(VA_ANOM)
Message-ID: <15056@teknowledge-vaxc.ARPA>
Date: Mon, 27-Jul-87 20:49:36 EDT
Article-I.D.: teknowle.15056
Posted: Mon Jul 27 20:49:36 1987
Date-Received: Sun, 2-Aug-87 22:06:36 EDT
Organization: Teknowledge, Inc., Palo Alto CA
Lines: 27

I'm running an application on a Sun 3/52 workstation that is pushing
the memory limits of the machine... it's a 2.8-meg LISP image on a
4-meg machine (i.e. 10 pounds of worms in a 5-pound can).  Needless to
say, the machine spends a lot of its time swapping pages (I think I
can smell the voice-coil in the 140-meg shoebox overheating ;-).

I tried hacking in a call to vadvise, to inform the kernel of the
potential "anomalous" memory behavior of the LISP image... and
performance got worse, rather than better.  I take this to mean that
in my particular case, the LISP image is accessing memory in a
sufficiently regular fashion that the standard "choose a page to write
or discard" heuristic is doing more good than not.

Three questions for the BSD gurus:

1) What is the normal heuristic used to choose a page to be swapped
   out to disk... least recently used?  Usage statistics?

2) What changes if I call vadvise(VA_ANOM)?

3) What's the best book available on the BSD kernel for someone
   interested in learning more about these arcane matters, assuming
   that I don't have a source license from Sun?

advTHANKSance for any information that you can provide.

		dave platt