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From: gerrit@sequent.com
Newsgroups: comp.sys.next
Subject: Re: Lost pages in swapfile ?
Keywords: NeXT, swapfile
Message-ID: <1991Apr17.174031.28031@sequent.com>
Date: 17 Apr 91 17:40:31 GMT
References: <1991Apr15.153504.39750@slate.mines.colorado.edu> <332@nic.cerf.net> <1991Apr17.013649.532@arizona.edu>
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Several people ask why the swap file is larger than it seems to need to
be and if it can be smaller than it is.  First, it is statically allocated
to the size specified in /etc/swaptab at boot.  Sure, this number can be
smaller; I often set it to 16 Meg on some smaller machines.  If necessary
(and possible!) the OS will allow the file to grow if your applications
need more swap space.  However, by staking out a claim to 16 or 20 Meg from
the very beginning, you can lessen the chance that your application will
be killed due to lack of swap space when your disk fills up.

You could probably even make the size of the swap file as small as 12 meg
without noticing any real differences for a while (I haven't tried this one
though).  The catch is that if you do any "real" work on the machine (i.e.
using more than 4-5 NeXT Apps at a time), the swap file is quite likely to
grow back to what it used to be.

Something to try would be to set it to 8-10 Meg, run with your standard
environment for a while and see how large the file is.  Then you can
pre-allocate the space to match your needs, be they 6 Meg or 80 Meg.
Running out of swap space can cause all kinds of bad things to happen, so
it is better to run out of disk space with a comfortable size swap file
allocated.

gerrit