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From: benseb@nic.cerf.net (Booker Bense)
Newsgroups: comp.sys.next,comp.arch
Subject: Re: Lost pages in swapfile ?
Keywords: NeXT, swapfile
Message-ID: <332@nic.cerf.net>
Date: 16 Apr 91 14:36:48 GMT
References: <1991Apr15.153504.39750@slate.mines.colorado.edu>
Followup-To: comp.sys.next
Organization: San Diego Supercomputer Center @ UCSD
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In article <1991Apr15.153504.39750@slate.mines.colorado.edu> mfriedel@slate.mines.colorado.edu (Friedel Michael) writes:
>After I boot my NeXTstation I typed vm_stat which is supposed to list
>the status of the virtual memory. Here is the result:
[ vm-stat stuff deleted ]
>
>My system is 12meg (of which 11 meg are available, 1meg is reserved
>by the system at boot time for buffers, so it tells me).
>The swapfile has a size of 20971520 bytes after the machine is done
>booting. Now no matter how I twist my math, I can't come up with 
>enough pages that justify a 20meg swapfile.
>So does anyone know to do the correct math, does vm_stat list incorrect
>statistics or does the system just forget about a few pages ?
>


-RTFM %-)! if you have it %-(! , the swap file has a low water mark
set in the file /etc/swaptab ( or something like that ). It's set so
the swapfile is never shrunk to less than 20 MB. The rule of thumb is
that the low water mark of the swap file should be twice the real
memory. You can think of this a ``reserved space'' on your disk, so
the system won't run out of swap space when it needs it.

 Now, for an 8 meg system 20 meg sounds a bit large. Since my 200 Meg
disk is rather cramped, I'd like to ask the NeXTperts, if you think
it'd be safe to set the low water mark lower ( like 16 meg ) . What
kind of bad things happen to the OS when it runs out of swap disk?

- Booker C. Bense                    
prefered: benseb@grumpy.sdsc.edu	"I think it's GOOD that everyone 
NeXT Mail: benseb@next.sdsc.edu 	   becomes food " - Hobbes