what are 'missing' pages?

[Steve Wampler]

I'm having trouble understanding the world.  Could some kind soul
provide some directions?

The world:
	uVAX-III with 16MB main memory and two 20MB swap partitions
	(not on the internal DEC disks but on two SCSI drives).
	Ultrix 2.2 OS.

We've had trouble lately with malloc()'s failing do to
'lack of core' or 'lack of swap space', even though we
are not approaching the total 56 MB above.  It looks
as though (I'm not sure because I don't really know how
to check) this happens when the total virtual memory
of running processes exceeds the amount of physical
memory (16MB).

Is this 'expected' behavior?  We're talking BIG malloc's
by the way - typically 1 to 3 MB.

Here's the output of 'pstat -s'

	11661k used (1357k text), 8781k free, 3240k wasted, 40781k missing
	avail: 13*512k 2*256k 3*128k 7*64k 10*32k 12*16k 269*1k

Now, can someone explain What This All Means?  In particular, since
there is ~40MB 'missing' and since this roughly matches our total
swap space, it makes me think that there *is* no swap space.  In
fact, 'vmstat -S' shows:

 procs     memory                       page      disk  faults          cpu
 r b w   avm  fre  si so  pi  po  fr  de  sr r0 r1 r2 r3  in  sy  cs us sy id
 2 0 0  3257 6833   0  0   0   0   0   0   0  1  0  2  0  71 156  56 12 14 74

See, no swap in's or out.
Here are the (current) sums of the SZ and RSS fields from 'ps -aux'

	   SZ     RSS
	14602	 4792

if that means anything.  Note that the number of resident pages is
quit a bit smaller than physical memory.  (The above total includes
the pages held by page daemon, if that means anything.)

Anyway, if someone can guide me in the true path to enlightenment, I'd
be effusively thankful.
-- 
	Steve Wampler
	{....!arizona!naucse!sbw}
	{sbw at naucse.cse.nau.edu}