SUMMARY: memory allocation

From: Tony Warner <Tony.Warner_at_gat.com>
Date: Wed, 12 May 1999 10:59:21 -0700

Thanks to the people who responded so quickly!

Basically, I was looking for a break down of real memory
usage.

Most people came back with using 'ps avx'.
this is nice since it sorts by physical memory use!
another good one was 'vmstat -P'.

This is just what I was looking for. Also, a couple of people
explained that the o/s uses as much memory as is can for
the currently running processes. Therefore, "Free Memory" is
a somewhat misleading number. It will often be quite low even
when there is very little running on the machine. The o/s
allocates memory as it is requested by processes.

-- 
There were some hints for kernel tuning, as well...
------------
Tony,
 Take a look that the tuning and performance manual. There are
instructions there for looking at the kernel structures. You 
can also install Performance Manager (pmgr), top (freeware, see
the archives for locations), or vmubc from Compaq :
ftp://gatekeeper.dec.com/pub/Digital/vmubc.tar.Z
among other places.
The usual suspect is vm-ubcmaxpercent which is the kernel 
param that controls how much memory the vm system is allowed to
use for i/o buffers and such. The default value is 100%. This
memory won't be released until another process requires it.
Alan Davis
------------
and ...
------------
Odds are it's the filesystem cache, which be default is set to a max of
50% of physical memory.  There's a parameter in sysconfigtab to change
it,
in the vm subsystem, of course.  I'm not sure what it is offhand, but it
is in the system tuning and configuration manual.  Technically, this
memory *should* be reclaimed by the system as it is needed, but of
course,
it does take some time to flush the cache, so performance is degraded.
Changing to 20 percent should solve your problem, and still leave a
reasonable sized cache.
Andrew
+-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-+
| Andrew Busch                      | email :    a.busch_at_qut.edu.au    
|
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Tony Warner						Tony.Warner_at_gat.com
General Atomics					(619) 455-4285
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Received on Wed May 12 1999 - 18:02:32 NZST