Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!samsung!uunet!zephyr.ens.tek.com!tekadg!tonyr
From: tonyr@tekadg.ADG.TEK.COM (Tony Rick)
Newsgroups: comp.sys.mips
Subject: Where does the memory go - I forget ...
Keywords: memory, virtual
Message-ID: <871@tekadg.ADG.TEK.COM>
Date: 2 Aug 90 19:27:05 GMT
Distribution: usa
Organization: Tektronix Inc., Beaverton, Or.
Lines: 49


Fellow MIPSians,

     My question is: Where does the memory go?

     The reason I ask this is that we run some large processes, 
whose sizes are reported by ps to be >5000 pages.  When one of these 
runs, uncontested, the system response goes way down, vsar show much 
swapping and paging, and very few freemem pages available, <250.  

     I have an m120-5 with 32Mbyte memory.  At boot time the console
eventually says "Available memory = 30367744" which I take to mean
a byte count of memory left after the OS has claimed it share.  I also
think 32Mbyte means 1024*1024*32=33554432 bytes.  So my simple
arithmetic skills tell me that the OS has 3186688 bytes(778 pages).  
A 'ps -el' snapshot shows 27 processes with a total of 909 pages or clicks 
(what is a 'click'?).  Now some of these processes report less than 25 (pages 
or clicks), and there is a tuneable kernel parameter MINARMEM, default
value 25, that specifies a minimum number of text and data pages
reserved for a user process.  Taking that into account, as a worst case
estimate in my search for memory, I can say that the total number of
pages accounted for by that 'ps -el' snapshot is 1053.  Now a 'vsar -r'
snapshot says that there are 4508 pages (freemem) available for user processes.
All of this information gathering happenned right after boot before any
major accumulation of operating history, well, not more than about 5
minutes.

Hmm...

That's        8192 pages total in the system, (pagesize = 4096),
	778        pages occupied by OS
       1053        pages occupied by user processes
       4508        pages of freemem
       -------------
       6369        pages in use accounted for
	      1823 pages unacccounted for (7467008 bytes)

That is a considerable amount of the memory.

When we first got the machine, it had 24Mbyte (3 memory boards).  I
added one more later ( we had the 'self service' type of support then ).
Did I miss something when I put the new board in?  Did I miss something
in searching for memory?  What's happenning?  Where does the memory go?
Help, Mister Wizard!

tony rick
Tektronix, Inc.  Beaverton, OR
email:tonyr@tekadg.adg.tek.com
voice:503-627-2942