SUMMARY: 220R 2.6 possible memory leak?

From: Stephen Ryan <>
Date: Wed Apr 03 2002 - 06:39:29 EST

I had some concerns about a possible memory leak on a 220R (see below) 
Many thanks for the reassuring responses I received, all of which
indicated that my machine was behaving in a normal fashion (for a pre
Solaris 8 box, that is). 

Pyers Simon quoted Cockroft & Petit's "Sun Performance and Tuning": -
"When you look at vmstat, please don't waste time worrying where all the
RAM has gone. After a while the free list will stabilise at around 3%
(three) [which in your case is around 60MB] of the total memory 
configured. The system stops bothering to reclaim memory above this
level, even when you aren't recovering anything"

The buffer cache will consume free memory (largely for file data
caching) and applications requiring memory will reclaim it as required.

The main indicators of truly strained memory resources are excessive
page scanning/swapping rates. 

Kevin Buterbaugh indicated that so long as the scan rate didn't exceed
273 pages per second for extended periods then the system was healthy.
Michael Hocke suggested running Virtual Adrian or vmstat over time to
monitor these stats.
Darren Dunham suggested possibly turning on priority paging in the
Pyers Simon also sent me a copy of "The Solaris Memory System" by
Richard McDougall, which is currently being read ... : -
My thanks also to John Riddoch, Graham Rauxon and Peter Ondruska for
their speedy responses.


-=-=-=-=Original Question=-=-=-=-=-=-=-=

Hi all,

I have a 220R running 2.6 105181-28. It has 2gb of RAM. It is running as
our internal DNS master (BIND 8-22p5), NIS master and mail server. We
are running qmail 1.03 and UW imap 2001a.
The problem is that the physical RAM is constantly close to being maxed
out - it usually sits at about 32mb free. The biggest hog appears to be
imap (at present, 162 client sessions running, averaging about 5mb
usage), but even on slow days with far fewer imap clients the free RAM
count is still down around 32mb. I've seen references to file system
being a possible cause of this, but the implication is that this usually
happens over time - this machine maxes out within about 20 minutes of a
reboot. The automounter is mounting all the imap users' home
directories, so I'm wondering if it's an issue with nfs file caching.
I've run SymbEL zoom on the box and it doesn't squawk about the ram
consumption. vmstat over time reports healthy scan rates.
I suppose my question is: - Is this normal behaviour or am I looking at
a memory leak? If so, what are the optimal tools to detect the cause?
I've done some analysis using kmastat/crash, but nothing is leaping out
at me - I've been running comparisons with other, healthy boxes and the
bucket usage patterns appear consistent. As this is a production
machine, my actions in trying to isolate the fault have been restricted 
- should I be
thinking of an out of hours reboot and then bringing up the services
incrementally while monitoring the mem stats?
TIA for any help/info.

Stephen Ryan 
IT Group
Parthus Technologies plc
ph: +353-1-402 2579
fax: +353-1-402 5711
sunmanagers mailing list
Received on Wed Apr 3 05:42:20 2002

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