RE: Calculating Physical memory for Oracle Sessions
- From: "Jesse, Rich" <Rich.Jesse@xxxxxx>
- To: <jkstill@xxxxxxxxx>
- Date: Thu, 30 Nov 2006 13:13:18 -0600
Jared, wouldn't your formula multiply shared memory (e.g. Oracle SGA
size as reported by "ipcs -ma") by the number of Oracle processes
(except for procs that don't connect to the instance, like the
listener)? I think using ps output that way would be like saying that
adding 25% of "X" and 25% of "Y" must equal 50% of "X+Y".
While I've never taken the time (had the time?) to dealve into it, I
think that pmap is accurate iff shared memory is accounted for. The
trick is to determine if any other process is accessing that shared
memory. My knee jerk is that this could be accomplished by making a
"master" list of shared memory (possibly using pmap outputs) to evaluate
against whatever subset of processes you would want to see.
This blog item mentions this problem, but doesn't really offer a
solution:
http://virtualthreads.blogspot.com/2006/02/understanding-memory-usage-on
-linux.html
Kinda wierd that no one's thought of a solution (even if it's only a 99%
one) to this, ain't it?
My $.02,
Rich
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Jared Still
Sent: Thursday, November 30, 2006 11:18 AM
To: panandrao@xxxxxxxxx
Cc: tim@xxxxxxxxx; ORACLE-L
Subject: Re: Calculating Physical memory for Oracle Sessions
On 11/29/06, Anand Rao <panandrao@xxxxxxxxx> wrote:
Tim,
There are lots of good AIX goodies for processes :)
From AIX 5.3, procmon is a great to use that gives you a more
detailed and elaborate "pmap" like service.
procmon is a GUI tool (but surprising useful unlike many
others).
Are they accurate?
It has the following options to perform detailed process
analysis,
procfiles
..
Of course, pmap is much easier to use as it is a single
command-line tool.
Here's why I asked about the AIX memory tools.
pmap is notoriously inaccurate. Memory accounting tools in Linux don't
work too well. Try adding up all the memory reported by
ps -fywluoracle | awk '{ mem=mem+$8 } END{ mem=mem*1024; print "bytes:
", mem}'
on a linux box, and it will be quite a bit more than actual do to double
or triple counting of memory against RSS.
The same situation may exist on AIX, as it is my understanding that many
unix's suffer from this malady.
--
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist
Other related posts:
