memory required to run webapp without outofmemory

[teoh <se...@yahoo.com>]

Free memory: 13.17 MB Total memory: 123.54 MB Max memory: 127.06 MB

is just by looking at tomcat manager, we can find out maximum memory
 required to run webapp without out of memory?

       
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RE: memory required to run webapp without outofmemory

["Caldarale, Charles R" <Ch...@unisys.com>]

> From: mgainty@hotmail.com [mailto:mgainty@hotmail.com] 
> Subject: Re: memory required to run webapp without outofmemory
> 
> first I would enable your PermGen memory collector
> http://my.opera.com/karmazilla/blog/2007/03/13/good-riddance-p
> ermgen-outofmemoryerror

Unfortunately, the entire premise of that blog is flawed.  The
statement:

"Objects in the permanent generation are never garbage collected; that
is, under normal circumstances when the jvm is started with normal
command line parameters."

is just blatantly false.  Why the author believes so is never made
clear, but it is clear from his later blog that his supposed "solution"
has nothing to do with his problem.

If you want evidence that the PermGen actually is collected, start
Tomcat with a large heap and JMX enabled, run some requests through a
reasonably complex app such as Lambda Probe, and look at the PermGen
with JConsole.  Undeploy the add and force some GCs - more than one may
be necessary - and the PermGen size will decrease (but probably not by
much).

 - Chuck


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Re: memory required to run webapp without outofmemory

[mg...@hotmail.com]

first I would enable your PermGen memory collector
http://my.opera.com/karmazilla/blog/2007/03/13/good-riddance-permgen-outofme
moryerror

M--
----- Original Message -----
Wrom: BARHDMNNSKVFVWRKJVZCMHVIBGDADRZ
To: <us...@tomcat.apache.org>
Sent: Sunday, December 02, 2007 7:51 PM
Subject: memory required to run webapp without outofmemory


>
> Free memory: 13.17 MB Total memory: 123.54 MB Max memory: 127.06 MB
>
> is just by looking at tomcat manager, we can find out maximum memory
>  required to run webapp without out of memory?
>
>
> ---------------------------------
> Be a better sports nut! Let your teams follow you with Yahoo Mobile. Try
it now.


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RE: memory required to run webapp without outofmemory

["Caldarale, Charles R" <Ch...@unisys.com>]

> From: teoh [mailto:second_comet@yahoo.com] 
> Subject: memory required to run webapp without outofmemory
> 
> is just by looking at tomcat manager, we can find out maximum memory
>  required to run webapp without out of memory?

Not really - it's much more complicated.  The JVM heap holds objects of
all types, including those from each webapp, ones used by Tomcat, ones
used by the JVM internally, etc.  The heap itself is partitioned into
various areas used for objects of different lifetimes, and garbage
collections occur when an area fills.  Looking at total heap usage at
any given instant of time won't really tell you what portion of the
usage depends on the number of requests that are being processed at that
instant.  Also, there's no guarantee that all requests will consume the
same amount of heap resources.

You generally want to configure the heap as large as you can without
provoking page swapping.  That will likely take some experimentation as
well monitoring.  JConsole provides a decent look at heap usage over
time, but you'll really nead a profiler if you want detailed information
about what your webapps are doing.

A link you may find interesting:
http://java.sun.com/javase/technologies/hotspot/gc/index.jsp

 - Chuck


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