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From "Michael Yates" <>
Subject RE: Memory leak- yeah I know
Date Thu, 15 Jan 2004 00:43:22 GMT
I spent some time a while back trying to get some reproducibility into
memory use in Tomcat (4.1.24)
I found that even sitting idle tomcats memory use would increase.

Here is my original mail to the tomcat-dev mailing list
 <<4.1.24 secure connector throws a LOT of garbage>> 

After I did some more investigations and figured out a fix the following bug
was raised

To reduce the amount of garbage thrown by tomcat I would recommend two
things, doing these might help you track down other memory issues.

1 - Use -Xmx<someValue>m -Xms<someValue>m.
The above sizes the heap to whatever value you put in there (note the value
is megabytes). I found (at least on the Solaris JVM) that sizing the heap
and making the min and max heap sizes the same not only sped up start up but
also made the garbage collector behave much better.

2- Set the serverSoTimeout value to 0 in the connector configuration in your
server configuration file. This will prevent the sever socket timing out.
Which DOES throw garbage, and if it is a secure connector you are using it
throws SO much garbage that the garbage collector can not keep up too well.

Using just number tip 1 above (as the fix to the bug above wasn't in Tomcat
4.1.x before we needed to go into production. We managed to run at something
like 100 TPS for 48 hours with no falling over and no net increase in memory

If you need any more information on the above let me know.

Michael Yates
Software Engineer, Location Center
Nortel Networks Wollongong, Australia.

-----Original Message-----
From: Filip Hanik [ <> ] 
Sent: Thursday, 15 January 2004 11:09 AM
To: Tomcat Developers List
Subject: RE: Memory leak- yeah I know

Remy, absolutely no intentions of being sarcastic :), if there isn't a leak,
that is great, if there is, will fix it.

I'm trying to figure it out, I didn't ask anyone else to spend time on it,
or even read my email. but if anyone is doing work on this lets work on it

just got jprobe up and running, once I have ran a few tests, I will
experiment with the garbage collection, the memory is slowly growing, its
been running for an hour.


-----Original Message-----
From: Remy Maucherat [ <> ]
Sent: Wednesday, January 14, 2004 3:08 PM
To: Tomcat Developers List
Subject: Re: Memory leak- yeah I know

Filip Hanik wrote:

> Ok, I know that these emails are usually dismissed with the words: 
> "Gets us some proof from a profiler", and I will...gimme some time, in 
> the meanwhile, if anyone else wants to play with it.
> well the story is that during heavy load tests of the session
replication my
> system my VMs always run out of memory.
> What am I doing different than others, well, during my load tests I am 
> not using keep alive connections to achieve true round robin. I'm
doing this by
> setting method.setHttp11(false) in the Http client.
> Running the test (attached, instructions below) I am hitting 
> http://localhost:8080/index.jsp <http://localhost:8080/index.jsp>  (home
page) and watching the
memory grow and
> grow and grow.
> I am using a profiler and having somewhat of a hard time reading
the output.
> I am gonna download a trial of jprobe, see how that works out for 
> me... I will be back with results from that.
> in the meantime, for those who want to see their memory grow here are 
> the instructions
> My env:
> Machine: PIII 1.6Ghz, 512MB Ram
> OS: Redhat 8
> VM: Sun JDK 1.4.2_02 (build 1.4.2_02-b03)
> Instructions:
> download the attached client.jar
> execute:
> java -cp testclient.jar;commons-httpclient.jar;commons-logging.jar
> org.apache.catalina.cluster.test.client.MemTestClient http 
> :// 100 100000 1000 false (exchange ; for 
> : on
> unix)
> Watching the memory grow using Top, although it shouldn't increase at 
> all.

There's ab for that kind of stuff, you know ... No need to waste your time
writing some new stuff. Your tone is a bit sarcastic, I think. I'm eagerly
awaiting your "proofs" ;-)


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