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From "Allistair Crossley" <>
Subject RE: Strage Behaviour - Tomcat Memory Leak
Date Thu, 05 Aug 2004 17:36:31 GMT
	As Yoav points out, this is quite normal. I also run JProbe and if you just leave it alone,
very small memory usage is made and at regular intervals the GC will jump in, producing your
saw tooth (since the GC will only jump in when it really thinks the heap needs clearing out
is why it gets quite high).
	Also when you say the "heap is totally filled" I don;t think you mean that the total memory
available to Tomcat is filled, e.g 128-512MB or whatever. What you mean is that the heap used
is filled and I bet that heap size is actually only about 7Mb or so if as you claim it is
just a startup of Tomcat. Therefore it is quite possible that it looks alarming but it is
not really.
	Cheers, ADC. 
	-----Original Message----- 
	From: Peter Lin [] 
	Sent: Thu 05/08/2004 17:55 
	To: Tomcat Users List 
	Subject: Re: Strage Behaviour - Tomcat Memory Leak

	I've used JProfiler in the past and I found it somewhat unreliable,
	since it is pretty heavy weight. I should say it was based on a half
	dozen tests using JProfiler and not a scientific evaluation.
	it was the free eval version a couple years back. I find optimizeIt
	more reliable for me and a little less heavy weight. I've use
	OptimizeIt in the past and tomcat without any requests shows flat
	memory usage. in other words constant.
	On Thu, 5 Aug 2004 13:39:44 -0300, Roberto Rios
	<> wrote:
	> Hi,
	> I was doing an evaluation of JProfiler in order see the improvements did
	> since the last time I used it. I has a feature (like other profilers) that
	> shows the heap usage in real time.
	> As I always do, I have installed a new copy of tomcat, with NO changes. I
	> have just unziped it into a directory (by the way, I am using winXP,
	> J2SDK1.4.2_05, JProfiler 3.1 and tomcat 4.1.30/5.0.25).
	> So I started JProfiler, that automatically starts tomcat (I have tested it
	> against 4.1.30 and 5.0.25 - same behaviour), and I also started the heap
	> monitor (that JProfiler calls VM Telemetry).
	> What I saw, IMHO, is very strange: time to times (around every 30 minutes)
	> the heap is totally filled, and the garbage collector runs. So the graph
	> looks like a saw:
	>  /|  /|  /|  /
	> / | / | / | /
	> /  |/  |/  |/
	> What is strange, is that I does't touch tomcat. I just start it. Nothing is
	> running under it (except the default applications: manager, examples,
	> etc.... Anyway, I have cleaned the server.xml and webapps, removing the
	> manager, admin and examples app. Same bahaviour again).
	> IMHO, the heap usage should be a flat line if nothing is running under
	> tomcat. Something like (the initial increase is due to tomcat startup) this:
	>  /----------
	> /
	> /
	> My conclusion, is that OR tomcat has a huge memory leak, OR JProfiler isn't
	> reliable.
	> Does anyone has an explanation about this behaviour? Is it know? Maybe a
	> listener, logger, etc?
	> TIA,
	> Bob
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