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Home » Eclipse Projects » Memory Analyzer » Heapdump is too small
Heapdump is too small [message #652338] Thu, 03 February 2011 15:51 Go to next message
Frank  is currently offline Frank Friend
Messages: 2
Registered: February 2011
Junior Member
I am running an Active MQ server. 512MB is allocated to the app and the log says that the heap is 466MB. The monitoring tool (Panorama) confirms this. The monitoring tool also says the app is slowly leaking memory (over weeks) and now only reclaims 20% of the heap after a GC.

We did a heapdump and used MAT to analyze it. The heapdump file is only 92MB and MAT says the heap is 72MB. We see no leak.

Where are all the other hundreds of heap MBs going?
Re: Heapdump is too small [message #652579 is a reply to message #652338] Fri, 04 February 2011 15:35 Go to previous message
Krum Tsvetkov is currently offline Krum TsvetkovFriend
Messages: 163
Registered: July 2009
Senior Member
One possibility is that the GC which usually happens before the heap dump is triggered cleand up the memory.

Other posibility is that MAT decided a lot of objects are garbage, but as you say that the file is 92mb I would rather asume this is not the case.

Not sure that this will help me give you a better answer, but at least to get a better picture - what is the VM you are using (Sun / IBM). In which format is the dump (if this is an IBM VM) - a .phd file or a system dump?

Do you have some output from the VM about the GC activity, and about writing the heap dumps. Usually from sun VMs you'll see something like
Dumping heap to ...
Heap dump file created [<xxxxxx> bytes in <yyyyy> secs]

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