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From "Tlholoe, Peter" <>
Subject ActiveMQ heap size vs Commited Memory
Date Fri, 07 Sep 2012 08:48:05 GMT
We have increased the Java Heap Size in the wrapper.conf to 2048, and the systemUsage memoryLimit
to 1280 MB (estimating +-70% of the total heap size). When monitoring the message broker using
JMX console I see something interesting.

First our garbage collection takes 1 minute, sometimes 3 minutes. Sounds like we have major
problems here, a gc that takes such a long time is worrying

*         Garbage collector:

Name = 'PS MarkSweep', Collections = 269, Total time spent = 1 minute

*         Garbage collector:

Name = 'PS Scavenge', Collections = 73,136, Total time spent = 3 minutes

Even though we set the Heap size to 2048,  we also see the following

*         Current heap size:

  155,121 kbytes

*         Maximum heap size:

1,864,192 kbytes

*         Committed memory:

350,720 kbytes

My understanding of the Committed memory is the amount of memory guaranteed to available for
use by the concerned JVM. Isn't this supposed to reflected the 2048 that we have allocated
to the VM.

Machine stats
Operating System:

Linux 2.6.18-274.17.1.el5



Number of processors:


Committed virtual memory:

2,792,076 kbytes

Total physical memory:

32,962,524 kbytes

Free physical memory:

   413,200 kbytes

Total swap space:

 2,097,144 kbytes

Free swap space:

 2,097,008 kbyte

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