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From Torsten Mielke <tors...@fusesource.com>
Subject Re: ActiveMQ heap size vs Commited Memory
Date Mon, 10 Sep 2012 07:44:21 GMT
On the total time spent for the garbage collector, this is not the time spent when the garbage
collector was run the last time, its the total time spent on garbage collection since the
JVM has been started. 

Regards,

Torsten Mielke
torsten@fusesource.com
tmielke@blogspot.com


On Sep 7, 2012, at 10:48 AM, Tlholoe, Peter wrote:

> 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
> 
> Architecture:
> 
> amd64
> 
> Number of processors:
> 
> 8
> 
> 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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