How to alert for heap fragmentation

[roz dev]

Hi All

I am using Java 6u23, with CMS GC. I see that sometime Application gets
paused for longer time because of excessive heap fragmentation.

I have enabled PrintFLSStatistics flag and following is the log


2012-10-09T15:38:44.724-0400: 52404.306: [GC Before GC:
Statistics for BinaryTreeDictionary:
------------------------------------
Total Free Space: -668151027
Max   Chunk Size: 1976112973
Number of Blocks: 175445
Av.  Block  Size: 20672
Tree      Height: 78
Before GC:
Statistics for BinaryTreeDictionary:
------------------------------------
Total Free Space: 10926
Max   Chunk Size: 1660
Number of Blocks: 22
Av.  Block  Size: 496
Tree      Height: 7


I would like to know from people about the way they track Heap
Fragmentation and how do we alert for this situation?

We use Nagios and I am wondering if there is a way to parse these logs and
know the max chunk size so that we can alert for it.

Any inputs are welcome.

-Saroj
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