Thursday, October 2, 2014

Fun run of JClarity Censum - Garbage Collection analysis tool

I have downloaded the 14 days trial of JClarity Censum. It's EXTREMELY simple to use and gives you a quick feedback on your GC issues.

First, you HAVE to enable a few flags: -XX:+PrintTenuringDistribution and -XX:+PrintGCDetails (safe in PROD). Then you run your tests for some 24 hours and feed your GC log into Censum.

It gives you statistical info like:

Longest GC pause (I had 5 seconds, quite bad)

Percentage of time spent in GC pauses (mine is 9%, pretty bad, should be max 5%)

Average memory allocation rate (I had 90 MB / second, quite bad)

Max memory allocation rate (I had 900 MB / second, horrible)

Total Full GC pause time, and Total Pause time

Full GC to GC ratio (mine was 45%, pretty stiff)

Application throughput (percentage of time spent working, versus time spent in GC.... should be 95% or more)

The graphs are breathtaking...

All in all, they charge you a quite hefty (ANNUAL!) fee for this software... to perform analysis that doesn't seem all that complicated - I am sure I can figure out most of this stuff in Excel in a matter of hours!

However, if your time is precious, it seems a quite valuable tool...

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