Forum: JRuby [HOWTO] Use Java Mission Control 5.2 with jruby 1.6.x and 1.7.x

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2c0c4cf3ccc8da22f7c3b9586ce1cd70?d=identicon&s=25 Christian MICHON (Guest)
on 2013-10-08 07:57
(Received via mailing list)

If you've installed JDK 7u40, it has Oracle Java Mission Control 5.2
in it. The following HOWTO works only with this JDK, not on a JRE. I've
tested it on Win7 Enterprise, but it should definitely work on linux

JMC (in short) can be used as a monitoring system live (like jvisualvm)
has a more interesting feature, allowing you to monitor and save a
record' even without starting jmc.

In order to do so, please add the following 3 options to JRUBY_OPTS:

-J-XX:+UnlockCommercialFeatures -J-XX:+FlightRecorder

And start the script you wish to monitor. The overhead of creating the
flight record report is supposed to be ~2%. I did not measure it on my
system, but it's definitely low.

For Windows users, you can create such a script to add temporarily the 3
needed options without polluting your JRUBY_OPTS generic settings:
@echo off
set JRUBY_OPTS=-J-XX:+UnlockCommercialFeatures -J-XX:+FlightRecorder
jruby %1

Once the script has completed, in the same directory containing the
script you monitored, you'll get a file like this
one: hotspot-2013_10_08_07_48_58.jfr

Next steps are very simple: start JMC (type 'jmc' on your prompt,
you configured the JDK path properly), then use the JMC menus to open
above mentioned *.jfr file.

You'll get a nice dashboard view, allowing (even days later or on a
different machine) you to monitor the cpu, memory, gc, classes, etc...
metrics saved during that particular run.

Hope this small HOWTO will help you detecting code or memory

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