Java Mission Control Heap Profile
I am playing with the new Java Mission Control Profiler that is coming with the Java 7u40 and I cannot make it to profile allocation and collect object statistics. No matter what I do, I cannot see any statistics in the Memory -> Object Statistics window.
The following command starts the collection:
jcmd <pid> JFR.start duration=60s settings=profile filename=alloc-prof.jfr
The Java Mission Control documentation does not mention any specific options to enable object profiling. I have tried to create my own profile and set :
<flag name="heap-statistics-enabled" label="Heap Statistics">true</flag>
<flag name="allocation-profiling-enabled" label="Allocation Profiling">true</flag>
But still no Object Statistics are collected.
Answer
Use the template manager that is available in Mission Control.
Go to Windows -> Template Manager and import the template and check Heap Statistics and Allocation Profiling, export it. Done!
If you want to edit the jfc-file manually, it can be good to know elements inside the control-element are not read by the JVM, i.e flag-element, They are used by JMC to modify the parameters outside the control element (the one with the control attribute)
A manual edit requires that you modify these:
set java/object_alloc_in_new_TLAB enabled to true
set java/object_alloc_outside_TLAB enabled to true
set vm/gc/detailed/object_count enabled to true
Note, there are two object count events, with object_count_after_gc you will increase GC times. If you pick the one above instead, you will get one additional GC per recording chunk (which is usually sufficient)