In the latest podcast, Tor mentions jconsole as having a cut-down
version of the NetBeans profiler in it.
This is incorrect. VisualVM has this, jconsole does not. He is correct
in stating that this ships with the Sun's Java 6 JDK, however -- just
don't look for it in jconsole. Last I checked it contained more "real
world" capability than NetBeans itself as NetBeans wouldn't let you do
completely sampling-based CPU profiling (low fidelity, low overhead to
figure out what portions of the app to instrument for detailed
profiling) on anything other than itself! VisualVM will, as well as
instrumentation-based CPU profiling and memory profiling. [I have to
say that MAT, i.e. http://www.eclipse.org/mat/, is in a class by itself
for many memory usage examination situations, though.]
Overall, the only point to jconsole in Java 6 is on AIX, where VisualVM
is not only not delivered with the IBM JVM (the only JVM on AIX), but it
won't even run on it. Otherwise just add the jconsole related plug-ins
to VisualVM as these plugins fix serious usability issues in the
jconsole UI (e.g. the horrible placement of Attributes, Operations, etc,
as alphabetically placed child nodes in the MBean tree rather than as
tabs in the details page as in Java 5) and VisualVM gives you a lot more
capability overall.
Having written a jconsole plug-in, however, I can say that this is a
nice, simple approach for a simple plug-in that can be used with either
jconsole or VisualVM. The alternative is to write a VisualVM plug-in,
which gives you much more power to extend the VisualVM UI, but only
works in VisualVM and is much more involved than the jconsole plug-in
API (which could hardly be simpler).
As for Mission Control, my high-level understanding is that JRockit has
more detailed yet high-performance/low-overhead internal instrumentation
in some areas than Sun's JVM. Certainly Sun's JVM is really poor on
live GC instrumentation apart from parsing GC logs (yuck!), e.g. the JMX
APIs in this area are *extremely* limited. I'm sure there are other
areas like this, but GC sticks out like a sore thumb.
--
Jess Holle
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