Performance meter in weblogic console

Question

All,
Semi new to memory analysis on the server side (distributed garbage
collection and all). I was rather used to doing client application memory
leak analysis. Are there any good starter guides for memory analysis when
doing load testing?
I am currently working on a project where we do severe load testing against
servlets that hit session level EJB and then entity EJB. We see the heap
(Server->monitor->performace) sawtooth slowly up until the server throws out
of memory exceptions and starts to fail. We have already fixed a few
glaring problems with our code, but the sawtooth remains.
What is the garbage collection routine under WebLogic? Does it run
periodically? Does it run during high/low activity? Should it not be
called before any OutOfMemory exception is throw?
If you set the ejb's to keep too many ejb references in the cache, will the
server sanity check this and bump some out of the cache when memory gets
tight? Basically, I'm asking could I shoot myself in the foot in
weblogic-ejb-jar.xml or will the server help me out?
Finally, if you start mydomain as shipped and go to the performance graph it
slowly sawtooths up at a very slow pace. If you let it run over night it
eats up 10 megs or so. Why is this? It looks rather bad, but I can't
assume this is as it looks on the surface.
Sorry for all the questions, but maybe this will start a good thread.
Andrew Spyker ([email protected])
Software Engineer
http://spyker.dyndns.org

Answer 1

JVM heap usage will grow and shrink throughout the life of the server. Even an
idle WebLogic server is allocating and freeing object instances. Therefore,
when looking for a "leak", make sure that you account for the state of the JVM
garbage collection and compare "apples" to "apples".
I find that it is best to compare the heap usage after full garbage collections
(GC[1]). Try enabling -verbose:gc and comparing each of the full GC results.
Provided that your server is handling a constant and steady load (or is
constantly idle), you should see little change in heap usage after each full
GC. However, if your your server is idle you may need to force GC to run every
hour or so. By default, you need to use nearly all of the allocated heap
before full GC will kick in.
-Charlie
Andrew Spyker wrote:
"Mike Reiche" <[email protected]> wrote in message
news:[email protected]...
The garbage collector is a function of the JVM, not of WebLogic. Look atthe JVM
documentation for an explanation of garbage collection.Gotcha.
Weblogic, without any application code runs fine. When you add YOURapplication
code, then you might run into problems. Hence it is your code that ischewing
up (and not releasing) the memory. JProbe is good at find this kind ofproblem.
You can also narrow things down - for instance - hit only one servlet andsee
if the memory grows. Or remove references to session beans, and hit theservlet.
I should be more specific. I installed WLS SP2 on Redhat Linux 7.1 and ran
startWeblogic.sh from the default mydomain. I didn't make any
modifications. I ran the performance meter and the memory did grow over
night significantly. This suprised me. Do I attribute this to Linux? Our
production environment is definately Solaris, but I'd like to be able to
diagnose memory leaks on Linux. I don't want this false positive in the
tests. Am I missing something here?
OutOfMemoryExceptions occur when the JVM attempts to allocate more memorythan
is available - even after running garbage collection. The JVMoption -verbose:gc
will also shed some light on GC.
The Java Heap is not the only part of the JVM that requires memory. Inrare cases,
much memory is consumed by classes and methods in memory, heap (not javaheap)
used by native code.
Mike ReicheThanks for the response ...
"Cameron Purdy" <[email protected]> wrote:
It is not easy. Optimizit and JProbe can help, as can a well-architected
application with classes that support dumping debugging information (to
evaluate object graphs) and serialization (to guage sizes).
Typical leaks are in session objects, static fields, and database driver
usage without proper closing of objects.
Peace,
Cameron Purdy
Tangosol Inc.
<< Tangosol Server: How Weblogic applications are customized >>
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"Andrew Spyker" <[email protected]> wrote in message
news:[email protected]...
All,
Semi new to memory analysis on the server side (distributed garbage
collection and all). I was rather used to doing client applicationmemory
leak analysis. Are there any good starter guides for memory analysiswhen
doing load testing?
I am currently working on a project where we do severe load testingagainst
servlets that hit session level EJB and then entity EJB. We see theheap
(Server->monitor->performace) sawtooth slowly up until the server
throws
out
of memory exceptions and starts to fail. We have already fixed a few
glaring problems with our code, but the sawtooth remains.
What is the garbage collection routine under WebLogic? Does it run
periodically? Does it run during high/low activity? Should it notbe
called before any OutOfMemory exception is throw?
If you set the ejb's to keep too many ejb references in the cache,will
the
server sanity check this and bump some out of the cache when memorygets
tight? Basically, I'm asking could I shoot myself in the foot in
weblogic-ejb-jar.xml or will the server help me out?
Finally, if you start mydomain as shipped and go to the performancegraph
it
slowly sawtooths up at a very slow pace. If you let it run over nightit
eats up 10 megs or so. Why is this? It looks rather bad, but I can't
assume this is as it looks on the surface.
Sorry for all the questions, but maybe this will start a good thread.
Andrew Spyker ([email protected])
Software Engineer
http://spyker.dyndns.org