WLS not garbage collecting enough?

Question

WLS 5.1 SP5
SunOS 5.6 (2.6)
JDK 1.2.2_005a (with the JVMARGS directive set as per BEA's docs. The
JVMARGS directive solved the SIGBUS 10 for us when requesting the
AdminMain servlet)
We tried some stress testing of our web app by running about 100 to 200
virtual clients requesting the same URL (servlet that forwards to a
JSP). These virtual clients are actually Java threads running
simultaneously.
After each test, we notice that, via WL console, the heap usage of WL
increased. However, after leaving WL server by itself (no HTTP requests
coming to it) for a long time (say 30 minutes to 1 hour), we noticed
that the heap usage has not gone down, except for about 1%. As soon as
we explicitly tell WLS to garbage collect via the WL console, then the
heap usage goes down ... sometimes even as low as just 10% when we tell
it to gc again just after a gc a few seconds earlier.
Is this proper behaviour by WLS? ... or does this have something to do
with the JVMARGS directive? Why doesn't it gc even after a long time?
Thanks in advance,
John Salvo
Homepage: http://homepages.tig.com.au/~jmsalvo/

Answer 1

There are a number of problems with memory usage and garbage collection. Going to WLS 5.1 will fix
some of them. You should also consider having your application call System.runFinalization(); and
System.gc() from time to time.
Mike
"Jim Zhou" <[email protected]> wrote:
I see the same behavior in my stress test/pre-production run. I think it's
normal behavior. The GC will kick in when the heap size gets 100%, you might
see a pause in your WLS because all threads will stop for the GC ( you
should see CPU really busy when GC is in ). JDK 1.2 should have better GC
algorithm than JDK 1.1. Usually for people still using JDK1.1.x, tuning the
heap size for tolerable GC pause is a pain., the tuning guide want you to
run multiple WLS instances in a box to stagger the effects of GC pause. If
you use JDK 1.2, you probably set your heap size comparable to your box's
memory.
In one of my stress test, I set heap size to 256m, I see on my console the
heap gets full every 30 seconds, and it take 1 or 2 seconds to GC. But if
your heap is 2G, it might take longer.
WLS 4.51 SP11
Solaris 2.6
JDK 1.2.2_06.
Regards,
Jim Zhou.
Jesus M. Salvo Jr. <[email protected]> wrote in message
news:[email protected]...
WLS 5.1 SP5
SunOS 5.6 (2.6)
JDK 1.2.2_005a (with the JVMARGS directive set as per BEA's docs. The
JVMARGS directive solved the SIGBUS 10 for us when requesting the
AdminMain servlet)
We tried some stress testing of our web app by running about 100 to 200
virtual clients requesting the same URL (servlet that forwards to a
JSP). These virtual clients are actually Java threads running
simultaneously.
After each test, we notice that, via WL console, the heap usage of WL
increased. However, after leaving WL server by itself (no HTTP requests
coming to it) for a long time (say 30 minutes to 1 hour), we noticed
that the heap usage has not gone down, except for about 1%. As soon as
we explicitly tell WLS to garbage collect via the WL console, then the
heap usage goes down ... sometimes even as low as just 10% when we tell
it to gc again just after a gc a few seconds earlier.
Is this proper behaviour by WLS? ... or does this have something to do
with the JVMARGS directive? Why doesn't it gc even after a long time?
Thanks in advance,
John Salvo
Homepage: http://homepages.tig.com.au/~jmsalvo/