Performance degradation being caused by a delay in garbage
collection of HTTP session objects.
Download Description
PQ67566 resolves the following problem:
USERS AFFECTED:
WebSphere® Application Server applications that use the session manager
PROBLEM DESCRIPTION:
Performance slowdown is being caused by delay in garbage collection of
session objects.
The session objects after getting timed out are eligible for removal from
the JVM™ by the garbage collection thread. Since the session object
overrides the finalize method, the garbage collection thread takes longer
to perform the removal operation of the session object from the JVM. This
eventually leads to performance degradation.
After getting timed out, the HTTPSession objects are eligible for removal
from the JVM by the garbage collection thread. However, since the
HTTPSession object overrides the finalize method, the garbage collection
thread takes longer to perform the removal operation. This can lead to a
performance degradation because the available memory in the heap decreases
over time, while the frequency of garbage collections increase and the
amount of memory garbage collected decreases. This more frequent garbage
collection causes the performance problem. This fix removes the overridden
finalize method implementation from the HTTPSession object causing it to
be garbage collected much more quickly.
The symptoms of this problem include:
* Frequent Allocation Failures, which causes garbage collection to occur.
* Percentage free after garbage collection (as seen in the verbosegc
output) shrinks over time.
This problem is more likely to occur if the Web application stores large
objects in the HttpSession object. For example, if the application uses
security and stores the authentication token in the HttpSession, this will
increase the size of the HttpSession object, causing it to take up more
space in the heap.
PROBLEM CONCLUSION:
This fix removes the overridden finalize method implementation from the
session object causing it to be removed from the JVM much more
quickly.
Prerequisites
None
Installation instructions
Please refer to the readme detailed for installation
instructions.