PQ67566, 4.0.2, 4.0.3, 4.0.4: GarbageCollection causes performance degradation
 Downloadable files
 
Abstract
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.
 
URL LANGUAGE SIZE(Bytes)
Readme US English 3060
 
Download package
What is DD?
DOWNLOAD RELEASE DATE LANGUAGE SIZE(Bytes) Download Options
PQ67566 - 4.0.2 10/24/2002 US English 869330 FTP DD
PQ67566 - 4.0.3 10/24/2002 US English 869330 FTP DD
PQ67566 - 4.0.4 10/24/2002 US English 869379 FTP DD
 
Technical support
1-800-426- 7378 U.S. Only
 
Problems (APARs) fixed
PQ67566
 
 


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server > Servlet Engine/Web Container
Operating system(s): Linux
Software version: 4.0.4
Software edition:
Reference #: 4001902
IBM Group: Software Group
Modified date: Jun 1, 2004