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2. View or adjust the Maximum Heap Size and set the Initial Heap Size to the same value.
3. Stop and re-start the application.
Enabling the JIT compiler
When a JVM JIT (Just-In-Time) compiler is present and enabled, the Java Virtual Machine performs differently. After
reading in a .class file for interpretation, the JVM hands the .class file to the JIT. The JIT takes the bytecodes and
compiles them into native code for the machine that you are running on. Using this technique it can actually be
faster performance-wise for the JIT to obtain the bytecodes, compile them “on the fly,” and run the resulting
executable rather than just interpreting it. The JIT compiler is then an important part of the Java Virtual Machine in
that it can allow Java code to run faster.
The WebSphere Administrative Console lets you either enable or disable the JIT. To do this in the WebSphere
Administrative Console, use the following procedure. Do this for both the Learning Server and Delivery Server
applications.
1. Select Application Servers – <server name> - Process Definition - Java Virtual Machine
2. Make sure that the JIT compiler setting is set to Enabled
3. Stop and re-start the application.
Adjusting the JVM parameter to avoid class verification
The JVM parameter lets you skip the class verification stage during class loading, saving you overhead. When using
this value with the JIT on, gains are between 10–15 percent in startup time.
To view or change this parameter, use the following procedure:
1. In the WebSphere Administrative Console, go to Application Servers - <server_name> - Process Definition -
Java Virtual Machine.
2. Add the value “-Xverify:none” to the Generic JVM arguments field.
Adjusting the JVM parameter garbage collection threads
The JVM parameter lets you set the number of garbage collection threads to save on overhead. You can have several
garbage collection threads. If you machines have more than one processor, set the number of threads equal to the
number of processors. This is only applicable for IBM JDK 1.3.
To view or change this parameter, use the following procedure:
1. In the WebSphere Administrative Console, go to Application Servers - <server_name> - Process Definition -
Java Virtual Machine.
2. Add the value “-Xgcthreads=[number_of_processors]” to the Generic JVM arguments field.
Adjusting the Web container thread pool
A thread pool enables components of the server to reuse threads to eliminate the need to create new threads at run
time. Requests are sent to the server through any of the HTTP transports. Creating new threads expends time and
resources.
In WebSphere, there are 2 parameters that can be changed to adjust the Web Container thread pool size:
• Minimum size – Specifies the minimum number of threads to allow in the pool. This value should be left to
its default value of 10.
116 IBM Lotus LMS Release 1 Installation Guide