JVM statistics are displayed through the Admin Console, the CLI, and stats-xml only. They are not shown in perfdump.
The following table shows an example of the JVM statistics displayed in the Admin Console:
Table 2–7 Java Virtual Machine (JVM) Statistics
Virtual Machine Name |
Java HotSpotTM Server VM |
Virtual Machine Vendor |
Sun Microsystems Inc. |
Virtual Machine Version |
1.5.0_06-b05 |
Heap Memory Size |
5884856 |
Elapsed Garbage Collection Time (milli seconds) |
51 |
Present Number of Classes Loaded |
1795 |
Total Number of Classes Loaded |
1795 |
Total Number of Classes Unloaded |
0 |
Number of Garbage Collections Occurred |
3 |
Number of Live Threads |
8 |
Number of Started Threads |
9 |
Peak Live Thread Count |
8 |
Most of these statistics are not tunable. They provide information about the JVM's operation.
Another source of tuning information on the JVM is the package java.lang.management, which provides the management interface for monitoring and management of the JVM. For more information on this package, see http://java.sun.com/j2se/1.5.0/docs/api/java/lang/management/package-summary.html.
As with all Java programs, the performance of the web applications in the Web Server is dependent on the heap management performed by the JVM. Balancing times and throughput is a challenge. For more information, read the performance documentation for the Java HotSpot virtual machine, which can be found at http://java.sun.com/docs/hotspot/index.html.
Specific documents of interest include “Tuning Garbage Collection with the 5.0 Java Virtual Machine” and “Ergonomics in the 5.0 Java Virtual Machine”.
JVM options can be specified in the Admin Console on the configuration's Java tab ⇒ JVM Settings sub tab. In the CLI, use the wadm commands set-jvm-prop and set-jvm-profiler-prop.