Considerations When Comparing Lock Contention and Thread Histogram Metrics:

Lock contention data is sampled less frequently than thread histogram data. When there is lock contention with a short lifespan, a small amount of lock contention might appear in the Thread Histogram, but not be shown in the Lock Contention percentages. This can happen when the contention occurs during a time when the Thread Histogram sample is being taken, but the lock contention sample is not.

Related Topics

•Thread Histogram (page 131)

•Identifying Excessive Lock Contention (page 45)

•Identifying Deadlocked Threads (page 45)

•Data Sampling Considerations (page 188)

Monitor JVM and/or System Activity Menu

Method Compilation Count

Displays a list of all the methods compiled from the time the session was opened, showing the number of times a particular method was compiled.

The metric window reports “No methods compiled since the session opened.” until the next method compilation occurs, and then the metric data appears.

Guidelines

•The normal values for this metric are single-digit numbers.

•If the top item or items show a much larger value than the rest of entries, and the value constantly grows, it suggests excessive method compilation.

•Normally, a method is compiled once or just a few times, which results in a very flat profile, with none of the entries showing large numbers.

However, a JVM may have a performance problem in which a certain method, or methods, is compiled repeatedly. Such a problem manifests itself in one entry clearly dominating the list and showing constant growth over time.

Figure 8-15 Monitoring Metric: Method Compilation Count

134 Using Visualizer Functions