Related Topics

•Unfinalized Queue Growth (page 115)

•Thread Histogram (page 131)

•Reading Profiling Histograms (page 73)

•Profiling with -Xeprof (page 61)

Allocated Object Statistics by Class

Shows object allocation statistics according to the object type allocated.

Guidelines

A typical large Java application allocates a lot of strings. This value can reach 25 percent of all allocations. If any other type, especially an application-defined type approaches or exceeds such a value, it may indicate inefficient code.

Details

For those classes that are instrumented (visible through the JVM agent verbose flag), every object allocation in every method is instrumented to report allocations. However, sampling is used to minimize overhead, so the metric reports allocation percentages, not total allocation counts. These percentages are not absolute across the entire application, but are computed with respect to allocations in instrumented classes.

Sampling minimizes overhead and focuses attention on user code. To discover allocation statistics about application server classes, use the include and exclude filtering flags in the JVM agent options.

The reported data is cumulative over the lifetime of the session, and accuracy will improve as the session length increases.

Using Monitoring Displays 127