HPjmeter 4.3 User's Guide

Guidelines

• For a healthy heap, minor collections should dominate major garbage collections. If the number

of minor collections is too small compared to the number of major garbage collections, the

young generation of the heap may be too small.

• If the heap size shown by garbage collections converges towards the heap limit, the application

has run out of memory, or soon will run out.

• If the old generation is too small, the application will run out of memory. If the total heap size

is too large compared to available physical memory, thrashing occurs.

• A value of 5 percent or less of time spent in garbage collection is acceptable. Values larger

than 10 percent usually indicate an opportunity for improvement.

• With a time span of more than one hour, you can identify possible memory leaks. See

Determining the Severity of a Memory Leak (page 53).

Details

Each point on the graph represents the heap size after a garbage collection completes; it represents

the amount of live memory at that time.

Frequent long garbage collections represent a potential problem, and will be coupled with a high

percentage of time spent in garbage collection. This percentage is displayed in the lower right of

the window.