HPjmeter 4.2 User's Guide

Figure 6-2 Summary Panel Showing Garbage Collection Statistics
Heap Capacity Initial, final, and peak sizes allocated for various organizational spaces in
the heap.
Peak Usage of Capacity The highest percentage of actual use by the application of the heap
at its final capacity configuration. A rule of thumb for optimal utilization would be to have the
eden space at 100% with the survivor and old spaces showing some reserve capacity, depending
on the application.
GC Activity Summary In this example, a comparison of scavenges and full garbage collection
of the old and permanent generations, showing number of GC occurrences, duration, and memory
usage for each GC type displayed.
Duration of the Measurement The approximate, elapsed, wall clock time for the entire data
collection.
Measurement Enabled and Measurement Disabled “Measurement enabled” refers to the total
time during which zero preparation GC data collection has been activated during the session
thus far. “Measurement disabled” refers to the total time during which no data was collected
(zero preparation GC data collection is not in use). These values are visible on this tab when zero
Basic Garbage Collection Concepts 89