The visualgc tool is related to the jstat tool, see The jstat Utility. The visualgc tool provides a graphical view of the garbage collection (GC) system. As with jstat, it uses the built-in instrumentation of the Java HotSpot VM.
The visualgc tool is not included in the JDK release but is available as a separate download from the jvmstat technology page.
Figure 2-16 demonstrates how the GC and heap are visualized.
