The GCs tab visualizes how and when a garbage collection has occurred during the running of the application (Figure 9-1). It also shows specific information for each garbage collection.
Figure 9-1 The GCs tab
The GCs tab is divided into the following sections:
GCs Overview timeline-this timeline shows the entire recording in its full length (when you initially open your recording). You can use this to refocus the Heap Usage graph, see Changing Focus on GC Chart.
Heap Usage graph-this graph shows heap usage compared to pause times and how that varies during the recording. If you have selected a specific area in the GC Chart, you will only see that section of the recording. You can change the graph content in the Heap Usage drop-down list (marked 6 in Figure 9-1) to get a graphical view of the references and finalizers after each old collection.
Garbage Collections events-this list shows all garbage collection events that have taken place during the recording. When you click on a specific event, you will see a corresponding flag in the Heap Usage graph for that particular event, see Viewing Specifics about Garbage Collections.
Details-this panel contains all the details about the specific garbage collection round. When you select a garbage collection in the Garbage Collection list, the tabs in the Details panel changes depending on if you have selected an old collection or a young collection.
Chart Configuration-this section allows you to change the appearance on the active chart.
Drop-down list and Show strategy changes-the drop-down list allows you to select one of these views on the Heap Usage chart:
Heap Usage
References and finalizers
Pause Time
CPU
If you select Show strategy changes, you will see when JRockit has changed garbage collection strategy.
Move and Zoom buttons-these buttons are used with the GCs Timeline.
