TIP: To best view the relative amount of starvation for a particular thread, highlight the thread by clicking on it once, or double-click to reveal the thread pie chart for that thread. Starvation is represented by the “empty” slice of the pie.

NOTE: Be careful when analyzing the spectrum of a thread group. A thread group may contain several threads with completely different roles within the application. Mixing them up and analyzing just the summary may make little sense. User-defined thread groups that contain only carefully selected threads (usually sharing the same code) are well suited for spectrum analysis.

See also Thread Histogram (page 131)

Using Call Graph Trees

The call graph trees are used to represent metrics based on graphs. There are four metrics based on the method call graph (showing CPU Time, Clock Time, Call Count, and Lock Delay), and two based on object references (Reference Graph and Reference Sub-Trees by Size).

You can expand or collapse any non-leaf node by clicking on the small square on the left side of each node.

A consequence of representing a graph in the tree form is that the same graph node can be displayed many times within the tree (showing different paths in the graph). Special color coding of the nodes helps you to navigate the tree. Five colors are used:

Table 5-6 Key to Color Coding of Call Graph Nodes

Leaf. Leaf nodes, written in black, represent methods that did not call any other methods or objects that do not keep any references to other objects. Leaf nodes cannot be expanded or collapsed.

Expanded. After expansion the node will be shown using gray.

Expanded Elsewhere. A tree node that is already expanded elsewhere in the tree will be shown in red.

It is possible to expand this node if you want to do so. The information shown will be identical to that already displayed where the node is expanded. You may find that expanding the same graph node in more than one place makes the tree less manageable.

Visited. A node that you have expanded and then collapsed is called a visited node. It is shown in a different color (purple) to remind you that you have already looked at the contents of this node.

Regular. All other non-leaf nodes that have not been visited are presented in blue.

See the figure below for examples.

Interpreting Call Graph Data

In the trees that are based on the call graph, the nodes represent methods and the arcs represent cumulative calls from the preceding node.

•For CPU and Clock trees, the numerical values represent the time used by the arc. That is, the numerical values represent the inclusive time used by all invocations represented by the arc. The numbers in parentheses indicate what percentage of the total inclusive time used by the method was caused by the calls from the preceding node. By default, the arcs with numerical values less than 50 are not shown.

•For a Call Count tree, the numerical values represent the number of calls made to the method from the preceding node (the caller). The percentage numbers represent the ratio of calls

Using Call Graph Trees 75