The Communication Flow graph offers a quick overview of the communication and synchronization between actors in a trace, through message queues, semaphores and mutexes.

This graph can be generated over a whole trace, or for a specific interval only. For example, you might use the CPU Load Graph view to identify a peak where there is a lot of activity, then select that peak using a mouse drag selection, right click and select "Show Communication Flow" in the context menu to show the communication flow graph of that specific interval.

Actors are shown as rectangles, and other objects are shown as ellipses or hexagons. Ellipses are used for directional communication and synchronization objects, while hexagons are used for bi-directional objects like Mutexes and similar.

Double-clicking on any node opens a related view that displays all matching events, such as the Object History view.

There are two modes in this view:

• Actors and Objects: Shows all objects and dependencies, both actor communication and dependencies on synchronization objects, like Mutexes.
• Actors Only: In this mode, only those actors are shown which have communication dependencies to other tasks. Dependencies on bi-directional objects (e.g. Mutexes) are not shown.

The classification of objects into directional objects (ellipses) and bi-directional objects (hexagons) are based partially on the static type of the object, partially on the service calls found referencing the object. This since semaphores can be used for both purposes, as a directional signal (a form of communication), and as a synchronization lock, i.e., like a Mutex. A object is treated as a synchronization object (hexagon) if there are actors that both increment and decrement the object state (e.g., do both a "LockMutex" and "ReleaseMutex"). This means that a semaphore can show up as a hexagon (if one actor both signals and waits for it) while a mutex in rare cases might show up as an ellipse, if only one type of operation ("LockMutex" or "ReleaseMutex") is recorded on the particular object.

Applying Filters

Sometimes it's useful to filter out specific tasks or objects, such as if you have a debug or log writer task that many other tasks send data to. By default, all actors and objects that do not perform any communication are hidden, but you can adjust these settings using View -> Select Objects.... You can also right-click a node to hide it.

When right-clicking a node, you'll also be presented with options to show only connected nodes, in one, two or unlimited steps. This shows only actors and objects that affect or are affected by the selected actor or object via directed communication (undirected communication such as through mutexes are not followed even though the objects will be displayed).

The Show All Connected and the Show All Connected Only options will show the same nodes (actors/objects) but might show different sets of edges (lines). The difference is that the former does not hide communication between those nodes even if it's unrelated to the selected node. For example, if you have the communication chains taskA -> queueB -> taskB -> outputQueue and taskA -> outputQueue and you show nodes connected to taskB, Show All Connected Only (2 steps) would show only the first chain while Show All Connected (2 steps) would also show the second chain.