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Actor Instance Graphs

Overview

The Actor Instance Graph window displays a graph showing timing properties of actor instances: execution time, response time, response interference and fragmentation. Each data point in the graph represents a specific actor instance, where the x-axis shows the instance start time and the y-axis the property value.

Clicking a plotted instance will show and highlight it in the trace view. You can filter actors using the Filter menu or by clicking on an actor in the legend to the right.

If you wish to focus on a specific area, you can click and drag to select an interval and use the Zoom menu or right click to zoom in on it. You can also use the Zoom or right click menu to show the selection or current view in the trace view or in all open views.

This view can be used to identify long-running tasks using the execution and response time graphs, or potential scheduling problems using the fragmentation and interference graphs.

The properties that can be plotted are:

  • Execution Time: The amount of CPU time used by an Actor Instance, excluding preemptions.
  • Response Time: The time from the start of an actor instance until it finishes. The response time for tasks is counted from the point when the task becomes ready to execute (i.e., the point where the kernel sets the task's scheduling status to READY). For Interrupt Service Routines, the Response Time is counted from start of execution. Note that READY events can be excluded to reduce RAM buffer usage. In such cases, Task Response Time is counted from start of execution.
  • Wait Time: This is Response Time - Execution Time, i.e., the time within an instance when the actor is not executing.
  • Startup Time: This is the time between ready and execution start.
  • Response Interference: The relation between execution time and response time. A value of 30% means that the response time is 30% longer than the execution time, i.e., due to preempting tasks, interrupts or blocking. A value of 0% means that the response time is equal to the execution time, i.e., that the actor instance executed to completion without context switches.
  • Fragmentation: The number of fragments within an Actor Instance, i.e., due to context switching. If an Actor Instance executes in full without preemptions, the fragmentation of the instance is 1.
  • Separation: The time between the instance start time and the previous instance finish. Available in two versions, depending on where to count the instance start time: from Ready and from Execution Start.
  • Periodicity: The time between the instance start time and the previous instance start time. Available in two versions, depending on where to count the instance start time: from Ready and from Execution Start.

You can combine this view with other horizontal views by choosing Views -> Add -> (graph type).


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