The VU Activity Chart shows the activity of every VU associated with the load test. It allows visualizing the VU activity and how it relates to other VUs actions. Specifically, it shows which test case and iteration each VU was executing, on which load generator it was emulated and what other VUs were running simultaneously. Because this information is depicted on the timeline, it helps isolate performance issues by seeing how load patterns and test case concurrences correlate with slower test iterations. You can further drill down every test iteration to display a waterfall chart corresponding to this iteration, which displays activity detailed on the level of individual pages and requests.

Info: The VU Activity Chart is available only after the load has finished running.

An example of a VU Activity chart is provided above: 

  • The vertical axle shows VUs (a). 
  • VUs 1-250 were emulated on a controller (b); VUs 251-500 were emulated on the agent (c).
  • Horizontal axle (d) is the timeline. The test duration was a little longer than one hour.
  • During the first 22 minutes, both the controller and the agent were ramping up VUs to the full capacity of 250 VUs each (e). 
  • To zoom-in to a specific VUs/Iterations range, select an appropriate rectangular area (f). 
  • Each VU is depicted by a set of horizontal bars, representing a single test iteration. 
  • The length of a bar indicates how long it took to complete the iteration. Breaks between the bars (g) represent delays after the test cases.
  • The bars are color-coded. Each test case is assigned two unique colors. One of them is used for even iterations (h), and another one is used for odd iterations (i) (alternate coloring). For example, VU 251 and 256 (j) executed the same test case. Also, areas 1, 2, and 3 display how VUs executed the first three iterations at different times.
  • To display details of each test iteration, mouse over its bar. The tooltip (k) will display the following information:
    • VU number
    • Iteration number
    • Iteration start and end time
    • Iteration duration
    • Iteration duration w/o think time.
    • Agent Name
    • Test case name

Generating Test Iteration Waterfall

  • To display a waterfall of an iteration, Dbl-Click its horizontal bar, or right-click (l) and select View Waterfall.
  • You can compare the waterfalls of two iterations. To do so, after selecting the first waterfall, navigate back to VU Activity view and Ctrl+Dbl-Click the second iteration bar, or right-click it (l) and select Compare Waterfalls.

Export iteration data

  • You can export iteration data for every VU. 
  • To export the data points, right-click > select Export to CSV... (g)
  • The following data is exported:
    • VU number
    • Iteration number
    • Test case name
    • Start: the number of ms from the start of the test the iteration started
    • End: the number of ms from the start of the test the iteration ended
    • Duration: the number of seconds End - Start
    • Duration w/o think time: a number of seconds End - Start - think time.
    • Agent Name

Other Commands:

  • To zoom-out, right-click (m), and select Un-Zoom.
  • For additional context menu commands, right-click and select Copy Image, Save Image, or Print Graph Image.

Iteration summary:

When zooming the activity view, the bottom area will show iteration summary information for the zoomed range.

  • Start: the start time of the zoomed range
  • End: the end time of the zoomed range
  • Full iterations: the number of completed iterations in the zoomed range
  • Iterations/sec: the number of completed iterations per second in the zoomed range
  • Avg. Iteration time: the average iteration time (including think time) of the completed iterations in the zoomed range.
  • Partial iterations: the number of iterations that started before the zoomed range and/or ended after the zoomed range.


If the test stopped before an iteration was completed, this iteration would count as a Full iteration if it falls into the entire zoomed range.

Filter by agent

If a load test runs used more than one load agent, then the activity diagram can be filtered to show activity per load agent.

To display the Activity Chart for one load agent, select it from the drop-down in the toolbar. By default, All is selected and displays activity for all load agents.


The iteration summary will also be filtered to show calculations only for the selected load agent when filtering by agent. Also, the export feature will only export the data for the selected.

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