Setting up event-based sampling

The default behavior of Streamline is to capture data samples based on a regular time step. Alternatively, event-based sampling (EBS) enables you to take samples when a user-defined counter reaches a threshold value. For example, triggering data samples for every 100,000 level two cache misses.

About this task

  • Only CPU hardware counters and counters that are in the category Perf Software support EBS.

  • EBS is only possible when the PMU on the target hardware can generate interrupts.

Procedure

  1. In the Start view, select the Use advanced mode checkbox.

  2. Click Select Counters.

  3. Click Toggle event-based sampling toggle_ebs for an event in the Events to collect list.

    Event-based sampling is active for all matching events.

    If Toggle event-based sampling toggle_ebs is not displayed next to an event, then that event does not support event-based sampling.

  4. Enter a value in the Threshold field.

    Avoid setting a very low threshold for high frequency events, because it might cause a capture to fail. If you enter a threshold value that generates too many samples, the capture could fail, and you might have to restart your target. Your target for the Threshold field should be to generate 1000 samples per second. Therefore, if your application typically generates two million counter increments per second, a good value to insert in the Threshold field is 2000.

    Setting up event-based sampling