Probe Hot Spot Comparison


  The probe hot spot comparison is one of the probes comparisons. It is created by invoking the probes comparison wizard. For more information on snapshot comparisons, please see the snapshot comparison overview.
  The wizard has the following additional steps:
  • Select snapshots
    The probe hot spots comparison compares two snapshot files. In this step, you select the first and the second snapshot file for the comparison. The combo boxes contain all snapshot files that have been added to the snapshot selector. You can use the same snapshot file for the first and second snapshot file, in which case the thread selections in the next step must be different.
  • Probe selection
    In this step, you choose for which probe the comparison should be made. If you select the "custom probe" option, all snapshots are analyzed to find out which custom probe are present in all snapshots.
  • Thread selection
    In this step, you choose for which threads the comparison should be made. By default all threads are selected, you can restrict the thread selection to single thread groups or single threads.
  • View parameters
    In this steps you can select thread status and aggregation level, just as for the probe hot spots view. In addition, you can choose whether to calculate differences of total call times or of average call times (total time divided by invocation count).
  Each row in the probe hot spot comparison has the following columns:
  • the name of the payload hot spot
  • the self time in the second snapshot file minus the self time in the first snapshot file
  • the invocations in the second snapshot file minus the invocations in the first snapshot file
The second column incorporates a bidirectional bar chart. Increases are painted in red and to the right, while decreases are painted in green and to the left. In the view settings dialog you can choose whether you want this bar chart to display absolute changes or the percentage of the change. The other value is displayed in parentheses. This setting also determines how this column is sorted.
  By default, only payload hot spots that have changed from one snapshot file to the other are displayed. You can change this behavior in the view settings dialog.
  At the bottom of the probe hot spot comparison is a view filter selector that filters data for specific package or class names.