VM Telemetry Comparisons Overview

All telemetry snapshot comparisons are created by invoking the telemetry comparison wizard. For more information on snapshot comparisons, please see the snapshot comparison overview.

The wizard has the following steps:

Choose comparison type
In the first step of the telemetry comparison wizard, you select the desired comparison type, which compares values from the corresponding VM telemetry view:
- Heap comparison
- Recorded objects comparison
- Classes comparison
- Threads comparison
Select snapshots
The telemetry comparisons compare two or more snapshot files. In this step, you select whether you want to compare the snapshots that you have selected in the snapshot selector, or whether all snapshot files should be compared. The default selection depends on whether you have selected more than one snapshot in the snapshot selector.
Memory type

This screen is only shown for the "Heap comparison" and lets you choose a memory pool for comparison as explained on the help page of the VM telemetry views. Only memory pools are shown that are contained in all compared snapshots.
Comparison type
Each snapshot file contributes one value to the comparison graph. That value can be the
- current value
  This is the value when the snapshot was saved, i.e. the rightmost point in the telemetry view and the value that is displayed next to the legend entries there.
- maximum value
  This is the maximum value during the entire time that the telemetry view was recording data. The maximum value is evaluated separately for each snapshot file.
- value at a bookmark
  In JProfiler, you can set bookmarks for specific points in time. In addition, there are automatic bookmarks for recording events. If all compared snapshots contain a bookmark with the same name, you can compare values at those times. If you choose this option you have to select a bookmark from the combo box below. Only bookmarks that are contained in all snapshots are displayed.
Compared measurements
In this step you select which of the measurements from the corresponding VM telemetry view should be compared. You can select any combination of measurements, for each telemetry comparison there's one preferred measurement that's compared by default. The available measurements are:
- Heap comparison
  Maximum, free and used heap size (default)
- Recorded objects comparison
  Total number of objects (default), non-arrays, arrays
- Classes comparison
  Total number of classes (default), profiled classes, unprofiled classes
- Threads comparison
  Total number of threads (default), inactive threads, active threads

Any telemetry comparison behaves similarly to the VM telemetry views themselves, on the horizontal axis you see the snapshot numbers from the snapshot selector, the vertical axis remains the same. Effectively, the time axis from the VM telemetry views is replaced by an ordinal snapshot file axis.

There are several view settings that influence the display of the comparison. Please see the help on the VM telemetry views for more information.