Profiling Telemetry

This page describes the Telemetry profiling mode.


When running in Telemetry mode (see First Profiling Session for details on starting a profiling session) the profiler just monitors the target application with a very low overhead. Telemetry mode is the ideal profiling mode to take a Thread Dump or Heap Dump from the profiled application. Also the garbage collection in the target VM can be requested using a toolbar button. The profiling session is started by simply clicking the Profile or Attach button in toolbar. The other toolbar buttons are described in the Toolbar Buttons section.

Toolbar Buttons

  • View group contains toggles for showing or hiding CPU and GC, Memory, Garbage Collection and Threads and Classes graphs. See the Telemetry Graphs section for more information about the graphs.
  • Take thread dump action takes snapshot of all threads in the profiled JVM including their call stacks and displays it in a separate view. See the Thread Dump chapter for details.
  • Take heap dump action saves a snapshot of all objects currently stored in the heap memory in a .hprof format and optionally opens it in a heap viewer. See the Heap Dump chapter for details.
  • Request garbage collection action requests garbage collection in the profiled JVM. There's no guarantee when or if at all the garbage collection will be performed. To make sure GC will be run, the action should be invoked several times.

Telemetry Graphs

  • CPU and GC graph displays the actual CPU utilization by the application and relative overhead of garbage collection.
  • Memory graph displays the actual heap size and usage, also shows the heap limit.
  • Garbage Collection graph displays the estimated number of different surviving generations in the JVM and intervals where the garbage collection has been performed.
  • Threads and Classes graph displays number of live threads and loaded classes in the JVM.

Each graph displays the full data for a profiling session and can be zoomed and panned separately by the control buttons and mouse wheel (see the tooltips). A graph can be maximized to display more details by hiding the other graphs using the toolbar buttons.

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