Retrieving "Method Profiling Sample" event duration

Question

Hello,
I am trying to understand how JMC calculates the Percentage in Hot Methods (which according to documentation is total time that the application spent on executing code in the method), but the duration I retrieve seem to be always zero and start and end timestamps are the same. The way I am trying to do it follow below:
FlightRecording recording = FlightRecordingLoader.loadFile(new File("jfr file path"));    
IView view = recording.createView();
Map <String, IEventType> eventTypes =  new HashMap<String, IEventType>();
for (IEvent event : view) {
     eventTypes.put(event.getEventType().getName(), event.getEventType());
view.setEventTypes(Arrays.asList(eventTypes.get("Method Profiling Sample")));
for (IEvent event : view) {
     System.out.println(event.getValue("(duration)") + " " + ((FLRMethod)event.getValue("((stackTrace).method)")).getMethodName());
Any clarification is highly appreciated!
Thanks in advance.

Answer 1

The Method Profiling Samples do not have a duration,
they are taken at interval of for example 20 ms, where a predefined number of threads are sampled.
All threads cannot be sampled, for example the ones that are executing native code.
It's really "the percentage of the total  number of samples that were taken in this method", which can be seen as an approximation of what the help says "The percentage of total time that the application spent on executing code in the method."
To get this we group together all the samples with the same top frame, there is not one single sample for each method with a total duration for that method.
If you look at the Events/Log, and only enable Java Virtual Machine/Profiling/Method Profiling Sample in the event types view, you will be able to see what kind of data you get.