Skip emission of internal JFR ThreadPark events

[roberttoyonaga]

When synchronization such as monitor enter or wait is used, Unsafe.park is used under-the-hood to block threads. This results in not only jdk.JavaMonitorWait and jdk.JavaMonitorEnter events being emitted, but secondary jdk.ThreadPark events being emitted as well. The jdk.ThreadPark events are only emitted due to the implementation details of the com.oracle.svm.core.monitor.JavaMonitor and com.oracle.svm.core.monitor.JavaMonitorQueuedSynchronizer classes.

In Hotspot, the Java Unsafe class is not needed to block threads so jdk.JavaMonitorWait and jdk.JavaMonitorEnter events are emitted without corresponding jdk.ThreadPark events.

We should reduce noise and copy Hotspot by skipping the emission of these internal jdk.ThreadPark events.

Hotspot


Notice that there is no jdk.ThreadPark corresponding to the jdk.JavaMonitorEnter event.

Native Image before the fix


Notice that there is a jdk.ThreadPark corresponding to the jdk.JavaMonitorEnter event

Native Image after the fix

[roberttoyonaga]

@christianhaeubl Can you please have a look at this when you have time?