RFR: JDK-8298255: JFR provide information about dynamization of number of compiler threads

[Matthias Baesken]

On Wed, 7 Dec 2022 15:32:18 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> The JVM supports both dynamic GC threads, and dynamic Compiler threads.
> While the GCConfiguration JFR event (see https://sap.github.io/SapMachine/jfrevents/#gcconfiguration ) seems to have at least some info about dynamization of GC threads ( field usesDynamicGCThreads), the JIT CompilerConfiguration event seems to miss this info (about JIT compiler threads dynamization), this should be added; currently the impression is given that the number is static but this is often not the case.
> As an extension, the dynamization process of adding / removing threads could be added as well to the JFR events but I am not sure if this is desired so I just started with a very simple patch.

Hi Markus and Thomas,  unfortunately I learned that the event field names must not be longer than 32 chars.
Otherwise  test  jdk/jfr/event/metadata/TestEventMetadata.java  fails with 

java.lang.RuntimeException: Name should not exceed 32 characters: expected true, was false
	at jdk.test.lib.Asserts.fail(Asserts.java:594)
	at jdk.test.lib.Asserts.assertTrue(Asserts.java:486)
	at jdk.jfr.event.metadata.TestEventMetadata.verifyName(TestEventMetadata.java:149)
	at jdk.jfr.event.metadata.TestEventMetadata.verifyValueDescriptor(TestEventMetadata.java:130)
	at jdk.jfr.event.metadata.TestEventMetadata.verifyValueDesscriptors(TestEventMetadata.java:125)
	at jdk.jfr.event.metadata.TestEventMetadata.main(TestEventMetadata.java:101)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
	at java.base/java.lang.reflect.Method.invoke(Method.java:578)
	at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:125)
	at java.base/java.lang.Thread.run(Thread.java:1623)

So I shortened the field name (and fixed a test typo while at it) - are you still good with the latest version ?

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PR: https://git.openjdk.org/jdk/pull/11563