RFR: 8342818: Implement CPU Time Profiling for JFR [v4]

[Markus Grönlund]

On Wed, 30 Oct 2024 21:22:09 GMT, Johannes Bechberger <jbechberger at openjdk.org> wrote:

>> Shouldn't the event have a stackTrace setting and the setting be set to true in default.jfc, similar to ObjectAlllocationSample?
>> 
>> metadata.xml:
>>   <Event name="ObjectAllocationSample" thread="true" stackTrace="true" startTime="false" throttle="true">
>>     <Field type="Class" name="objectClass" label="Object Class" />
>>     <Field type="long" contentType="bytes" name="weight"  />
>>   </Event>
>> 
>> default.jfc:
>>   <event name="jdk.ObjectAllocationSample">
>>     <setting name="enabled">true</setting>
>>     <setting name="throttle">150/s</setting>
>>     <setting name="stackTrace">true</setting>
>>   </event>
>> 
>>  OldObjectSample also works that way, but it has "cutoff" instead of "throttle".
>
> This would also be an option.

> The problem is, is that `eventType.hasStackTrace()` checks for the existence of a field called `stackTrace`, which CPUTimeSample events have. We could of course rename the field to something like `recordedStackTrace`, but I don't think that this is helpful.

Aha - so even if the event is not decorated with stackTrace=true in metadata.xml, it has an explicit field with the same name "StackTrace". Wonder why this should be handled differently from ExecutionSample?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20752#discussion_r1823433881