RFR: JDK-8289524: Add JFR JIT restart event

[Markus Grönlund]

On Thu, 30 Jun 2022 13:17:09 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> The JIT compiler restarts (see restart_compiler in NMethodSweeper::sweep_code_cache) would be a helpful addition to the JFR events. Currently we log the JIT stop operations in JFR (EventCodeCacheFull) but no restart.

Thanks for considering. It is fine to move the EventSweepCodeCache event around, you can see that the constructor takes the UNTIMED value. This means that timestamping is handled explicitly, by setting the set_starttime() and set_endtime() fields For compatibility, we can think of it like we are creating a subclass with extended fields. Just append the additional fields to the event. As for the memory field declarations, you can take a peek at other events in metadata.xml, for example, this field declaration is from CodeCacheFull:

    <Field type="ulong" contentType="bytes" name="unallocatedCapacity" label="Unallocated" />

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PR: https://git.openjdk.org/jdk/pull/9334