RFR: JDK-8289524: Add JFR JIT restart event [v4]

[Matthias Baesken]

On Fri, 15 Jul 2022 12:13:48 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.
>
> Matthias Baesken has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Adjust test, contentType and label info

Hi , I adjusted the contentType as suggested, adjusted the label  and TestCodeCacheFull.
Regarding triggering the JitRestart event , the  suggested TestCodeCacheFull looks like a good start . So I  added to allocateCodeBlob (this triggers the CodeCacheFull event)  a  corresponding freeCodeBlob call .
Unfortunately this did not work in practise and doesn't show the JitRestart event.  There could be some delay to the restarting unfortunately.

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