RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v26]

[Johannes Bechberger]

On Sun, 1 Jun 2025 18:10:15 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

>> Not without allocating in the signal handler
>
> How so?

Because we need to add the threads from the signal handler. So any kind of growing array or set would not work, especially if we want to remove the threads from within the signal handler again.

This is certainly an area of future optimization, albeit this doesn't seem to have any measurable performance impact in my renaissance benchmark runs.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2120492743