RFR: 8356968: JFR: Compilation event should be enabled for all compilations by default

[Aleksey Shipilev]

On Thu, 15 May 2025 08:49:47 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> In the field, we are using -XX:+PrintCompilation to track compiler performance. Alternatively, -Xlog:jit* prints the same. JFR has a the related jdk.Compilation event that gives us even richer diagnostics. Yet, that event is set at a very high threshold (1000ms), which skips almost all compilations! This threshold is set to such a high value from the beginning. 
> 
> It is fairly normal to have lots of compilations in 100+ ms range individually, and their sum impact is what we are after. Also, the compilations are normally quite rare, and there are a couple of thousands of compiles in most workloads, and they only happen sporadically. This means, the event count without any threshold is not high.
> 
> Therefore, it would be convenient to make sure that basic Compilation event is enabled unconditionally, e.g. by dropping the default threshold to 0.
> 
> See more logs in the bug itself.
> 
> Additional testing:
>  - [x] Ad-hoc tests with printing compilation events
>  - [x] Linux x86_64 server fastdebug, `jdk_jfr`

I think @iwanowww had an opinion on this :)

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PR Comment: https://git.openjdk.org/jdk/pull/25247#issuecomment-2934586864