RFR: 8357481: Excessive CompileTask wait/notify monitor creation

[Aleksey Shipilev]

On Wed, 21 May 2025 18:40:24 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> See bug for rationale.
> 
> This PR implements the 2nd solution from the bug: lift the lock to be global. As described in the bug, excess locking work would realistically affect Xcomp, and only in a minor way. But we will reap a minor footprint/latency benefit by not constructing the lock for every `CompileTask`.
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `compiler`
>  - [x] Linux x86_64 server fastdebug, `all`
>  - [x] Linux AArch64 server fastdebug, `all`

Testing is all green here. Waiting for reviews :)

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PR Comment: https://git.openjdk.org/jdk/pull/25364#issuecomment-2901688418