RFR: 8350464: The flags to set the native priority for the VMThread and Java threads need a broader range

[David Holmes]

On Fri, 21 Feb 2025 09:01:51 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> See JBS for background details, but basically -1 -> 127 is inappropriate and the priority range should be the full int_min - int_max
>> 
>> Testing:
>>  - tiers 1-3 sanity testing
>> 
>> Thanks
>
> A release note may be useful here. There are a lot of blog articles out there about this topic. I guess this is not a backward compatibility problem, since values lower than -1 have never been accepted by the JVM, right?

Thanks for the reviews @tstuefe and @shipilev .

The -1 quirk is a problem for another day - though hard to imagine it is a practical limitation.

Testing is too hard in general due to the CAP_SYS_NICE problem and the lack of a good way to validate that the change in niceness actually took place.

I'm reluctant to write a Release Note for this simple relaxation of a constraint, as I do not wnat to shine a spotlight (more than already done) on this very murky corner of the runtime. Thread priorities are just a total mess and these flags are very kuch "caveat emptor".

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PR Comment: https://git.openjdk.org/jdk/pull/23722#issuecomment-2677345859