RFR: 8343205: CompileBroker::possibly_add_compiler_threads excessively polls available memory [v2]

[Martin Doerr]

On Thu, 31 Oct 2024 17:46:17 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Martin Doerr has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Minor improvements (review feedback).
>
> src/hotspot/share/compiler/compileBroker.cpp line 1027:
> 
>> 1025: 
>> 1026:   int old_c2_count = 0, new_c2_count = 0, old_c1_count = 0, new_c1_count = 0;
>> 1027:   const int c2_tasks_per_thread = 2, c1_tasks_per_thread = 4;
> 
> Any reason to have such numbers (2 and 4)?  Any experiments were done to select the best numbers?

Please note that these constants are not new. I have only given them names. I had done some experiments when implementing [JDK-8198756](https://bugs.openjdk.org/browse/JDK-8198756) for JDK11. C1 is faster than C2. Therefore, we can have more C1 tasks per C1 thread.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21812#discussion_r1825304691