RFR: 8348402: PerfDataManager stalls shutdown for 1ms [v4]

[David Holmes]

On Fri, 31 Jan 2025 08:30:29 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Found this when studying Leyden performance. [JDK-8049304](https://bugs.openjdk.org/browse/JDK-8049304) added 1ms sleep on destruction path to catch up with threads updating the counters. 
>> 
>> I was not able to confidently prove the deletion race is benign. Even though `sleep` is not really a fix for that race either, I think it is safer to use GlobalCounter to coordinate deletions.
>> 
>> This improves startup (roundtrip) tests for the expected 1ms:
>> 
>> 
>> $ hyperfine -w 10 -r 100 ...
>> 
>> # Before
>> Benchmark 1: build/linux-x86_64-server-release/images/jdk/bin/java -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -Xmx128m Hello
>>   Time (mean ± σ):      20.0 ms ±   0.3 ms    [User: 11.7 ms, System: 16.0 ms]
>>   Range (min … max):    19.0 ms …  21.7 ms    1000 runs
>> 
>> # After
>> Benchmark 1: build/linux-x86_64-server-release/images/jdk/bin/java -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -Xmx128m Hello
>>   Time (mean ± σ):      19.0 ms ±   0.3 ms    [User: 11.9 ms, System: 15.8 ms]
>>   Range (min … max):    18.2 ms …  20.8 ms    1000 runs
>> 
>> 
>> Additional testing:
>>  - [x] Linux AArch64 server fastdebug, `all`
>>  - [x] Linux x86_64 server fastdebug, `all`
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   David's review: more comments. Also reinstate has_PerfData in unprotected update.

That all seems fine enough to me. Thanks.

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/23293#pullrequestreview-2586271530