RFR: 8318986: Improve GenericWaitBarrier performance [v5]

[Aleksey Shipilev]

On Tue, 14 Nov 2023 11:03:43 GMT, Claes Redestad <redestad at openjdk.org> wrote:

> > Most quick benchmarks are done, but the bulk will take the night to complete.
> 
> All done, nothing else that stands out across a medium-size set (400+) of benchmark runs. One caveat is that we don't configure all that many server-style and intentionally large GC-heavy benchmarks on Windows and MacOS hosts, so we might have a bit of a blind spot here that I'll see if we can improve.

Thank you! 

I tend to suggest that we do not treat current performance data as the blocker for integration. The realistic cases -- when systems are have more runnable threads than CPUs -- do benefit from this optimization substantially. I wouldn't expect well-tuned benchmarking environments suffer from this problem.

FWIW, I ran `RSABench` on Mac and I cannot see the regression, so at least on Mac we look safe. I have no quiet Windows machine readily available to verify it there. I merged from master and removed the Linux switch, in case you want to run this again.


Benchmark         Mode  Cnt      Score    Error  Units

# Baseline
RSABench.decrypt  thrpt   40   1043,037 ?  1,137  ops/s
RSABench.encrypt  thrpt   40  35054,674 ? 19,084  ops/s

# Patched
RSABench.decrypt  thrpt   40   1042,407 ?  1,838  ops/s
RSABench.encrypt  thrpt   40  35056,418 ? 46,026  ops/s

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PR Comment: https://git.openjdk.org/jdk/pull/16404#issuecomment-1810337115