RFR: 8317538: RSA have scalability issue for high vCPU numbers

[Claes Redestad]

On Mon, 21 Oct 2024 18:18:12 GMT, Vladimir Ivanov <vaivanov at openjdk.org> wrote:

> This patch remove access to the shared variable to fix scalability issue in the multithread environment.  According to testing by the specjvm2008::crypto.rsa the one thread performance reduced for less than 1% while the score for the multithread run increased in ~2x. For the 2 socket system with Xeon 8480+ numbers looks as: 
> - 1 thread: 643.15 for original version vs 642.54 for patched one;
> - 224 threads: 22446.19 for original vs 46147.41 for patched.
> 
> The RSABench microbenchmark reports no score changes for the 1 thread (average for all testcases) and 2.4% improvement for the 224 threads.

The bug description needs to be updated to reflect that this is a potential bottleneck in `Provider::getService` and not isolated to RSA. 

Other than that I think this is a reasonable patch. Removing a bottleneck from specjvm2008.rsa will - if not else - ensure such benchmarks focus better on the stuff that matters.

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Changes requested by redestad (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/21622#pullrequestreview-2385305097