RFR: 8317538: Potential bottleneck in Provider::getService: specjvm2008::crypto.rsa have scalability issue for high vCPU numbers [v5]

[Anthony Scarpino]

On Thu, 14 Nov 2024 16:40:22 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.
>
> Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8317538: Potential bottleneck in Provider::getService: specjvm2008::crypto.rsa have scalability issue for high vCPU numbers

ThreadLocal should be `static` as it is storing the per-thread `ServiceKey` variable.
You will want something like this:

private static final ThreadLocal<ServiceKey> previousKey =
        ThreadLocal.withInitial(() -> new ServiceKey("","", false));
```        
Then use previousKey.get() when reading the variable and set() for replacing it.

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PR Comment: https://git.openjdk.org/jdk/pull/21719#issuecomment-2477423556