RFR: 8276660: Scalability bottleneck in java.security.Provider.getService() [v2]

[Weijun Wang]

On Wed, 24 Nov 2021 21:17:34 GMT, Valerie Peng <valeriep at openjdk.org> wrote:

>> It is observed that when running crypto benchmark with large number of threads, a lot of time is spent on the synchronized block inside the Provider.getService() method. The cause for this is that Provider.getService() method first uses the 'serviceMap' field to find the requested service. However, when the requested service is not supported by this provider, e.g. requesting Cipher.RSA from SUN provider, the impl continues to try searching the legacy registrations whose processing is guarded by the "synchronized" keyword. When apps use getInstance() calls without the provider argument, Provider class has to iterate through existing providers trying to find one that supports the requested service.
>> 
>> Now that the parent class of Provider no longer synchronizes all of its methods, Provider class should follow suit and de-synchronize its methods. Parsing of the legacy registration is done eagerly (at the time of put(...) calls) instead of lazily (at the time of getService(...) calls). This also makes "legacyStrings" redundant as the registration is parsed and stored directly into "legacyMap". 
>> 
>> The bug reporter has confirmed that the changes resolve the performance bottleneck and all regression tests pass.
>> 
>> Please review and thanks in advance,
>> Valerie
>
> Valerie Peng has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Updated to use pattern matching with instanceof operator.

Consider this case, two threads are changing a value at the same time. Since the method is not synchonized, thread1 might finish the first part of the method (`super.replace`) earlier than thread2, but it finishes the second part (`parseLegacy`) later than thread2. At the end, the internal entrySet has thread2's value but the legacy map has thread1's value.

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PR: https://git.openjdk.java.net/jdk/pull/6513