RFR: 8266642: improve ResolvedMethodTable hash function [v2]

[Denghui Dong]

On Tue, 11 May 2021 02:35:13 GMT, Denghui Dong <ddong at openjdk.org> wrote:

>> But as you note, the name mangling for hidden classes would mean that the names are not actually the same. And I don't see how this introduces a different classloader-data. ??
>
> Unsafe.getUnsafe().defineAnonymousClass will create an unsafe anonymous class rather than a hidden class, and for unsafe anonymous class, JVM will create a new CLD, see the comment in SystemDictionary::resolve_hidden_class_from_stream:
> 
>   // - for unsafe anonymous class: create a new CLD whith a class holder that uses
>   //                               the same class loader as the unsafe_anonymous_host.
>   // - for hidden classes that are not strong: create a new CLD that has a class holder and
>   //                                           whose loader is the Lookup class's loader.
>   // - for hidden class: add the class to the Lookup class's loader's CLD.

> Okay but we should only be concerned about the behaviour of public 
> API's, so we should be testing and benchmarking those API's.

> defineAnonymousClass() maybe relevant for 11u, but not mainline.

I can use public API.
Another reason I used Unsafe API here is for saving metaspace.

-------------

PR: https://git.openjdk.java.net/jdk/pull/3901