RFR: 8191786: Thread-SMR hash table size should be dynamic [v2]

[Daniel D.Daugherty]

On Tue, 25 May 2021 20:39:56 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

>> Small change to switch Thread-SMR's hash table from ResourceHashtable to KVHashtable
>> so that a variable sized hash table is used instead of a fixed size hash table (1031 elements).
>> Also refactor common hash table size calculation code into static hash_table_size()
>> function and call it from both places.
>> 
>> Test with Mach5 Tier[1-7] testing.
>
> Daniel D. Daugherty has updated the pull request incrementally with one additional commit since the last revision:
> 
>   rehn CR

@fisk - Thanks for chiming in on this thread.

@coleenp - I tried adding free_entries() support, but I wasn't able to get the code to build. Thanks for filing https://bugs.openjdk.java.net/browse/JDK-8267752 so someone can followup on KVHashtable entry freeing.

@dholmes-ora - Agreed that I have no idea what the performance impact would be and I don't want to take the time to figure that out so I'm going to rewind and go the other route that has been discussed for this bug:

- remove the unused hash_code_size calculations
- leave the Thread-SMR hash table at 1031 elements since it has been that way since JDK10-B36 (integrated on 2017.11.24)

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PR: https://git.openjdk.java.net/jdk/pull/4168