[master] RFR: OMWorld: Decouple deflation and table sizing

[Coleen Phillimore]

On Thu, 23 May 2024 19:18:17 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> The change reverts all changes to deflation and moves the resizing of the OMWorld ConcurrentHashTable to the service thread. Using a similar logic to how we resize the Symbol- and StringTables. 
>> 
>> The option to shrink the table is taken out and can be reintroduced at a later date as an enhancement. To do it correctly the interactions with deflation needs to be figured out.
>
> src/hotspot/share/runtime/serviceThread.cpp line 205:
> 
>> 203:     if (omworldtable_work) {
>> 204:       LightweightSynchronizer::resize_table(jt);
>> 205:     }
> 
> The monitor deflation thread seems like it would be a better place to do the OMWorld table resizing, because it also does cleaning that might be a response to monitor deflation.  The ServiceThread does a lot, and the OMWorld table might notice the stall.  The other thread is also a service thread in a way, so I think this could be moved there instead.

And when we do add shrinking, there'll be interactions with things that the monitor deflation thread is doing.

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PR Review Comment: https://git.openjdk.org/lilliput/pull/175#discussion_r1612194388