RFR: 8253064: monitor list simplifications and getting rid of TSM [v3]

[David Holmes]

On Mon, 9 Nov 2020 20:51:17 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

>> Changes from @fisk and @dcubed-ojdk to:
>> 
>> - simplify ObjectMonitor list management
>> - get rid of Type-Stable Memory (TSM)
>> 
>> This change has been tested with Mach5 Tier[1-3],4,5,6,7,8; no new regressions.
>> Aurora Perf runs have also been done (DaCapo-h2, Quick Startup/Footprint,
>> SPECjbb2015-Tuned-G1, SPECjbb2015-Tuned-ParGC, Volano)
>>   - a few minor regressions (<= -0.24%)
>>   - Volano is 6.8% better
>> 
>> Eric C. has also done promotion perf runs on these bits and says "the results look fine".
>
> Daniel D. Daugherty has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Resolve more @dholmes-ora comments with help from @fisk.

src/hotspot/share/runtime/synchronizer.cpp line 89:

> 87:   ObjectMonitor* head = Atomic::load_acquire(&_head);
> 88:   ObjectMonitor* m = head;
> 89:   do {

This wasn't the loop I was referring to. It is the while loop below this at line 93.

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PR: https://git.openjdk.java.net/jdk/pull/642