RFR: 8253064: monitor list simplifications and getting rid of TSM [v6]

[Robbin Ehn]

On Tue, 10 Nov 2020 23:24:24 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 robehn and coleenp comments.

src/hotspot/share/runtime/synchronizer.cpp line 1226:

> 1224:         ThreadBlockInVM tbivm(self->as_Java_thread());
> 1225:       }
> 1226:       os::naked_short_sleep(999);  // sleep for almost 1 second

Hi Dan, you need to be blocked while sleeping, otherwise you are blocking safepoints for "almost 1 second".
So previous code was correct.

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