RFR: 8320318: ObjectMonitor Responsible thread

[Martin Doerr]

On Fri, 20 Sep 2024 08:25:10 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> @TheRealMDoerr 
>>> I've run it through our nightly testing (x86_64, aarch64, PPC64 with several OSes) and the good news is that I haven't seen any functional problems. Performance looks also good for the SPEC benchmarks. I don't think they stress Java monitors very strongly.
>> 
>> That really is good news! Thanks for testing!
>> 
>>> I've rerun the `LockUnlock` micro benchmark with this patch applied, but `LockUnlock.java` reverted to the original version. This makes `LockUnlock.testContendedLock` faster, but not as fast as without this patch (on the 96 Thread Xeon linux server, similar on Power10). Would be great if anybody could confirm. I think this should at least be documented and the description of the JBS issue improved.
>> 
>> Tanks for confirming that my suspension was right. As I stated earlier, due to the added StoreLoad barrier a slight decrease in performance is probably to be expected if you just run `LockUnlock.testContendedLock`, but it shouldn't really matter when running real life applications. Anyhow I'll update the description of the JBS issue.
>
> @fbredber: If you need help to resolve the PPC64 conflicts with https://github.com/openjdk/jdk/commit/7579d3740217e4a819cbf63837ec929f00464585, just let me know.

> @TheRealMDoerr @offamitkumar I resolved merge conflicts in `src/hotspot/cpu/ppc/macroAssembler_ppc.cpp` and `src/hotspot/cpu/s390/macroAssembler_s390.cpp`. I've smoke tested it with QEMU, but it would be nice if you could check if it's ok as well.

Thanks for rebasing! The PPC64 implementation still looks good and some quick tests have passed on real hardware. I'll run more tests.

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PR Comment: https://git.openjdk.org/jdk/pull/19454#issuecomment-2375140146