RFR: 8339114: DaCapo xalan performance with -XX:+UseObjectMonitorTable [v3]

[Coleen Phillimore]

On Wed, 26 Mar 2025 07:54:43 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> - When successfully looked up an OM in the OMCache, then make it avaiable in the BasicLock cache. Use that cache whenever possible.
>> - When successfully looked up an OM in the OMCache, then don't push-back the OM on that cache to avoid shuffling the cache on each monitor enter.
>> - In the runtime path of monitorexit, attempt to use the BasicLock cache, then the OMCache, and only look up in the table when the caches failed.
>> - Some small code shufflings.
>> 
>> I did 50 runs of xalan, each of which do 10 warmup iterations before doing one measurement. The following results are the averages of the measurement iterations across the 50 runs:
>> without-OMT: 773.3 ms
>> with-OMT: 797.28 ms
>> 
>> That is still a regression of ~3%
>
> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Include objectMonitor.inline.hpp

So is the issue that the 32 bit x86 code doesn't clear the BasicLock::monitor_cache before going slow path?  I don't see the arm and s390 code doing that either.  So the bug is that the quick-enter code will find a stale monitor?

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PR Comment: https://git.openjdk.org/jdk/pull/24098#issuecomment-2772443092