RFR: 8330969: scalability issue with loaded JVMTI agent [v3]

[Serguei Spitsyn]

On Tue, 30 Apr 2024 01:56:13 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> This is a fix of the following JVMTI scalability issue. A closed benchmark with millions of virtual threads shows 3X-4X overhead when a JVMTI agent has been loaded. For instance, this is observable when an app is executed under control of the Oracle Studio `collect` utility.
>> For performance analysis, experiments and numbers, please, see the comment below this description.
>> 
>> The fix is to replace the global counter `_VTMS_transition_count` with the mark bit `_VTMS_transition_mark` in each `JavaThread`'.
>> 
>> Testing:
>>  - Tested with mach5 tiers 1-6
>
> Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review: correct comments related to VTMS transition counters

Alex and Chris, thank you for review!

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PR Comment: https://git.openjdk.org/jdk/pull/18937#issuecomment-2088158954