RFR: 8369449: Spec: introduce new JVMTI function GetTotalGCCpuTime [v3]

[Jonas Norlinder]

On Sat, 18 Oct 2025 00:56:25 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> With [JDK-8359110](https://bugs.openjdk.org/browse/JDK-8359110) a framework to measure GC CPU time was introduced.
>> It will be exposed in JMX as `MemoryMXBean.getTotalGcCpuTime()`. There is also interest to get the same performance data from JVMTI.
>> The following API's are being added with this enhancement:
>> 
>> Introduce:
>>  - new capability: `can_get_gc_cpu_time`
>>  - new JVMTI functions:
>>     - `jvmtiError GetGCCpuTimerInfo(jvmtiEnv* env, jvmtiTimerInfo* info_ptr)`
>>     - `jvmtiError GetTotalGCCpuTime(jvmtiEnv* env, jlong* nanos_ptr)`
>> 
>> **CSR**: [8370159](https://bugs.openjdk.org/browse/JDK-8370159): Spec: introduce new JVMTI function GetTotalGCCpuTime
>> 
>> Testing:
>>  - TBD: Mach5 tiers 1-6
>
> Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fix a typo in GetGCCpuTimerInfo: long => jlong

src/hotspot/share/prims/jvmtiH.xsl line 120:

> 118:     JVMTI_VERSION_19  = 0x30130000,
> 119:     JVMTI_VERSION_21  = 0x30150000,
> 120:     JVMTI_VERSION_25  = 0x30170000,

Should this be `JVMTI_VERSION_26` if this is targeted for version 26?

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PR Review Comment: https://git.openjdk.org/jdk/pull/27879#discussion_r2443390372