[jdk8u-dev] RFR: 8304074: [JMX] Add an approximation of total bytes allocated on the Java heap by the JVM [v3]

[Paul Hohensee]

On Mon, 26 Feb 2024 19:27:00 GMT, Paul Hohensee <phh at openjdk.org> wrote:

>> I'd like to backport the definition and implementation of com.sun.management.ThreadMXBean.getTotalThreadAllocatedBytes to 8u. The backport CSR is [JDK-8320375](https://bugs.openjdk.org/browse/JDK-8320375). A follow-up bugfix backport of [JDK-8313081](https://bugs.openjdk.org/browse/JDK-8313081) will be done following this backport. The combined backports have been in production at Amazon for two months with no issues. The backport uses the reserved1 slot in jmm.h in order to preserve binary compatibility with 8u. Per current policy, there is no update to JMM_VERSION in jmm.h and the new method is marked
>> 
>> @since 8u412
>> 
>> Aside from file relocation and context differences, relative to the 11u backport the MonitoringSupport_lock definition macro changes, and the reserved1 rather than reserved6 jmm slot is used. SMR doesn't exist in 8u, so jmm_GetTotalThreadAllocated bytes attempts to lock Threads_lock instead, and if the Threads_lock is already locked, the previous return value is returned. HotSpotThreadImpl.java doesn't exist in 8u, so the hunk associated with it is dropped.
>
> Paul Hohensee has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:
> 
>  - Merge branch 'master' into backport-8304074
>  - 8304074: whitespace fix
>  - 8304074: make @since 8u412
>  - Merge branch 'master' into backport-8304074
>  - Merge branch 'master' into backport-8304074
>  - Backport 3eced01f9efe2567a07b63343f8559683a2d0517

GHA failure is unrelated: passes on my development box.

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PR Comment: https://git.openjdk.org/jdk8u-dev/pull/392#issuecomment-1965482081