8387552: [lworld] Add new capability to enable value objects support for JVMTI VMObjectAlloc and SampledObjectAlloc

[sspitsyn]

This update is for Valhalla pre-integration. It introduces new JVMTI capability can_support_value_objects.
The variable _can_support_value_objects_count is introduced for optimization. It follows the pattern of the can_support_virtual_threads capability.

Additionally, this update includes test fixes:

• test/hotspot/jtreg/serviceability/jvmti/HeapMonitor/libHeapMonitorTest.cpp:

  • Removed the if (!jni->HasIdentity(object)) check because it is not needed anymore as the JVMTI capability can_support_value_objects is no acquired by the test

• These two tests are updated to provide both positive and negative coverage for new capability:
  test/hotspot/jtreg/serviceability/jvmti/valhalla/VMObjectAllocValue
  test/hotspot/jtreg/serviceability/jvmti/valhalla/SampledObjectAllocValue

Testing:

• Ran updated tests locally
• Submitted mach5 tiers 1-6

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Progress

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Issue

• JDK-8387552: [lworld] Add new capability to enable value objects support for JVMTI VMObjectAlloc and SampledObjectAlloc (Enhancement - P4)

Reviewers

• Leonid Mesnik (@lmesnik - Committer) ⚠️ Review applies to ee6e61d7
• Chris Plummer (@plummercj - Committer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/valhalla.git pull/2607/head:pull/2607
$ git checkout pull/2607

Update a local copy of the PR:
$ git checkout pull/2607
$ git pull https://git.openjdk.org/valhalla.git pull/2607/head

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Checkout this PR locally:
$ git pr checkout 2607

View PR using the GUI difftool:
$ git pr show -t 2607

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Download this PR as a diff file:
https://git.openjdk.org/valhalla/pull/2607.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

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[openjdk]

@sspitsyn This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8387552: [lworld] Add new capability to enable value objects support for JVMTI VMObjectAlloc and SampledObjectAlloc

Reviewed-by: lmesnik, cjplummer

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 16 new commits pushed to the lworld branch:

• 650d7b4: 8387484: [lworld] javac should warn on use of value classes
• 166b653: 8387374: [lworld] Address test issues in test/jdk/java/io/Serializable/valueObjects/ValueSerializationTest.java
• 046c69b: 8387624: [lworld] cherry-pick JDK-8387265 G1: Shutdown during concurrent cycle leaves SATB queues in inconsistent state
• ... and 13 more: https://git.openjdk.org/valhalla/compare/3a3ac5cf3e6872952a88906b597948215eb769d3...lworld

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the lworld branch, type /integrate in a new comment.

[mlbridge]

Webrevs

• 02: Full - Incremental (f6b54a55)
• 01: Full - Incremental (3c8ef304)
• 00: Full (ee6e61d7)

[lmesnik]

I reviewed the implementation and tests only, assuming that CSR will be approved.

The only general comment is that implementation doesn't check the '--enable-preview' so agent with enabled 'can_support_value_objects' is not going to fail.

Do we need a separate test for this?

Also, there is a general lack of coverage of this behaviour for multi environments/agents.

Might be needed to to file RFE to review './vmTestbase/nsk/jvmti/scenarios/multienv' and see if they should be updated or write new tests.

There are few comments inline.

[sspitsyn]

The only general comment is that implementation doesn't check the '--enable-preview' so agent with enabled 'can_support_value_objects' is not going to fail. Do we need a separate test for this?

Thank you for looking at this change! This does not look as a real problem.
The runtime event paths already make the relevant behavioral decision from the actually allocated object:
const bool is_inline = object->is_inline();

Also, there is a general lack of coverage of this behaviour for multi environments/agents.
Might be needed to to file RFE to review './vmTestbase/nsk/jvmti/scenarios/multienv' and see if they should be updated or write new tests.

Yes. We have a lack of coverage in this area. I hope, it is not a stopper for this PR. :)

[plummercj]

It's a little unclear to me how this all works when not in preview mode. Does the jvmti client still get to enable can_support_value_objects, but it has no affect.

[AlanBateman]

It's a little unclear to me how this all works when not in preview mode. Does the jvmti client still get to enable can_support_value_objects, but it has no affect.

I think this came up with can_support_virtual_threads capability when virtual threads were in preview. I think we concluded that it's benign as it needs both the capability and preview features be enabled.

[sspitsyn]

Chris and Leonid, thank you for review!

[sspitsyn]

/integrate

[openjdk]

Going to push as commit 3a7e2e0.
Since your change was applied there have been 16 commits pushed to the lworld branch:

• 650d7b4: 8387484: [lworld] javac should warn on use of value classes
• 166b653: 8387374: [lworld] Address test issues in test/jdk/java/io/Serializable/valueObjects/ValueSerializationTest.java
• 046c69b: 8387624: [lworld] cherry-pick JDK-8387265 G1: Shutdown during concurrent cycle leaves SATB queues in inconsistent state
• ... and 13 more: https://git.openjdk.org/valhalla/compare/3a3ac5cf3e6872952a88906b597948215eb769d3...lworld

Your commit was automatically rebased without conflicts.

[openjdk]

@sspitsyn Pushed as commit 3a7e2e0.

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