[v4xsh]

Proposed Changes

• The ITT backend now handles the three parcel hooks Tracy got in parcelset,tracing: Emit Tracy events for parcel send and receive #7511 (send, receive, scheduled). Each emits a marker on its own id, with the parcel id (msb, lsb) attached as metadata, plus size, peer locality and source thread where known. An unknown locality is left out.
• No new option: the markers are compiled in with HPX_WITH_PARCEL_PROFILING, like the call sites and Tracy. Its help text now says which backends use it. With the option off (the default), the ITT hooks stay no-ops, so nothing changes for ITT builds by default. The existing HPX_TRACING_MARK_EVENT calls are unchanged.
• New 2-locality test itt_parcel_events, using the recording collector from the tracing tests. It checks that every received parcel has a matching send on the other locality, that large (zero-copy) parcels get a scheduled marker, and that every marker has its id and metadata. The ITT CI job now turns on parcel profiling and runs it.

Any background context you want to provide?

A send and its receive happen in different processes, so each event is a marker on a fresh id, like the work-stealing markers. Send and receive are matched afterwards on the parcel id, like Tracy's text.

The test fails without the backend change (0 markers) and passed every run locally. ITT with parcel profiling off also builds cleanly.

The test checks the ITT calls through the recording collector, not in VTune itself. Not tested: VTune, Windows, the C++20 modules build, and the unknown-locality case.

Checklist

Not all points below apply to all pull requests.

• I have added a new feature and have added tests to go along with it.
• I have fixed a bug and have added a regression test.
• I have added a test using random numbers; I have made sure it uses a seed, and that random numbers generated are valid inputs for the tests.

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• CMakeLists.txt
• libs/core/tracing/include/hpx/tracing/backends/ittnotify.hpp

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📝 Summary

Summary by CodeRabbit

• New Features
  • Added ITTNotify tracing for parcel send, receive, and scheduling events when parcel profiling is enabled.
  • Events include parcel identifiers and relevant locality or thread metadata for distributed-runtime analysis.
• Documentation
  • Clarified parcel profiling support and the event types emitted by supported tracing backends.
• Tests
  • Added integration coverage for ITT parcel events across localities, including small and large parcels.
  • Extended Linux debug validation to run distributed parcel-event tracing tests.

ITTNotify now emits parcel send, receive, and scheduled markers when parcel profiling is enabled. A distributed test validates these markers across two localities. The Linux debug workflow builds and runs the test.

Changes: ITT Parcel Profiling

Layer / File(s)	Summary
ITT parcel marker emission CMakeLists.txt, libs/core/tracing/include/hpx/tracing/backends/ittnotify.hpp, libs/core/tracing/src/backends/ittnotify.cpp	The option description identifies the parcel events emitted by tracing backends. When parcel profiling is enabled, ITTNotify declares and emits parcel send, receive, and scheduled markers with parcel IDs and event metadata. Locality metadata is omitted for the sentinel locality value.
Marker-focused test collection libs/core/tracing/tests/unit/itt_test_collector.cpp	The collector supports marker-only recording and retains metadata and destruction events for tracked marker IDs.
Distributed parcel-event test libs/full/parcelset/tests/unit/itt_parcel_events.cpp	The test loads recorded events, sends small and large parcels between localities, and checks marker creation, destruction, parcel IDs, send sizes, and scheduled source-thread metadata.
Test build and CI wiring libs/core/tracing/tests/unit/CMakeLists.txt, libs/full/parcelset/tests/unit/CMakeLists.txt, .github/workflows/linux_debug_ittnotify.yml	CMake registers the test when ITTNotify and parcel profiling are enabled. The Linux debug workflow enables parcel profiling, builds the test, and adds it to the test filter.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant Test
  participant LocalityA
  participant LocalityB
  participant ITTCollector
  Test->>LocalityA: Send small and large parcels
  LocalityA->>ITTCollector: Record send markers
  LocalityB->>ITTCollector: Record receive and scheduled markers
  Test->>ITTCollector: Read recorded events
  ITTCollector-->>Test: Return marker metadata and parcel IDs

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Merge Risk: ⚪ Minimal · up to aacd6

The change is mergeable with no identified production or test-integration blocker.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 24 functions across 4 files. (1 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title clearly and concisely describes the main change: adding ITT markers for parcel send, receive, and scheduled events.
Description check		The description directly explains the ITT backend changes, parcel profiling behavior, new integration test, and CI coverage.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 24 functions across 4 files. (1 skipped: 1 unsupported.)

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

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Actionable comments posted: 1

---

• 🪄 Fix comments: Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @libs/full/parcelset/tests/unit/itt_parcel_events.cpp:
- Around line 248-252: Configure both zero-copy options in the test registration
for the parcel events test, setting hpx.parcel.zero_copy_optimization and
hpx.parcel.zero_copy_receive_optimization to enabled so large parcels follow the
deferred scheduling path and produce the expected scheduled markers.

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• .github/workflows/linux_debug_ittnotify.yml
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• libs/core/tracing/src/backends/ittnotify.cpp
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[hkaiser]

Thanks, this mirrors the Tracy parcel events well: the markers follow the work-stealing pattern, everything is compiled in only with HPX_WITH_PARCEL_PROFILING, and the test's ordering (scheduled ids before received ids, waiting for late send markers) is sound. A few points:

1. itt_parcel_events takes 92 seconds in the ITT CI job (f8cacab and aacd630), while the other tests there take 0.3 to 3 seconds, and the two earlier runs were killed after 150 to 170 seconds. Do you know where the time goes: the two-locality start-up and shutdown in this Debug + HPX_WITH_VERIFY_LOCKS_BACKTRACE build, or the collector (every ITT call still takes the collector's mutex, and note events are still recorded in markers-only mode)? If it is the collector, filtering more of it would help; either way a TIMEOUT on the test would keep a hang from stalling the job.

2. parcel_ids reads m.metadata.at("parcel_id_msb"), which throws inside the remote action when a marker has no id, so the test fails with an exception before check_markers can report "parcel id missing". Skipping such markers in parcel_ids (or using find) lets check_markers report it.

3. HPX_TEST_LTE(num_bulk * 2, scheduled.size()) compares a number of parcels with a vector of msb/lsb words, which takes a moment to decode; HPX_TEST_LTE(num_bulk, to_set(scheduled).size()) says the same thing directly. The comment above it ("received with zero-copy by default") also predates pinning both zero-copy options in the CMake registration.

4. Nit: invalid_locality (0xFFFFFFFF) is now mirrored in both tracy.cpp and ittnotify.cpp; a shared constant in the tracing module would keep the two from drifting.