libdatadog 28.0.2: integrate libdatadog sample types by r1viollet · Pull Request #504 · DataDog/ddprof

r1viollet · 2026-03-05T17:35:02Z

What does this PR do?

needs following PR: DataDog/libdatadog#1676

  Before (old PROFILE_TYPE_TABLE, passed directly as strings to libdatadog):                                                                                                                                
                                                                
  ┌───────────────┬─────────────────┬───────────────┬─────────────────┬───────────┐                                                                                                                         
  │     Event     │      name       │     unit      │    live name    │ live unit │
  ├───────────────┼─────────────────┼───────────────┼─────────────────┼───────────┤
  │ hardware/misc │ "tracepoint"    │ "events"      │ —               │ —         │
  ├───────────────┼─────────────────┼───────────────┼─────────────────┼───────────┤
  │ sCPU sum      │ "cpu-time"      │ "nanoseconds" │ —               │ —         │
  ├───────────────┼─────────────────┼───────────────┼─────────────────┼───────────┤
  │ sCPU count    │ "cpu-samples"   │ "count"       │ —               │ —         │
  ├───────────────┼─────────────────┼───────────────┼─────────────────┼───────────┤
  │ sALLOC bytes  │ "alloc-space"   │ "bytes"       │ "inuse-space"   │ "bytes"   │
  ├───────────────┼─────────────────┼───────────────┼─────────────────┼───────────┤
  │ sALLOC count  │ "alloc-samples" │ "count"       │ "inuse-objects" │ "count"   │
  └───────────────┴─────────────────┴───────────────┴─────────────────┴───────────┘

  After (now via ddog_prof_SampleType enum → libdatadog Rust mapping):

  ┌────────────────────┬─────────────────┬───────────────┐
  │        Enum        │      name       │     unit      │
  ├────────────────────┼─────────────────┼───────────────┤
  │ SAMPLE (37)        │ "sample"        │ "count"       │
  ├────────────────────┼─────────────────┼───────────────┤
  │ CPU_TIME (4)       │ "cpu-time"      │ "nanoseconds" │
  ├────────────────────┼─────────────────┼───────────────┤
  │ CPU_SAMPLES (5)    │ "cpu-samples"   │ "count"       │
  ├────────────────────┼─────────────────┼───────────────┤
  │ ALLOC_SPACE (3)    │ "alloc-space"   │ "bytes"       │
  ├────────────────────┼─────────────────┼───────────────┤
  │ ALLOC_SAMPLES (0)  │ "alloc-samples" │ "count"       │
  ├────────────────────┼─────────────────┼───────────────┤
  │ INUSE_SPACE (28)   │ "inuse-space"   │ "bytes"       │
  ├────────────────────┼─────────────────┼───────────────┤
  │ INUSE_OBJECTS (27) │ "inuse-objects" │ "count"       │
  └────────────────────┴─────────────────┴───────────────┘

Motivation

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Additional Notes

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How to test the change?

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API changes from v26.0.0: - ddog_prof_Endpoint_agent/agentless gained a use_system_resolver bool. ddprof is an out-of-process profiler that does not fork during export, so use_system_resolver=true (system /etc/resolv.conf) is safe and correct. - ddog_prof_ValueType (name+unit strings) replaced by ddog_prof_SampleType enum; ddog_prof_Period.type_ renamed to .sample_type accordingly. The ValueType->SampleType mapping is expressed as a constexpr lookup table (k_ddog_sample_types) whose rows directly mirror PROFILE_TYPE_TABLE in perf_watcher.hpp. A static_assert on DDPROF_PWT_LENGTH enforces that adding a new profile type requires updating the mapping explicitly. Also add Datadog_LOCAL_ROOT cmake override to Findlibdatadog.cmake to allow testing local libdatadog builds without a GitHub release (skips the fetch script when set).

pr-commenter · 2026-03-05T17:43:25Z

Benchmark results for collatz

Parameters

	Baseline	Candidate
config	baseline	candidate
profiler-version	ddprof 0.23.0+1eae27e1.100340375	ddprof 0.23.0+43269812.100692286

Summary

Found 0 performance improvements and 0 performance regressions! Performance is the same for 1 metrics, 0 unstable metrics.

See unchanged results

scenario	Δ mean execution_time
scenario:ddprof -S bench-collatz --preset cpu_only collatz_runner.sh	same

pr-commenter · 2026-03-05T17:43:28Z

Benchmark results for BadBoggleSolver_run

Parameters

	Baseline	Candidate
config	baseline	candidate
profiler-version	ddprof 0.23.0+1eae27e1.100340375	ddprof 0.23.0+43269812.100692286

Summary

Found 0 performance improvements and 0 performance regressions! Performance is the same for 1 metrics, 0 unstable metrics.

See unchanged results

scenario	Δ mean execution_time
scenario:ddprof -S bench-bad-boggle-solver BadBoggleSolver_run work 1000	unsure [-19.845ms; -10.420ms] or [-0.961%; -0.504%]

r1viollet · 2026-03-05T17:43:49Z

include/perf_watcher.hpp

+
+// Predefined sample type mappings — defined in perf_watcher.cc.
+// Generic sample counting (hardware events, misc software events).
+extern const WatcherSampleTypes k_stype_tracepoint;


slightly strange, adjusting

…mapping Remove the intermediate DDPROF_PWT_* profile type taxonomy and k_ddog_sample_types lookup table, replacing them with WatcherSampleTypes structs that directly store ddog_prof_SampleType integer values per aggregation mode. Key changes: - Remove PROFILE_TYPE_TABLE macro and DDPROF_SAMPLE_TYPES enum - Remove 5 helper functions (sample_type_name_from_idx, etc.) - Add WatcherSampleTypes{sample_types[], count_types[]} to PerfWatcher - Add pprof_active bool to replace the sDUM special-casing - Replace ProfSampleTypes/get_active_ids/compute_pprof_values with a simple SlotRegistry that deduplicates ddog_prof_SampleType slots - Use uint32_t storage to avoid libdatadog header dependency in perf_watcher.cc; static_asserts in ddprof_pprof.cc verify values All 53 tests pass. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

r1viollet · 2026-03-05T18:06:34Z

tracepoints do not work... fixing this

r1viollet · 2026-03-06T12:15:43Z

src/pprof/ddprof_pprof.cc

-    DDPROF_PWT_LENGTH * static_cast<int>(kNbEventAggregationModes);
+// Maps a ddog_prof_SampleType integer value to the kebab-case name used in
+// debug log output (must match what simple_malloc-ut.sh greps for).
+constexpr const char *sample_type_name(uint32_t raw_type) {


we could align with static assert values

- Fix tracepoint count sentinel: k_stype_tracepoint count_types now use k_stype_val_sample (sentinel = no companion) instead of k_stype_val_tracepoint. Previously both pprof_index and pprof_count_index resolved to the same slot, causing the count to overwrite the primary value in pprof_aggregate. - Fix watcher_has_tracepoint to check k_stype_val_tracepoint instead of k_stype_val_sample - Fix debug pprof filename extension from .pprof.lz4 to .pprof.zst (the serialized bytes from libdatadog are zstd-compressed) - Add static_assert for DDOG_PROF_SAMPLE_TYPE_TRACEPOINT == 38 - Use named k_stype_val_* constants in sample_type_name() switch cases - Add static_assert per sample type string to catch future libdatadog renames at compile time Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Replace the outdated DDPROF_PWT_* table with the new WatcherSampleTypes model. Document all three watcher kinds (cpu, alloc, tracepoint), the primary/count companion pattern, the sentinel mechanism, and the compile-time static_assert safety net. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

r1viollet · 2026-03-06T12:26:08Z

src/perf_watcher.cc

      .type = PERF_TYPE_TRACEPOINT,
      .sample_period = 1,
-      .sample_type_id = DDPROF_PWT_TRACEPOINT,
+      .sample_type_info = k_stype_tracepoint,


tracepoints needs the libdatadog change

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

nsavoire · 2026-03-06T15:18:14Z

include/watcher_sample_types.hpp

+
+// CPU: wall/cpu nanoseconds in sum mode, sample count in live mode.
+inline constexpr WatcherSampleTypes k_stype_cpu = {
+    {k_stype_val_cpu_time,    k_stype_val_cpu_samples},


cpu time should not have an associated "live" sample type

nsavoire · 2026-03-06T15:19:18Z

include/watcher_sample_types.hpp

+inline constexpr uint32_t k_stype_val_inuse_objects = 27; // INUSE_OBJECTS
+
+// Generic sample counting (hardware events, misc software events).
+// count_types use the sentinel (k_stype_val_sample) because tracepoints


Using k_stype_val_sample as sentinel feels off

r1viollet commented Mar 5, 2026

View reviewed changes

r1viollet force-pushed the r1viollet/libdatadog_28.0.2 branch from 47c35b8 to 4326981 Compare March 5, 2026 17:48

r1viollet commented Mar 6, 2026

View reviewed changes

r1viollet and others added 2 commits March 6, 2026 13:22

r1viollet commented Mar 6, 2026

View reviewed changes

style: align sample_type_name() cases with static_assert order

475e553

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

nsavoire reviewed Mar 6, 2026

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libdatadog 28.0.2: integrate libdatadog sample types#504

libdatadog 28.0.2: integrate libdatadog sample types#504
r1viollet wants to merge 5 commits intomainfrom
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Benchmark results for collatz

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Benchmark results for BadBoggleSolver_run

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