APM: slab-allocate span attributes in v0.4/v0.5 trace conversion

[ajgajg1134]

What does this PR do?

Reduces memory allocations in the trace-agent receiver when decoding incoming v0.4 and v0.5 trace payloads directly into the internal idx format — i.e. the convert-traces code path.

• Slab-allocate span attributes. In UnmarshalMsgDictionaryConverted (v0.5) and UnmarshalMsgConverted (v0.4), the per-attribute maps (meta, metrics, meta_struct) previously allocated two heap objects per attribute — an AnyValue and its oneof wrapper (AnyValue_StringValueRef / AnyValue_DoubleValue / AnyValue_BytesValue). Each loop now batch-allocates both backing arrays once from the map header count and stores pointers into them.
• Tag _dd.convertedv1 once per v0.5 payload. This debug marker was being set on every span; it is now set only on the first span of the payload.
• Add benchmarks for the converted decode paths: BenchmarkDecodeV04Converted, BenchmarkDecodeV05Converted, and BenchmarkDecodeV05Legacy.

Important

This is an improvement only when convert-traces is enabled (the default). When convert-traces is disabled, the legacy decode path is used and is unaffected by these changes.

Motivation

Profiling the converted v0.5 decode path showed it was allocation-bound: ~1,861 allocs/op, with the AnyValue + oneof-wrapper pair per attribute accounting for ~63% of allocations, and the per-span _dd.convertedv1 tag another ~11%. The same per-attribute pattern exists on the v0.4 path.

Benchmark results

10 chunks × 10 spans, 6 attributes/span (-count=5):

Path	allocs/op	ns/op
v0.5 converted — before	1,861	~41.9µs
v0.5 converted — after	863	~33.1µs
v0.4 converted — before	3,251	~84.4µs
v0.4 converted — after	2,451	~79.3µs

The v0.4 gain is proportionally smaller because that path is dominated by string-table interning (parseStringBytesRef), which this change does not touch.

Behavior change to note

_dd.convertedv1 now appears on only the first span of a converted v0.5 payload rather than on every span. It is a debugging aid, but any downstream tooling that filters/counts spans by this attribute will now see it once per payload. The v0.4 and ConvertToIdx paths are unchanged.

Describe how you validated your changes

• Unit tests pass: pkg/proto/pbgo/trace/idx (81), pkg/proto/pbgo/trace (208), pkg/trace/api (520).
• Before/after benchmarks recorded above via the added BenchmarkDecodeV0{4,5}Converted.

🤖 Generated with Claude Code

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: bf07a6c5a0

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".

[datadog-official]

🎯 Code Coverage (details)
• Patch Coverage: 30.21%
• Overall Coverage: 51.89% (+0.12%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 3d2d40e | Docs | Datadog PR Page | Give us feedback!}

[dd-octo-sts]

Files inventory check summary

File checks results against ancestor 19d25293:

Results for datadog-agent_7.83.0~devel.git.160.3d2d40e.pipeline.125029764-1_amd64.deb:

No change detected

[dd-octo-sts]

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor 19d2529
📊 Static Quality Gates Dashboard
🔗 SQG Job

Successful checks

Info

	Quality gate	Change	Size (prev → curr → max)
✅	agent_deb_amd64_fips	+4.0 KiB (0.00% increase, -0.10% of buffer)	705.880 → 705.884 → 709.840
✅	agent_rpm_amd64_fips	+4.0 KiB (0.00% increase, -0.10% of buffer)	705.864 → 705.868 → 709.840
✅	agent_suse_amd64_fips	+4.0 KiB (0.00% increase, -0.10% of buffer)	705.864 → 705.868 → 709.840
✅	docker_host_profiler_amd64	+2.07 KiB (0.00% increase, -0.01% of buffer)	303.100 → 303.102 → 317.640

28 successful checks with minimal change (< 2 KiB)

	Quality gate	Current Size
✅	agent_deb_amd64	750.991 MiB
✅	agent_heroku_amd64	307.701 MiB
✅	agent_rpm_amd64	750.975 MiB
✅	agent_rpm_arm64	726.058 MiB
✅	agent_rpm_arm64_fips	684.632 MiB
✅	agent_suse_amd64	750.975 MiB
✅	agent_suse_arm64	726.058 MiB
✅	agent_suse_arm64_fips	684.632 MiB
✅	docker_agent_amd64	809.698 MiB
✅	docker_agent_arm64	809.785 MiB
✅	docker_agent_jmx_amd64	1000.595 MiB
✅	docker_agent_jmx_arm64	989.335 MiB
✅	docker_cluster_agent_amd64	209.881 MiB
✅	docker_cluster_agent_arm64	222.952 MiB
✅	docker_cws_instrumentation_amd64	7.447 MiB
✅	docker_cws_instrumentation_arm64	6.877 MiB
✅	docker_dogstatsd_amd64	39.216 MiB
✅	docker_dogstatsd_arm64	37.367 MiB
✅	docker_host_profiler_arm64	314.594 MiB
✅	dogstatsd_deb_amd64	29.955 MiB
✅	dogstatsd_deb_arm64	27.994 MiB
✅	dogstatsd_rpm_amd64	29.955 MiB
✅	dogstatsd_suse_amd64	29.955 MiB
✅	iot_agent_deb_amd64	46.194 MiB
✅	iot_agent_deb_arm64	42.882 MiB
✅	iot_agent_deb_armhf	43.647 MiB
✅	iot_agent_rpm_amd64	46.195 MiB
✅	iot_agent_suse_amd64	46.194 MiB

[cit-pr-commenter-54b7da]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: df1f1b5a-e559-43bc-962f-89e51deb1267

Baseline: 88e6ce0
Comparison: e72c778
Diff

❌ Experiments with retried target crashes

This is a critical error. One or more replicates failed with a non-zero exit code. These replicates may have been retried. See Replicate Execution Details for more information.

• quality_gate_idle_all_features

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	quality_gate_idle_all_features	memory utilization	+0.70	[+0.60, +0.81]	1	Logs bounds checks dashboard
➖	quality_gate_metrics_logs	memory utilization	+0.36	[+0.11, +0.61]	1	Logs bounds checks dashboard
➖	quality_gate_security_no_fs_load	memory utilization	-0.07	[-0.16, +0.02]	1	Logs bounds checks dashboard
➖	quality_gate_idle	memory utilization	-0.20	[-0.26, -0.14]	1	Logs bounds checks dashboard
➖	quality_gate_security_idle	memory utilization	-0.21	[-0.27, -0.16]	1	Logs bounds checks dashboard
➖	quality_gate_security_mean_fs_load	memory utilization	-0.33	[-0.36, -0.29]	1	Logs bounds checks dashboard
➖	quality_gate_logs	% cpu utilization	-0.59	[-1.59, +0.41]	1	Logs bounds checks dashboard

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	observed_value	links
✅	quality_gate_idle	intake_connections	10/10	3 ≤ 4	bounds checks dashboard
✅	quality_gate_idle	memory_usage	10/10	151.43MiB ≤ 154MiB	bounds checks dashboard
✅	quality_gate_idle	total_bytes_received	10/10	729.98KiB ≤ 819.20KiB	bounds checks dashboard
✅	quality_gate_idle_all_features	intake_connections	10/10	3 ≤ 4	bounds checks dashboard
✅	quality_gate_idle_all_features	memory_usage	10/10	492.62MiB ≤ 495MiB	bounds checks dashboard
✅	quality_gate_idle_all_features	total_bytes_received	10/10	1.11MiB ≤ 1.25MiB	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10	4 ≤ 6	bounds checks dashboard
✅	quality_gate_logs	memory_usage	10/10	185.83MiB ≤ 195MiB	bounds checks dashboard
✅	quality_gate_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_logs	total_bytes_received	10/10	264.13MiB ≤ 292MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	cpu_usage	10/10	362.61 ≤ 2000	bounds checks dashboard
✅	quality_gate_metrics_logs	intake_connections	10/10	3 ≤ 6	bounds checks dashboard
✅	quality_gate_metrics_logs	memory_usage	10/10	413.28MiB ≤ 430MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_metrics_logs	total_bytes_received	10/10	0.94GiB ≤ 1.04GiB	bounds checks dashboard
✅	quality_gate_security_idle	cpu_usage	10/10	32.69 ≤ 100	bounds checks dashboard
✅	quality_gate_security_idle	memory_usage	10/10	299.25MiB ≤ 330MiB	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	cpu_usage	10/10	63.86 ≤ 200	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	memory_usage	10/10	277.70MiB ≤ 310MiB	bounds checks dashboard
✅	quality_gate_security_no_fs_load	cpu_usage	10/10	23.30 ≤ 100	bounds checks dashboard
✅	quality_gate_security_no_fs_load	memory_usage	10/10	286.24MiB ≤ 320MiB	bounds checks dashboard

Explanation

Confidence level: 90.00%
Effect size tolerance: |Δ mean %| ≥ 5.00%

Performance changes are noted in the perf column of each table:

• ✅ = significantly better comparison variant performance
• ❌ = significantly worse comparison variant performance
• ➖ = no significant change in performance

A regression test is an A/B test of target performance in a repeatable rig, where "performance" is measured as "comparison variant minus baseline variant" for an optimization goal (e.g., ingress throughput). Due to intrinsic variability in measuring that goal, we can only estimate its mean value for each experiment; we report uncertainty in that value as a 90.00% confidence interval denoted "Δ mean % CI".

For each experiment, we decide whether a change in performance is a "regression" -- a change worth investigating further -- if all of the following criteria are true:

1. Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.

2. Its 90.00% confidence interval "Δ mean % CI" does not contain zero, indicating that if our statistical model is accurate, there is at least a 90.00% chance there is a difference in performance between baseline and comparison variants.

3. Its configuration does not mark it "erratic".

Replicate Execution Details

We run multiple replicates for each experiment/variant. However, we allow replicates to be automatically retried if there are any failures, up to 8 times, at which point the replicate is marked dead and we are unable to run analysis for the entire experiment. We call each of these attempts at running replicates a replicate execution. This section lists all replicate executions that failed due to the target crashing or being oom killed.

Note: In the below tables we bucket failures by experiment, variant, and failure type. For each of these buckets we list out the replicate indexes that failed with an annotation signifying how many times said replicate failed with the given failure mode. In the below example the baseline variant of the experiment named experiment_with_failures had two replicates that failed by oom kills. Replicate 0, which failed 8 executions, and replicate 1 which failed 6 executions, all with the same failure mode.

Experiment	Variant	Replicates	Failure	Logs	Debug Dashboard
experiment_with_failures	baseline	0 (x8) 1 (x6)	Oom killed		Debug Dashboard

The debug dashboard links will take you to a debugging dashboard specifically designed to investigate replicate execution failures.

❌ Retried Normal Replicate Execution Failures (non-profiling)

Experiment	Variant	Replicates	Failure	Debug Dashboard
quality_gate_idle_all_features	baseline	9, 7	Oom killed	Debug Dashboard
quality_gate_idle_all_features	comparison	0	Oom killed	Debug Dashboard

❌ Retried Profiling Replicate Execution Failures (ddprof)

Note: Profiling replicas may still be executing. See the debug dashboard for up to date status.

Experiment	Variant	Replicates	Failure	Debug Dashboard
quality_gate_idle_all_features	baseline	10	Oom killed	Debug Dashboard
quality_gate_metrics_logs	baseline	10	Oom killed	Debug Dashboard
quality_gate_metrics_logs	comparison	10	Oom killed	Debug Dashboard
quality_gate_security_mean_fs_load	baseline	10	Crashed (exit code: 134)	Debug Dashboard
quality_gate_security_no_fs_load	baseline	10	Crashed (exit code: 134)	Debug Dashboard
quality_gate_security_no_fs_load	comparison	10	Crashed (exit code: 134)	Debug Dashboard

CI Pass/Fail Decision

✅ Passed. All Quality Gates passed.

• quality_gate_security_mean_fs_load, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_mean_fs_load, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_no_fs_load, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_no_fs_load, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_idle, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check missed_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check missed_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.

[ajgajg1134]

/merge

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-07-20 14:32:51 UTC ℹ️ Start processing command /merge

---

2026-07-20 14:32:56 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in main is approximately 2h (p90).

---

2026-07-20 15:32:55 UTC ℹ️ MergeQueue: This merge request was merged