Address TestMemHigh flakiness: widen GC slack to 1%

[rdesgroppes]

What does this PR do?

Widen the GC jitter slack in doTestMemHigh from 0.1% (n/1000) to 1% (n/100).

Motivation

The delta assertion (m.Alloc - oldM.Alloc + slack >= n) fails when GC reclaims more than slack bytes between the two ReadMemStats calls.

The CI binary imports many more packages than a local build, producing a ~2.3 MB heap baseline vs ~450 KB locally.
GC reclaims a roughly constant fraction of that baseline, so the absolute reclamation scales with it.
With the earlier 0.1% slack (10'000B for n=10MB), the observed reclamation of 11'256B exceeds the budget and the test fails intermittently (eg#1, eg#2):

INFO: From Testing //pkg/trace/watchdog:watchdog_test:
==================== Test output for //pkg/trace/watchdog:watchdog_test:
--- FAIL: TestMemHigh (2.01s)
    info_test.go:123: Mem (100000 bytes): {2451328} {2558080}
    info_test.go:123: Mem (10000000 bytes): {2451808} {12440552}
    info_test.go:128:
        	Error Trace:	pkg/trace/watchdog/info_test.go:128
        	            				pkg/trace/watchdog/info_test.go:137
        	Error:      	"9998744" is not greater than or equal to "10000000"
        	Test:       	TestMemHigh
        	Messages:   	not enough bytes allocated since last call
FAIL
================================================================================

Widening to 1% (100'000B) clears the largest observed gap by almost an order of magnitude.

Describe how you validated your changes

Standalone harness reproducing CI-like conditions (2MB live baseline, GOGC=1):

go test -tags test -run TestMemHigh ./pkg/trace/watchdog

• old slack n/1000 = 10'000: 1/50 failed (gap 38'008 > 10'000)
• new slack n/100 = 100'000: 0/50 failed (gap 38'008 < 100'000)

[datadog-prod-us1-5]

✨ Fix all issues with BitsAI

⚠️ Warnings

🚦 1 Pipeline job failed

DataDog/datadog-agent | oracle: [21.3.0-xe]     

ℹ️ Info

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 50.73% (+0.01%)

Useful? React with 👍 / 👎

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

[dd-octo-sts]

Files inventory check summary

File checks results against ancestor 2e9ccff8:

Results for datadog-agent_7.81.0~devel.git.638.fcbfaab.pipeline.117801795-1_amd64.deb:

No change detected

[dd-octo-sts]

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor 2e9ccff
📊 Static Quality Gates Dashboard
🔗 SQG Job

32 successful checks with minimal change (< 2 KiB)

	Quality gate	Current Size
✅	agent_deb_amd64	751.652 MiB
✅	agent_deb_amd64_fips	707.423 MiB
✅	agent_heroku_amd64	310.320 MiB
✅	agent_rpm_amd64	751.636 MiB
✅	agent_rpm_amd64_fips	707.407 MiB
✅	agent_rpm_arm64	727.039 MiB
✅	agent_rpm_arm64_fips	686.558 MiB
✅	agent_suse_amd64	751.636 MiB
✅	agent_suse_amd64_fips	707.407 MiB
✅	agent_suse_arm64	727.039 MiB
✅	agent_suse_arm64_fips	686.558 MiB
✅	docker_agent_amd64	811.080 MiB
✅	docker_agent_arm64	811.512 MiB
✅	docker_agent_jmx_amd64	1002.021 MiB
✅	docker_agent_jmx_arm64	991.106 MiB
✅	docker_cluster_agent_amd64	209.753 MiB
✅	docker_cluster_agent_arm64	222.847 MiB
✅	docker_cws_instrumentation_amd64	7.447 MiB
✅	docker_cws_instrumentation_arm64	6.877 MiB
✅	docker_dogstatsd_amd64	39.841 MiB
✅	docker_dogstatsd_arm64	37.946 MiB
✅	docker_host_profiler_amd64	304.525 MiB
✅	docker_host_profiler_arm64	315.638 MiB
✅	dogstatsd_deb_amd64	30.502 MiB
✅	dogstatsd_deb_arm64	28.499 MiB
✅	dogstatsd_rpm_amd64	30.502 MiB
✅	dogstatsd_suse_amd64	30.502 MiB
✅	iot_agent_deb_amd64	45.762 MiB
✅	iot_agent_deb_arm64	42.472 MiB
✅	iot_agent_deb_armhf	43.270 MiB
✅	iot_agent_rpm_amd64	45.762 MiB
✅	iot_agent_suse_amd64	45.761 MiB

[cit-pr-commenter-54b7da]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: a43d9076-7901-4188-97cc-5a615d2e272f

Baseline: 35f1ff3
Comparison: fcbfaab
Diff

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	+0.13	[+0.09, +0.17]	1	Logs bounds checks dashboard
➖	quality_gate_idle	memory utilization	+0.07	[+0.02, +0.13]	1	Logs bounds checks dashboard
➖	quality_gate_metrics_logs	memory utilization	-1.10	[-1.36, -0.83]	1	Logs bounds checks dashboard
➖	quality_gate_logs	% cpu utilization	-1.37	[-2.43, -0.31]	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	145.90MiB ≤ 147MiB	bounds checks dashboard
✅	quality_gate_idle	total_bytes_received	10/10	732.73KiB ≤ 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	494.86MiB ≤ 495MiB	bounds checks dashboard
✅	quality_gate_idle_all_features	total_bytes_received	10/10	1.12MiB ≤ 1.25MiB	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10	3 ≤ 6	bounds checks dashboard
✅	quality_gate_logs	memory_usage	10/10	177.93MiB ≤ 195MiB	bounds checks dashboard
✅	quality_gate_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_logs	total_bytes_received	10/10	264.43MiB ≤ 292MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	cpu_usage	10/10	347.80 ≤ 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	400.85MiB ≤ 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

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 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_idle_all_features	comparison	10	Oom killed	Debug Dashboard
quality_gate_logs	baseline	10	Oom killed	Debug Dashboard
quality_gate_logs	comparison	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

CI Pass/Fail Decision

✅ Passed. All Quality Gates 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_logs, bounds check missed_bytes: 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.
• quality_gate_metrics_logs, bounds check cpu_usage: 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 missed_bytes: 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 total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check memory_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 total_bytes_received: 10/10 replicas passed. Gate passed.