[USMON-384] Use eBPF ring buffers when supported

[p-lambert]

What does this PR do?

Replace the use of perf maps by ring buffers when supported by the target host (>= 5.8)

Motivation

• Better memory management: ring buffers share a unique buffer across all CPUs which can be beneficial for absorbing burst in the context of uneven workloads. In our load test environment we have seen a marginal (10%) reduction in the number of dropped events (caused by failed perf flushes). Having said that, in relative terms our loss rate was already <0.01%, so I wouldn't expect this to have any impact in terms of overall data correctness.

• Enable future use of reserve/submit API

Additional Notes

• For this PR, we have maintained the total memory allocated for the perf events, but we should now be able to reduce it specially in the context of a high number of CPUs. This will be left as a follow-up PR though.
• We also plan to open another follow-up PR for replacing removeRingBufferHelperCalls by the ebpf.Modifier introduced in https://github.com/DataDog/datadog-agent/pull/23158, but we're currently waiting on another PR that deprecates the use of the eBPF telemetry manager.
• We're now embedding the CPU number "directly" in the event payload because ring buffer events don't have this information. This requires a new field (cpu) to be added to the batch_events_t type, but the size overhead is negligible (<0.01%)

Possible Drawbacks / Trade-offs

Describe how to test/QA your changes

Reviewer's Checklist

• [ ] If known, an appropriate milestone has been selected; otherwise the Triage milestone is set.
• [ ] Use the major_change label if your change either has a major impact on the code base, is impacting multiple teams or is changing important well-established internals of the Agent. This label will be use during QA to make sure each team pay extra attention to the changed behavior. For any customer facing change use a releasenote.
• [ ] A release note has been added or the changelog/no-changelog label has been applied.
• [ ] Changed code has automated tests for its functionality.
• [ ] Adequate QA/testing plan information is provided. Except if the qa/skip-qa label, with required either qa/done or qa/no-code-change labels, are applied.
• [ ] At least one team/.. label has been applied, indicating the team(s) that should QA this change.
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• [ ] If applicable, the need-change/operator and need-change/helm labels have been applied.
• [ ] If applicable, the k8s/<min-version> label, indicating the lowest Kubernetes version compatible with this feature.
• [ ] If applicable, the config template has been updated.

[pr-commenter[bot]]

Bloop Bleep... Dogbot Here

Regression Detector Results

Run ID: f5cf03fc-dfed-498a-bfec-677fd29a5022 Baseline: 6964da53aae4a788c540294470fa574c6539710c Comparison: 3e1e98e9db4e72ca3b9bba6f7b2363e568821a3c

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

Experiments with missing or malformed data

• basic_py_check

Usually, this warning means that there is no usable optimization goal data for that experiment, which could be a result of misconfiguration.

No significant changes in experiment optimization goals

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

There were no significant changes in experiment optimization goals at this confidence level and effect size tolerance.

Experiments ignored for regressions

Regressions in experiments with settings containing erratic: true are ignored.

perf	experiment	goal	Δ mean %	Δ mean % CI
➖	file_to_blackhole	% cpu utilization	+0.30	[-6.23, +6.83]

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI
➖	file_to_blackhole	% cpu utilization	+0.30	[-6.23, +6.83]
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	+0.30	[-1.14, +1.75]
➖	file_tree	memory utilization	+0.28	[+0.18, +0.37]
➖	idle	memory utilization	+0.18	[+0.13, +0.22]
➖	trace_agent_msgpack	ingress throughput	+0.03	[+0.01, +0.05]
➖	uds_dogstatsd_to_api	ingress throughput	+0.00	[-0.00, +0.00]
➖	tcp_dd_logs_filter_exclude	ingress throughput	-0.00	[-0.00, +0.00]
➖	trace_agent_json	ingress throughput	-0.01	[-0.06, +0.04]
➖	process_agent_standard_check	memory utilization	-0.08	[-0.13, -0.03]
➖	process_agent_standard_check_with_stats	memory utilization	-0.23	[-0.27, -0.18]
➖	process_agent_real_time_mode	memory utilization	-0.23	[-0.27, -0.19]
➖	otel_to_otel_logs	ingress throughput	-0.36	[-1.01, +0.29]
➖	tcp_syslog_to_blackhole	ingress throughput	-0.73	[-0.78, -0.67]

Explanation

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".

[p-lambert]

/merge

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