[CONTP-1135] Support docker.cpu.shares metric on cgroups v2 with runc >= 1.3.2

[zhuminyi]

What does this PR do?

• Auto-detect which conversion formula the runtime uses by comparing the actual cgroup weight with expected values from Docker Inspect
• Support both old (linear) and new (quadratic) formulas for backward compatibility
• Use the geometric mean approach for the inverse formula to handle ceil() rounding

New formula for shares to weight:

  exponent = (l² + 125l) / 612 - 7/34; 
  weight = ceil(10^exponent)

We are doing inverse formula to get shares from weight in this PR:
See cpuWeightToSharesNonLinear(cpuWeight float64) function, same logic can be found in other reference: https://github.com/cloudfoundry/guardian/blob/main/rundmc/utils.go

Motivation

On cgroups v2 systems running runc >= 1.3.2 (or crun >= 1.23), the docker.cpu.shares metric reported incorrect values. For example, containers configured with the default --cpu-shares 1024 would show
2597 instead of 1024.

Root cause: The container runtime changed its CPU shares-to-weight conversion formula from linear to quadratic (opencontainers/runc#4785), but the Agent was still using the old linear inverse formula.

Old formula (linear):

• weight = 1 + ((shares - 2) * 9999) / 262142
• 1024 shares → weight 39 (incorrect default mapping)

New formula (quadratic):

• Uses logarithmic function to ensure min, max, and default values align
• 1024 shares → weight 100 (correct default mapping)

The Datadog Agent was using the old formula's inverse to convert weight back to shares, causing:

• With new runc: weight 100 → 2597 shares (should be 1024)

Describe how you validated your changes

unit test

Additional Notes

[agent-platform-auto-pr]

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor 9f6f936

Successful checks

Info

	Quality gate	Delta	On disk size (MiB)	Delta	On wire size (MiB)
✅	agent_deb_amd64	$${+0.01}$$	$${705.45}$$ < $${706.32}$$	$${+0.02}$$	$${172.88}$$ < $${173.81}$$
✅	agent_deb_amd64_fips	$${+0}$$	$${700.79}$$ < $${701.16}$$	$${-0}$$	$${171.83}$$ < $${172.71}$$
✅	agent_heroku_amd64	$${+0}$$	$${327.25}$$ < $${327.69}$$	$${-0.01}$$	$${87.24}$$ < $${88.19}$$
✅	agent_msi	$${+0.02}$$	$${568.82}$$ < $${982.08}$$	$${+0.03}$$	$${141.75}$$ < $${143.01}$$
✅	agent_rpm_amd64	$${+0.01}$$	$${705.44}$$ < $${706.31}$$	$${+0.02}$$	$${175.92}$$ < $${176.86}$$
✅	agent_rpm_amd64_fips	$${+0}$$	$${700.78}$$ < $${701.15}$$	$${+0.03}$$	$${173.98}$$ < $${174.95}$$
✅	agent_rpm_arm64	$${+0.01}$$	$${691.11}$$ < $${691.67}$$	$${-0.01}$$	$${159.68}$$ < $${160.7}$$
✅	agent_rpm_arm64_fips	$${+0}$$	$${687.33}$$ < $${687.54}$$	$${-0.01}$$	$${159.17}$$ < $${160.1}$$
✅	agent_suse_amd64	$${+0.01}$$	$${705.44}$$ < $${706.31}$$	$${+0.02}$$	$${175.92}$$ < $${176.86}$$
✅	agent_suse_amd64_fips	$${+0}$$	$${700.78}$$ < $${701.15}$$	$${+0.03}$$	$${173.98}$$ < $${174.95}$$
✅	agent_suse_arm64	$${+0.01}$$	$${691.11}$$ < $${691.67}$$	$${-0.01}$$	$${159.68}$$ < $${160.7}$$
✅	agent_suse_arm64_fips	$${+0}$$	$${687.33}$$ < $${687.54}$$	$${-0.01}$$	$${159.17}$$ < $${160.1}$$
✅	docker_agent_amd64	$${+0.01}$$	$${767.78}$$ < $${768.66}$$	$${+0.01}$$	$${260.62}$$ < $${261.52}$$
✅	docker_agent_arm64	$${+0.01}$$	$${777.72}$$ < $${778.35}$$	$${+0}$$	$${250.78}$$ < $${251.72}$$
✅	docker_agent_jmx_amd64	$${+0.01}$$	$${958.66}$$ < $${959.54}$$	$${+0}$$	$${329.26}$$ < $${330.15}$$
✅	docker_agent_jmx_arm64	$${+0.01}$$	$${957.32}$$ < $${957.95}$$	$${+0}$$	$${315.4}$$ < $${316.35}$$
✅	docker_cluster_agent_amd64	$${0}$$	$${179.09}$$ < $${179.28}$$	$${+0}$$	$${63.24}$$ < $${63.96}$$
✅	docker_cluster_agent_arm64	$${+0}$$	$${196.58}$$ < $${196.79}$$	$${-0}$$	$${59.96}$$ < $${60.69}$$
✅	docker_cws_instrumentation_amd64	$${0}$$	$${7.07}$$ < $${7.12}$$	$${0}$$	$${2.95}$$ < $${3.29}$$
✅	docker_cws_instrumentation_arm64	$${0}$$	$${6.69}$$ < $${6.92}$$	$${+0}$$	$${2.71}$$ < $${3.07}$$
✅	docker_dogstatsd_amd64	$${0}$$	$${38.65}$$ < $${39.3}$$	$${+0}$$	$${14.93}$$ < $${15.76}$$
✅	docker_dogstatsd_arm64	$${0}$$	$${37.3}$$ < $${37.94}$$	$${-0}$$	$${14.37}$$ < $${14.83}$$
✅	dogstatsd_deb_amd64	$${0}$$	$${29.87}$$ < $${30.53}$$	$${-0}$$	$${7.87}$$ < $${8.75}$$
✅	dogstatsd_deb_arm64	$${0}$$	$${28.38}$$ < $${29.11}$$	$${-0}$$	$${6.81}$$ < $${7.71}$$
✅	dogstatsd_rpm_amd64	$${0}$$	$${29.87}$$ < $${30.53}$$	$${-0}$$	$${7.89}$$ < $${8.76}$$
✅	dogstatsd_suse_amd64	$${0}$$	$${29.87}$$ < $${30.53}$$	$${-0}$$	$${7.89}$$ < $${8.76}$$
✅	iot_agent_deb_amd64	$${0}$$	$${42.6}$$ < $${43.19}$$	$${-0}$$	$${11.13}$$ < $${11.98}$$
✅	iot_agent_deb_arm64	$${0}$$	$${40.34}$$ < $${40.92}$$	$${+0}$$	$${9.58}$$ < $${10.45}$$
✅	iot_agent_deb_armhf	$${0}$$	$${40.24}$$ < $${40.86}$$	$${-0}$$	$${9.69}$$ < $${10.56}$$
✅	iot_agent_rpm_amd64	$${0}$$	$${42.6}$$ < $${43.19}$$	$${-0}$$	$${11.14}$$ < $${12.0}$$
✅	iot_agent_suse_amd64	$${0}$$	$${42.6}$$ < $${43.19}$$	$${-0}$$	$${11.14}$$ < $${12.0}$$

[cit-pr-commenter]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 4fccadc5-eff1-4898-b141-848d5b58741f

Baseline: 9f6f936
Comparison: 2165b8e
Diff

Optimization Goals: ✅ No significant changes detected

Experiments ignored for regressions

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

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
❌	docker_containers_cpu	% cpu utilization	+5.39	[+2.22, +8.55]	1	Logs

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
❌	docker_containers_cpu	% cpu utilization	+5.39	[+2.22, +8.55]	1	Logs
➖	quality_gate_logs	% cpu utilization	+0.27	[-1.20, +1.73]	1	Logs bounds checks dashboard
➖	quality_gate_idle_all_features	memory utilization	+0.22	[+0.18, +0.25]	1	Logs bounds checks dashboard
➖	otlp_ingest_metrics	memory utilization	+0.20	[+0.05, +0.35]	1	Logs
➖	ddot_metrics_sum_cumulative	memory utilization	+0.13	[-0.03, +0.29]	1	Logs
➖	docker_containers_memory	memory utilization	+0.05	[-0.02, +0.12]	1	Logs
➖	ddot_metrics	memory utilization	+0.05	[-0.17, +0.27]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	+0.03	[-0.38, +0.45]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	+0.03	[-0.34, +0.41]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.01	[-0.08, +0.09]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	-0.00	[-0.13, +0.12]	1	Logs
➖	uds_dogstatsd_to_api_v3	ingress throughput	-0.01	[-0.14, +0.12]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	-0.03	[-0.44, +0.38]	1	Logs
➖	otlp_ingest_logs	memory utilization	-0.04	[-0.14, +0.06]	1	Logs
➖	ddot_metrics_sum_cumulativetodelta_exporter	memory utilization	-0.04	[-0.27, +0.18]	1	Logs
➖	uds_dogstatsd_20mb_12k_contexts_20_senders	memory utilization	-0.05	[-0.10, +0.01]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	-0.06	[-0.11, -0.01]	1	Logs
➖	ddot_logs	memory utilization	-0.17	[-0.24, -0.10]	1	Logs
➖	ddot_metrics_sum_delta	memory utilization	-0.38	[-0.60, -0.16]	1	Logs
➖	quality_gate_idle	memory utilization	-0.41	[-0.45, -0.36]	1	Logs bounds checks dashboard
➖	quality_gate_metrics_logs	memory utilization	-0.45	[-0.67, -0.23]	1	Logs bounds checks dashboard
➖	file_tree	memory utilization	-0.82	[-0.91, -0.74]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	-2.30	[-2.39, -2.21]	1	Logs

Bounds Checks: ❌ Failed

perf	experiment	bounds_check_name	replicates_passed	links
✅	docker_containers_cpu	simple_check_run	10/10
✅	docker_containers_memory	memory_usage	10/10
✅	docker_containers_memory	simple_check_run	10/10
✅	file_to_blackhole_0ms_latency	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency	memory_usage	10/10
✅	file_to_blackhole_1000ms_latency	lost_bytes	10/10
✅	file_to_blackhole_1000ms_latency	memory_usage	10/10
✅	file_to_blackhole_100ms_latency	lost_bytes	10/10
✅	file_to_blackhole_100ms_latency	memory_usage	10/10
✅	file_to_blackhole_500ms_latency	lost_bytes	10/10
✅	file_to_blackhole_500ms_latency	memory_usage	10/10
✅	quality_gate_idle	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_idle	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_idle_all_features	intake_connections	10/10	bounds checks dashboard
❌	quality_gate_idle_all_features	memory_usage	9/10	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_logs	lost_bytes	10/10	bounds checks dashboard
✅	quality_gate_logs	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_metrics_logs	cpu_usage	10/10	bounds checks dashboard
✅	quality_gate_metrics_logs	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_metrics_logs	lost_bytes	10/10	bounds checks dashboard
✅	quality_gate_metrics_logs	memory_usage	10/10	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".

CI Pass/Fail Decision

❌ Failed. Some Quality Gates were violated.

• quality_gate_idle_all_features, bounds check memory_usage: 9/10 replicas passed. Failed 1 which is > 0. Gate FAILED.
• quality_gate_idle_all_features, bounds check intake_connections: 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 lost_bytes: 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 intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check lost_bytes: 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.

[davidor]

This still applies right? At least with the old formula.

[zhuminyi]

yes, deleted by mistake.

[davidor]

I think we should include the link. It's not obvious which repo you're referring to.

[zhuminyi]

/merge

[dd-devflow-routing-codex]

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[zhuminyi]

/merge

[dd-devflow-routing-codex]

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