[Bug]: Landing Page, System. on FreeBSD, the CPU frequency shows NaN GHz

[rickhull]

Bug description

Summary

CPU frequency displays as "NaN GHz" on the netdata landing page (System tab) on FreeBSD, despite the FreeBSD plugin successfully collecting CPU frequency data for charting.

Environment

• OS: FreeBSD 15.0-RELEASE (amd64)
• Netdata Version: v2.6.3
• CPU: Intel Pentium N3700 @ 1.60GHz
• Installation: FreeBSD pkg/ports (custom)
• Plugin: freebsd.plugin

Expected Behavior

The landing page System tab should display the current CPU frequency in GHz, e.g., "0.88 GHz" or "1.60 GHz".

Actual Behavior

The landing page displays "NaN GHz" for CPU frequency.

Expected behavior

Show the CPU frequency in numeric terms

Steps to reproduce

1. Run FreeBSD
2. Install NetData
3. Navigate to http://HOST:19999/
4. Click System at the bottom
5. Observe CPU frequency

Screenshots

Error Logs

No response

Desktop

OS: Windows
Browser Firefox
Browser Version [e.g. 22] 146.0.1

Additional context

No response

[rickhull]

Evidence

1. CPU Frequency Data is Available via sysctl

root@gw:~ # sysctl dev.cpu.0.freq
dev.cpu.0.freq: 880

root@gw:~ # sysctl dev.cpu | grep freq
dev.cpu.3.freq: 480
dev.cpu.2.freq: 480
dev.cpu.1.freq: 480
dev.cpu.0.freq: 880

2. Netdata Collector is Running

The freebsd.plugin is actively collecting CPU frequency data:

{
    "plugin": "freebsd.plugin",
    "module": "dev.cpu.0.freq"
}

3. Time-Series Chart Works Correctly

The chart cpu.scaling_cur_freq exists and contains valid data:

"cpu.scaling_cur_freq": {
    "id": "cpu.scaling_cur_freq",
    "name": "cpu.scaling_cur_freq",
    "type": "cpu",
    "family": "cpufreq",
    "context": "cpu.scaling_cur_freq",
    "title": "Current CPU Scaling Frequency (cpu.scaling_cur_freq)",
    "priority": 1002,
    "plugin": "freebsd.plugin",
    "module": "dev.cpu.0.freq",
    "units": "MHz",
    "dimensions": {
        "frequency": {
            "name": "frequency"
        }
    }
}

This chart displays correctly and shows valid frequency values when accessed via /api/v1/data?chart=cpu.scaling_cur_freq.

4. Metadata API Returns "unknown"

The /api/v1/info endpoint (used by the landing page) shows:

{
    "cpu_freq": "unknown",
    "host_labels": {
        "_system_cpu_freq": "unknown"
    }
}

The landing page attempts to render the string "unknown" as a numeric value, resulting in "NaN GHz".

Root Cause Analysis

The FreeBSD plugin has two separate code paths:

1. Time-series data collection (working): Reads dev.cpu.0.freq sysctl and creates charts ✅
2. Metadata population (broken): Should populate cpu_freq field in host info but returns "unknown" ❌

The metadata field is never populated with the actual CPU frequency value, despite being successfully collected for charting purposes.

Steps to Reproduce

1. Install netdata v2.6.3 on FreeBSD 15.0-RELEASE
2. Ensure dev.cpu.0.freq sysctl exists and returns valid data
3. Navigate to netdata landing page (port 19999 or via reverse proxy)
4. Click "System" tab at bottom of landing page
5. Observe "CPU Frequency" field displays "NaN GHz"
6. Verify chart works: access /api/v1/data?chart=cpu.scaling_cur_freq shows valid data

Expected Fix

The freebsd.plugin should populate the cpu_freq metadata field in /api/v1/info with the current CPU frequency value (e.g., "880" or "0.88" depending on expected format) when it successfully collects this data for charting.

Workaround

None. The issue is cosmetic - all charts function correctly. Users can ignore the "NaN GHz" display on the landing page.

Additional Notes

• This may affect other FreeBSD systems where dev.cpu.N.freq sysctl exists
• The related dev.cpu.temperature sysctl genuinely doesn't exist on this hardware (expected)
• System has 4 CPU cores, all reporting valid frequency data via sysctl