windows_exporter/internal/collector/system/AGENTS.md

system collector

The collector reads the single-instance PDH object System with pdh.CounterTypeRaw. The object exists on every Windows host, so no role is needed. The boot time comes from ntdll, not from the PDH counter System Up Time. These notes were recorded on Windows Server 2025 (build 26100).

• Context Switches/sec, Exception Dispatches/sec and System Calls/sec are PERF_COUNTER_COUNTER. The raw value is a cumulative count since boot. The type has a 32-bit raw value, so a busy host wraps it at 2^32; a scraper sees the wrap as a counter reset. System Calls/sec was already 345 million in the sample.
• Processes, Threads and Processor Queue Length are PERF_COUNTER_RAWCOUNT gauges. The help text calls Processes and Threads instantaneous counts. Processor Queue Length counts ready threads in the single queue shared by all processors, so per-processor load needs a division by the processor count. It was 0 in the sample.

Counter reference

Recorded on Windows Server 2025 (build 26100). Raw and Base are the first and second values that pdh.CounterTypeRaw returns for the sample instance.

System

Single-instance.

Counters the collector reads:

Counter	Type	Raw	Base
Context Switches/sec	PERF_COUNTER_COUNTER	50992231
Exception Dispatches/sec	PERF_COUNTER_COUNTER	321946
Processes	PERF_COUNTER_RAWCOUNT	200
Processor Queue Length	PERF_COUNTER_RAWCOUNT	0
System Calls/sec	PERF_COUNTER_COUNTER	345210165
Threads	PERF_COUNTER_RAWCOUNT	2894

Not read by the collector:

• PERF_COUNTER_BULK_COUNT: File Control Bytes/sec, File Read Bytes/sec, File Write Bytes/sec
• PERF_COUNTER_COUNTER: Alignment Fixups/sec, File Control Operations/sec, File Data Operations/sec, File Read Operations/sec, File Write Operations/sec, Floating Emulations/sec
• PERF_ELAPSED_TIME: System Up Time
• PERF_RAW_FRACTION: % Registry Quota In Use