windows_exporter/internal/collector/cpu/AGENTS.md

cpu collector

The collector reads the multi-instance PDH object Processor Information with pdh.CounterTypeRaw. The object exists on every Windows host, so no role is needed. These notes were recorded on Windows Server 2025 (build 26100), a Hyper-V guest with 12 logical processors in one processor group.

• Instances are <group>,<processor>, for example 0,0 to 0,11. Besides _Total the object has one aggregate per processor group, <group>,_Total (here 0,_Total). pdh.IsTotalInstance treats both as totals, so with pdh.InstancesAll they are dropped and only per-processor rows remain. The core label is the raw instance name, e.g. 0,3.
• % C1/C2/C3 Time, % DPC Time, % Idle Time, % Interrupt Time, % Privileged Time and % User Time are PERF_100NSEC_TIMER. Their raw value is cumulative 100 ns ticks; internal/pdh scales them to seconds.
• % Processor Time and % Priority Time are PERF_100NSEC_TIMER_INV. The raw value is cumulative idle (non-busy) time in 100 ns ticks, not busy time, and internal/pdh does not scale this type to seconds. In the sample, the raw value of % Processor Time equals % Idle Time.
• % Processor Utility, % Processor Performance and % Privileged Utility are PERF_AVERAGE_BULK. Raw and base are both cumulative. The displayed value is delta raw / delta base and is already a percentage (it can exceed 100). A 2 s sample on core 0,0 gave 63.4 for utility and 121.9 for performance. The raw values of utility and performance are almost equal; their bases differ. % Processor Utility and % Privileged Utility have nearly equal bases that grew about 630 000 per second; the performance base grew about 330 000 per second.
• Interrupts/sec, DPCs Queued/sec and Clock Interrupts/sec (PERF_COUNTER_COUNTER) and C1/C2/C3 Transitions/sec, Idle Break Events/sec (PERF_COUNTER_BULK_COUNT) are cumulative counts.
• Processor Frequency is a gauge in MHz (3700 here). Parking Status is a gauge, 0 when the processor is not parked. % Performance Limit is a gauge percentage (100 here). % C3 Time and C3 Transitions/sec stayed 0 on this virtual machine.

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.

Processor Information

Multi-instance. Instances: _Total, 0,_Total, 0,0, 0,1, 0,10, 0,11, 0,2, 0,3, ... (14 in total). Sample instance: 0,0.

Counters the collector reads:

Counter	Type	Raw	Base
% C1 Time	PERF_100NSEC_TIMER	3366958649
% C2 Time	PERF_100NSEC_TIMER	21091589064
% C3 Time	PERF_100NSEC_TIMER	0
% DPC Time	PERF_100NSEC_TIMER	185312500
% Idle Time	PERF_100NSEC_TIMER	25109218750
% Interrupt Time	PERF_100NSEC_TIMER	257812500
% Performance Limit	PERF_COUNTER_RAWCOUNT	100
% Priority Time	PERF_100NSEC_TIMER_INV	26964687500
% Privileged Time	PERF_100NSEC_TIMER	4745937500
% Privileged Utility	PERF_AVERAGE_BULK	35875675583	2142017948
% Processor Performance	PERF_AVERAGE_BULK	80044724120	669031135
% Processor Time	PERF_100NSEC_TIMER_INV	25109218750
% Processor Utility	PERF_AVERAGE_BULK	80044725697	2142017679
% User Time	PERF_100NSEC_TIMER	4394687500
C1 Transitions/sec	PERF_COUNTER_BULK_COUNT	2303708
C2 Transitions/sec	PERF_COUNTER_BULK_COUNT	2337838
C3 Transitions/sec	PERF_COUNTER_BULK_COUNT	0
Clock Interrupts/sec	PERF_COUNTER_COUNTER	1571877
DPCs Queued/sec	PERF_COUNTER_COUNTER	561134
Idle Break Events/sec	PERF_COUNTER_BULK_COUNT	4641550
Interrupts/sec	PERF_COUNTER_COUNTER	7795204
Parking Status	PERF_COUNTER_RAWCOUNT	0
Processor Frequency	PERF_COUNTER_RAWCOUNT	3700

Not read by the collector:

• PERF_AVERAGE_BULK: Actual Frequency
• PERF_COUNTER_RAWCOUNT: % of Maximum Frequency, DPC Rate, Performance Limit Flags, Processor State Flags
• PERF_PRECISION_100NS_TIMER: Average Idle Time