windows_exporter/internal/collector/cache/AGENTS.md

cache collector

The collector reads the single-instance PDH object Cache (file system cache) 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).

• Every PERF_COUNTER_COUNTER (/sec) counter is a cumulative count since boot. In the sample, each Sync ... plus Async ... pair adds up exactly to its total: Copy Reads/sec, Data Maps/sec, Fast Reads/sec, MDL Reads/sec and Pin Reads/sec.
• The four ... Hits % counters are PERF_SAMPLE_FRACTION. The raw value is the cumulative hit count, not a percentage. The base (,secondvalue) is the cumulative count of attempts and equals the raw value of the matching /sec counter: Copy Read Hits % with Copy Reads/sec, Data Map Hits % with Data Maps/sec, MDL Read Hits % with MDL Reads/sec and Pin Read Hits % with Pin Reads/sec. The hit ratio is rate(raw) / rate(base).
• Data Map Pins/sec is also PERF_SAMPLE_FRACTION, despite its name. Its raw value is the cumulative count of data maps that pinned a page; its base is Data Maps/sec.
• Data Flushes/sec and Lazy Write Flushes/sec count write operations; Data Flush Pages/sec and Lazy Write Pages/sec count pages. One operation can move more than one page.
• Dirty Pages and Dirty Page Threshold are gauges in pages, not bytes.
• Async Fast Reads/sec, Async MDL Reads/sec and Fast Read Resource Misses/sec stayed 0 on this host.

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.

Cache

Single-instance.

Counters the collector reads:

Counter	Type	Raw	Base
Async Copy Reads/sec	PERF_COUNTER_COUNTER	35778
Async Data Maps/sec	PERF_COUNTER_COUNTER	2
Async Fast Reads/sec	PERF_COUNTER_COUNTER	0
Async MDL Reads/sec	PERF_COUNTER_COUNTER	0
Async Pin Reads/sec	PERF_COUNTER_COUNTER	12297
Copy Read Hits %	PERF_SAMPLE_FRACTION	1607787	3347074
Copy Reads/sec	PERF_COUNTER_COUNTER	3347074
Data Flush Pages/sec	PERF_COUNTER_COUNTER	9099373
Data Flushes/sec	PERF_COUNTER_COUNTER	655879
Data Map Hits %	PERF_SAMPLE_FRACTION	67204750	67331258
Data Map Pins/sec	PERF_SAMPLE_FRACTION	12144215	67331258
Data Maps/sec	PERF_COUNTER_COUNTER	67331258
Dirty Page Threshold	PERF_COUNTER_LARGE_RAWCOUNT	2097010
Dirty Pages	PERF_COUNTER_LARGE_RAWCOUNT	175
Fast Read Not Possibles/sec	PERF_COUNTER_COUNTER	206860
Fast Read Resource Misses/sec	PERF_COUNTER_COUNTER	0
Fast Reads/sec	PERF_COUNTER_COUNTER	2861445
Lazy Write Flushes/sec	PERF_COUNTER_COUNTER	276157
Lazy Write Pages/sec	PERF_COUNTER_COUNTER	5836457
MDL Read Hits %	PERF_SAMPLE_FRACTION	1958	1959
MDL Reads/sec	PERF_COUNTER_COUNTER	1959
Pin Read Hits %	PERF_SAMPLE_FRACTION	3216022	3671006
Pin Reads/sec	PERF_COUNTER_COUNTER	3671006
Read Aheads/sec	PERF_COUNTER_COUNTER	2012322
Sync Copy Reads/sec	PERF_COUNTER_COUNTER	3311296
Sync Data Maps/sec	PERF_COUNTER_COUNTER	67331256
Sync Fast Reads/sec	PERF_COUNTER_COUNTER	2861445
Sync MDL Reads/sec	PERF_COUNTER_COUNTER	1959
Sync Pin Reads/sec	PERF_COUNTER_COUNTER	3658709