fragmentation¶

Default Metrics¶

The following metrics are emitted by default. Each of them can be disabled by applying the following configuration:

metrics:
  <metric_name>:
    enabled: false

fscache.extents.max¶

Highest extent count of any single FS-Cache backing file. SEEK_HOLE cost in the cachefiles read path is proportional to this value.

Unit	Metric Type	Value Type	Stability
{extents}	Gauge	Int	Alpha

fscache.extents.mean_bytes¶

Mean extent length across all FS-Cache backing files. A value below the NFS rsize indicates cache writes are not coalescing into larger extents.

Unit	Metric Type	Value Type	Stability
By	Gauge	Int	Alpha

fscache.extents.unwritten_bytes¶

Disk capacity allocated to FS-Cache backing files in unwritten extents, holding no cached data yet. XFS pads each allocation up to the extent size hint and marks the surplus unwritten, so this is the capacity CACHEFILESD_EXTSIZE has reserved ahead of use. Consumed as backing files fill. Zero when the hint is disabled.

Unit	Metric Type	Value Type	Stability
By	Gauge	Int	Alpha

fscache.fragmentation.scrape_duration¶

Time taken to scan FS-Cache and collect extent statistics. Use this to tune the collection_interval; keep the duration well below the interval.

Unit	Metric Type	Value Type	Stability
ms	Gauge	Int	Alpha