cachefilesd

cachefilesd

This extension provides cachefilesd - the userspace daemon for FS-Cache, the Linux kernel filesystem caching facility. It ships both the cachefiles kernel module and the cachefilesd daemon.

FS-Cache allows network filesystems (NFS, Ceph, etc.) to cache data on local disk, dramatically reducing cold-start latency for read-heavy workloads. The cache is transparent: applications see no change in behavior, but repeated reads from the network filesystem are served from local disk instead.

Usage

The kernel module is not loaded automatically. Add cachefiles with KernelModuleConfig in your machine config:

apiVersion: v1alpha1
kind: KernelModuleConfig
name: cachefiles

The cachefilesd extension service starts automatically once /dev/cachefiles appears (i.e., the module is loaded) and the user has provided a configuration file (see below).

Configuration

Create a user volume which will serve as the cache location. Any user volume should work, e.g. using a partition or whole disk. If you want to share cache with EPHEMERAL, use directory type volume.

apiVersion: v1alpha1
kind: UserVolumeConfig
name: fscache
volumeType: partition
provisioning:
    diskSelector:
        match: disk.transport == "nvme" 
    maxSize: 50GiB

The extension ships no default config. The service waits until you provide /etc/cachefilesd.conf via EtcFileConfig, which is bind-mounted into the service container:

apiVersion: v1alpha1
kind: EtcFileConfig
name: cachefilesd.conf
mode: 0o644
contents: |
  dir /var/mnt/fscache
  tag mycache
  brun 10%
  bcull 7%
  bstop 3%
  frun 10%
  fcull 7%
  fstop 3%

Note: The dir line must point to a directory on a user volume fscache, so the value should be /var/mnt/fscache always, but the user volume backing it can be any user volume.

Enabling fscache on NFS mounts

To cache an NFS export, add fsc to the mount options. For a Kubernetes PVC backed by NFS, this is typically done in the CSI driver or storage class configuration. Adjust the dir line in the config above if a different cache location is needed.

Compatibility

Requires a Talos kernel built with CONFIG_FSCACHE=y and CONFIG_NFS_FSCACHE=y (if using NFS fscache). The cachefiles module (CONFIG_CACHEFILES=m) is provided by this extension.