Juju worker (k8s): disk usage analysis problem?

Hi all,

we are investigating disk usage in our juju k8s cluster and we found this folder in our juju worker node:

/var/lib/containerd/io.containerd.snapshotter.v1.overlayfs/snapshots

this folder uses over 100GB of disk space (our juju cluster is running Gitlab runner).
We found over 10k folders there created over 2-3 months ago.
What is this folder for ? And is there is any automatic way to purge it ?