Delayed release of disk-space causes deletes of more snapshots that required.
It seems that script doesn't work as expected. If parameter --target-freespace is higher than current free space, it starts deleting old snapshots. But between deleting snapshot and real releasing of its space is some period of time - it may take many minutes before some space is released. Script is not waiting to it and immediately delete next snapshot, and so on. This is in function cleandir. I would fix it but I don't know how to determine if btrfs cleaner is currently cleaning after snapshot or not. Any workaround can be sleeping between deleting next snapshot. Kybl 19:49, 29 March 2011 (UTC)
I have not seen that problem on my system. I don't have any clue how to fix it other than your suggestion to delay between unlinks, and that doesn't really smell right :( --HelgeJensen 20:05, 29 March 2011 (UTC)
I have snapshot of whole filesystem, 200 GB allocated. When I delete snapshot, it takes 5 - 10 seconds before ANY disk activity and cca 3 minutes until btrfs-cleaner is done. Process btrfs-cleaner is running always. I don't know about any stats if cleaner is active or not. Kybl 21:31, 29 March 2011 (UTC)