Hi guys, We are facing some issues with a btrfs filesystem on one of our department filers. The problem started pretty much one week ago, when I decided to purge old snapshots. Until then we were doing daily btrfs snapshots to have a quick backup. What then happened was that btrfs-cleaner kicked in, and is now slowing things down very badly. It is consuming 100% CPU and also a lot of IOP/s. I tried reducing its CPU priority, but that was pretty much without effect. Beside that we tried restarting the machine, but that also did not mitigate the problem. I understand that purging snapshots is a complex operation, but we somehow need to reduce the load this causes during working hours. Are there any ways to tell btrfs-cleaner to suspend or reduce its operations? Background: The file-server runs inside a XEN domU The backing disk is a Ceph RDB with 50TiB capacity We employ a bcache with a local SSD to improve latency Files are served via NFS and Samba to a couple of hundred clients. Thanks & regards Simon uname -a Linux v2-fs 4.1.42-xen #2 SMP Wed Jul 12 14:06:37 CEST 2017 x86_64 GNU/Linux btrfs --version Btrfs v3.17 btrfs fi show Label: 'v2-fs-data' uuid: f2bad13d-8b02-4325-8c4a-31b0cafb1549 Total devices 1 FS bytes used 6.98TiB devid 1 size 50.00TiB used 7.48TiB path /dev/bcache0 Btrfs v3.17 btrfs fi df /mnt/ceph/ Data, single: total=7.10TiB, used=6.93TiB System, DUP: total=8.00MiB, used=864.00KiB System, single: total=4.00MiB, used=0.00B Metadata, DUP: total=194.00GiB, used=54.93GiB Metadata, single: total=8.00MiB, used=0.00B GlobalReserve, single: total=512.00MiB, used=0.00B dmesg did not contain any recent (2 days) events. The older ones were about NFSd being stuck for more than 30 seconds while reading from disk. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
