btrfs consuming lots of sys cpu time

fblaise@snowball ~ $ ps -eo pcpu,pid,user,args | sort -k 1 -r | head -10
%CPU PID USER COMMAND
7.4 2591 root [flush-btrfs-1]
5.9 905 root [btrfs-endio-0]
4.4 2907 root [btrfs-endio-wri]
4.3 1314 root /usr/bin/X :0 vt7 -nr -nolisten tcp -auth /var/run/xauth/A:0-VjxI1a
2.7 900 root [btrfs-worker-0]
1.7 2106 fblaise /usr/bin/knotify4
1.4 2094 fblaise kwin
0.6 10 root [kworker/0:1]
0.5 3643 fblaise top

And it is only on my /home filesystem… system is currently sitting idle. Wow.

This is on a Linux Mint laptop with 3.0.0-13-generic-pae.

Anyone experienced this?