Hi On Tue, Aug 5, 2014 at 4:37 PM, Oon-Ee Ng <ngoonee.talk@xxxxxxxxx> wrote: > Yesterday night I noticed (just before performing an update my conky > showing high continuous writing to root. iotop -Pa shows this:- > > Total DISK READ : 0.00 B/s | Total DISK WRITE : 8.93 M/s > Actual DISK READ: 0.00 B/s | Actual DISK WRITE: 11.06 M/s > PID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND > 112 be/4 root 0.00 B 64.91 M 0.00 % 24.34 % [kworker/u16:3] > 11936 be/4 root 0.00 B 0.00 B 0.00 % 0.06 % [kworker/1:1] > 28794 be/4 root 0.00 B 36.00 K 0.00 % 0.00 % [kworker/u16:1] > > This is after roughly 6-7 seconds, and 65 MB has already been written > by that kworker thread. How long this IO activity takes? Could it be some kind of automatic defragmentation or some other internal btrfs background optimization? A good idea is to check btrfs changelog for 3.16 kernel release. > > As I said, this was already happening before an upgrade. I ran the > upgrade anyway, which upgraded linux to 3.16-2, and still got the same > thing. Yes, I'm using [testing]. > > Any ideas on how to proceed? Next thing I'm going to try is > downgrading linux to 3.15, but I thought I'd post this here first in > case I don't make it back. 'perf' is a great and very powerful tool that allow to debug problems like this. Run '# perf top -g -p $PID' and it will show where the process spends *cpu cycles*. It should be enough to understand what kworker thread does. For all curious minds I highly recommend to read this tutorial https://perf.wiki.kernel.org/index.php/Tutorial
