Re: [branch:bcachefs-testing][tier] Massive slow down after some time

On Sun, Nov 06, 2016 at 03:04:12PM +0100, Marcin wrote:

Hi!
I'm trying mentioned branch. I've got tiered bcachefs witch lz4 compresion
turned on.
After some times of copying of files into bcachefs I noticed huge slow downa
of writing. Htop shows that kernel thread bcache_gc consumes a lot of CPU
and spends a lot of time waiting for I/O. Iostat shows that almost all
I/Ooperations goes to tier 1. In dmesg I see a couple of repeated messages
(they appears together, "INFO: task kworker/u8:2:11787 blocked for more than
120 seconds." with "INFO: task rsync:11935 blocked for more than 120
seconds." :

Sounds like tiering isn't freeing up space on tier 0... Can you check
cache0/alloc_debug (assuming cache0 is your tier 0 device) to confirm?

After that, could you hammer on single device mode for awhile? I need to know if
I'm just looking for tiering bugs, or if the btree changes have issues.