Re: Applications using fsync cause hangs for several seconds every few minutes

[Andrew Guertin <andrew.guertin@uvm.edu>]

On 08/17/2011 10:41 PM, Anand Jain wrote:
> Dave,
>
> good to have a test case on the 3.0 kernel. do you have btrfs as
> root fs ? and
> can you show how are you using the btrfs mainly I would need
> 'btrfs fi show' let me try if I can reproduce.
>
> Thanks, Anand

Personally, I find that large compiles are very "useful" in making the issue 
occur sooner. I'm on gentoo, so when I was bisecting, I'd often just emerge 
openoffice and let it run for a while.

For observing, the best way I found was to run JOSM (Java OpenStreetMap editor). 
Browsing around a map is very interactive, so it's immediately noticeable when 
it hangs, and downloading map tiles all the time uses a lot of IO. In-browser 
map applications would probably work too.

My filesystem is partitioned with a small ext2 /boot as sda1, a 2GB swap as 
sda2, and the remaining space as btrfs / on sda3.
btrfs fi show gives:
Label: none  uuid: 28559ad8-7db8-402b-a93d-27ec9c5e943b
	Total devices 1 FS bytes used 102.83GB
	devid    1 size 144.90GB used 144.90GB path /dev/sda3

Btrfs v0.19-35-g1b444cd-dirty

--Andrew