Re: extremely slow syncing on btrfs with 2.6.39.1

[Jan Stilow <jstilow@mobileobjects.de>]

On 07/11/2011 02:18 AM, Kok, Auke-jan H wrote:
> I've been monitoring the lists for a while now but didn't see this
> problem mentioned in particular: I've got a fairly standard desktop
> system at home, 700gb WD drive, nothing special, with 2 btrfs
> filesystems and some snapshots. The system runs for days, and I've
> noticed unusual disk activity the other evening - turns out that it's
> taking forever to sync().
> 
> $ uname -r
> 2.6.39.1
> $ grep btrfs /proc/mounts
> /dev/root / btrfs rw,relatime 0 0    # is /dev/sdb2 #
> /dev/sdb5 /home btrfs rw,relatime 0 0
> $ time sync
> 
> real	1m5.552s
> user	0m0.000s
> sys	0m2.102s
> 
> $ time sync
> 
> real	1m16.830s
> user	0m0.001s
> sys	0m1.490s
> 
> $ df -h / /home
> Filesystem      Size  Used Avail Use% Mounted on
> /dev/root        47G   33G  7.7G  82% /
> /dev/sdb5       652G  216G  421G  34% /home
> $ btrfs fi df /
> Data: total=35.48GB, used=29.86GB
> System, DUP: total=16.00MB, used=12.00KB
> System: total=4.00MB, used=0.00
> Metadata, DUP: total=4.50GB, used=1.67GB
>  $ btrfs fi df /home
> Data: total=310.01GB, used=209.53GB
> System, DUP: total=8.00MB, used=48.00KB
> System: total=4.00MB, used=0.00
> Metadata, DUP: total=11.00GB, used=2.98GB
> Metadata: total=8.00MB, used=0.00
> 
> I'll switch to 3.0 soon, but, given the fact that we're going to be
> running MeeGo on 2.6.39 probably for a while, I was wondering if
> anyone knows off the top of their heads if this issue is
> known/identified. If not then I'll need to make someone do some
> patching ;).
> 
> Auke

You should read the thread "Abysmal Performance" of these mailing list
from last month. They had a similar problem and downgraded to a 2.6.38
kernel. By the way, that works for me too for the time being.

Best Regards.

Jan Stilow