On Mon, Oct 8, 2012 at 8:08 AM, Swâmi Petaramesh [off-list ref] wrote:

Le 08/10/2012 00:47, Goffredo Baroncelli a écrit :

quoted

Please could you clarify if you are using the "autodefrag" options
when you have the performance problem ?

I use autodefrag on all volumes systematically, except on volumes that I
use for really big files that would always be defragmenting (i.e.
virtual machines, but I seldom use virtual machines, and my performance
problem is general, I don't take VMs into consideration in this respect...)

The autodefrag option is per filesystem not per subvolume. The settings
of the first subvolueme is used also for the other ones.

So, because you mount the same filesystem both on

/dev/VG1/BTR_POOL    /    btrfs

subvol=UBUNTU/@,space_cache,autodefrag,compress=lzo,relatime        0 0

and

/dev/VG1/BTR_POOL    /data/VBOX_HIDDEN    btrfs

subvol=DATA/VBOX_HIDDEN,space_cache,compress=lzo,noatime    0 0

/dev/VG1/BTR_POOL    /data/VBOX_VMS        btrfs

subvol=DATA/VBOX_VMS,space_cache,compress=lzo,noatime    0 0

the autodefrag option is enabled also for DATA/VBOX_HIDDEN and DATA/VBOM_VMS

quoted

Are you in position to to reduce the number of snapshot from hundreds
to few  ?

I might do this as an experiment, but it would defeat one of the
prominent purposes for which I use BTRFS, and the number of snapshots
would grow immediately again, as I use the excellent OpenSuSE "snapper"
tool, that makes a snapshot every single hour...

I am not suggesting that as solution, but this would help to
investigate the problem.

If you don't have any needs of the snapshot, you can delete it, wait
that the cleaner
kernel thread does its job (it could require a bit of time), then
reboot the machine.
If I am right the performance should goes high.

I fear that both the combination of autodefrag and the high number of
snapshot could
be the root-cause of the the bad performance.

Kind regards.

Ciao
Goffredo

--
Swâmi Petaramesh [off-list ref] http://petaramesh.org PGP 9076E32E
Ne cherchez pas : Je ne suis pas sur Facebook.