btrfs advice?

[Michael Wiktowy]

On Mon, May 30, 2011 at 10:48 PM, Clyde E. Kunkel
<clydekunkel7734 at cox.net> wrote:
> On 05/30/2011 01:13 AM, Michael Wiktowy wrote:
>> <snip>
>>
>> 2) I see (using 'mount') that the root is btrfs along with some (what
>> appear to be) subvolumes for /tmp, /var/tmp and /home yet 'btrfs
>> device scan' shows no information. Does 'btrfs device scan' only scan
>> unmounted devices or is this a bug?
>><snip>
>
> try:
>
> $ sudo btrfs device scan
> $ dmesg | grep transid

This is a direct cut and paste:

[mwiktowy at netbook ~]$ sudo btrfs device scan
[sudo] password for mwiktowy:
Scanning for Btrfs filesystems
[mwiktowy at netbook ~]$ dmesg|grep transid
[    3.600235] device fsid 7a4812176077d1e2-369760c3b102cf84 devid 1
transid 1709 /dev/sda3
[    3.649785] device fsid 7a4812176077d1e2-369760c3b102cf84 devid 1
transid 1709 /dev/sda3
[    3.869158] device fsid 7a4812176077d1e2-369760c3b102cf84 devid 1
transid 1709 /dev/sda3
[ 9877.217727] device fsid 7a4812176077d1e2-369760c3b102cf84 devid 1
transid 1951 /dev/sda3

Nothing shows up with the btrfs tool but grepping the start up logs
reveals btrfs activity. I guess I will write a bug report and see what
comes of it.

To answer my own question 3) and somewhat 4):
I just added the compress=lzo option in fstab and that seems to work
without problems so far and grepping /var/log/messages indicates that
the kernel is using that flag. It doesn't seem to add all that much
CPU load from what I can tell ... what does add significant CPU load
is actually *viewing* the CPU load with System Monitor. It seems that
drawing a graph in screen in F15 is quite labour intensive. Heisenberg
uncertainly certainly applies with CPU load.

/Mike