Hi Sage,

I did some testing with btrfs-unstable yesterday. With the recent
commit from Chris it looks quite good:

"Btrfs: force unplugs when switching from high to regular priority bios=
"


However I can't test it extensively, because our main environment is
on ext4 at the moment.

Regards
Christian

2011/8/8 Sage Weil [off-list ref]:

Hi Christian,

Are you still seeing this slowness?

sage


On Wed, 27 Jul 2011, Christian Brunner wrote:

quoted

2011/7/25 Chris Mason [off-list ref]:

quoted

Excerpts from Christian Brunner's message of 2011-07-25 03:54:47 -=

0400:

quoted

quoted

quoted

Hi,

we are running a ceph cluster with btrfs as it's base filesystem
(kernel 3.0). At the beginning everything worked very well, but a=

fter

quoted

quoted

quoted

a few days (2-3) things are getting very slow.

When I look at the object store servers I see heavy disk-i/o on t=

he

quoted

quoted

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btrfs filesystems (disk utilization is between 60% and 100%). I a=

lso

quoted

quoted

quoted

did some tracing on the Cepp-Object-Store-Daemon, but I'm quite
certain, that the majority of the disk I/O is not caused by ceph =

or

quoted

quoted

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any other userland process.

When reboot the system(s) the problems go away for another 2-3 da=

ys,

quoted

quoted

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but after that, it starts again. I'm not sure if the problem is
related to the kernel warning I've reported last week. At least t=

here

quoted

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is no temporal relationship between the warning and the slowdown.

Any hints on how to trace this would be welcome.

The easiest way to trace this is with latencytop.

Apply this patch:

http://oss.oracle.com/~mason/latencytop.patch

And then use latencytop -c for a few minutes while the system is s=

low.

quoted

quoted

Send the output here and hopefully we'll be able to figure it out.

I've now installed latencytop. Attached are two output files: The
first is from yesterday and was created aproxematly half an hour aft=

er

quoted

the boot. The second on is from today, uptime is 19h. The load on th=

e

quoted

system is already rising. Disk utilization is approximately at 50%.

Thanks for your help.

Christian

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