On Fri, 28 Jul 2017 17:40:50 +0100 (BST)
"Konstantin V. Gavrilenko" <k.gavrile...@arhont.com> wrote:

> Hello list, 
> 
> I am stuck with a problem of btrfs slow performance when using compression.
> 
> when the compress-force=lzo mount flag is enabled, the performance drops to 
> 30-40 mb/s and one of the btrfs processes utilises 100% cpu time.
> mount options: btrfs 
> relatime,discard,autodefrag,compress=lzo,compress-force,space_cache=v2,commit=10

It does not work like that, you need to set compress-force=lzo (and remove
compress=).

With your setup I believe you currently use compress-force[=zlib](default),
overriding compress=lzo, since it's later in the options order.

Secondly,

> autodefrag

This sure sounded like a good thing to enable? on paper? right?...

The moment you see anything remotely weird about btrfs, this is the first
thing you have to disable and retest without. Oh wait, the first would be
qgroups, this one is second.

Finally, what is the reasoning behind "commit=10", and did you check with the
default value of 30?

-- 
With respect,
Roman
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