Re: Bad fs performance, IO freezes

[Donald Pearson <donaldwhpearson@gmail.com>]

AFAIK quotas aren't a mount option, but if you never enabled them and
created the qgroups by hand that's your answer and the issue must be
something else.

On Mon, Oct 26, 2015 at 8:36 AM, cheater00 . <cheater00@gmail.com> wrote:
> There are no quotas. I haven't enabled them. I believe the fstab says
> that - could they be enabled in another way? How do I check for sure?
> The man page doesn't say how to check the status:
> https://btrfs.wiki.kernel.org/index.php/Manpage/btrfs-quota
>
> On Mon, Oct 26, 2015 at 2:32 PM, Donald Pearson
> <donaldwhpearson@gmail.com> wrote:
>> Accidentally didn't reply to the list the 1st time.
>>
>> I see the same issue when I have quotas enabled.  If you have quotas
>> on, see if turning them off helps.
>>
>> On Mon, Oct 26, 2015 at 7:16 AM, cheater00 . <cheater00@gmail.com> wrote:
>>> Hi guys,
>>> I am running into really bad performance. Here's my setup:
>>>
>>> WD Red 6 TB connected over USB2 to my core i7 laptop, running Ubuntu
>>> 32-bit with kernel 4.0.4-040004-generic #201505171336.
>>>
>>> Single btrfs partition covering whole disk.
>>>
>>> Autodefrag is on.
>>>
>>> fstab line:
>>> UUID=... /media/X btrfs rw,nosuid,nodev,autodefrag 0 0
>>>
>>> Sometimes when files are being modified or removed, I see
>>> btrfs-transacti eat 100% cpu; during this time no io operations
>>> succeed, that is, they're all stalled. You can't even ls on that fs.
>>> This happens for several minutes then normal operation resumes. There
>>> doesn't seem to be a rule to what will trigger this, other than
>>> opening a single file and reading usually works quite well. (say,
>>> watching a movie while all other programs are closed). But even moving
>>> files off the disks triggers some sort of bug. Just now I am moving a
>>> few files (just 30gb worth) onto another disk, and the bug triggers.
>>> So btrfs-transacti was eating my cpu for over 5 minutes and according
>>> to mv's output after this was done and cpu usage went back to normal
>>> what I was waiting for was for a tiny png file to be removed. This is
>>> pretty bad.
>>>
>>> I have tried defragmenting directories where files are being accessed
>>> and moved. This hasn't helped.
>>>
>>> This happens whether the FS is near full or not. It currently is near
>>> full but it wasn't before and it still did that. It still has about ~
>>> 100GB free space now.
>>>
>>> The more things are happening the more often this bug gets triggered.
>>> So if I have utorrent running and its temporary downloads directory is
>>> there, its download speed graph will be a few spikes of running at
>>> several MB/sec separated by durations of 0 download speed.
>>>
>>> Nothing seems to show up in dmesg or syslog.
>>>
>>> I have asked in #btrfs but the suggestions ended up not fixing the
>>> issue (autodefrag, defrag dirs).
>>>
>>> Please advise what I should do with this issue.
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