[ZFS] refquota is very slow !

[InterNetX - Juergen Gotteswinter]

any special reason for disabling secondarycache and limiting the
primarycache to metadata? does it change something when you revert it to
default?

compression -> lz4, even if its not compressable, it wont hurt

you probably got several smaller performance issues which end up in this
mess all together.

Am 04.09.2016 um 17:16 schrieb Ben RUBSON:
> Same kind of results with a single local (SSD) disk based pool, refquota takes much more time than quota around the limit.
> 
> Here is the output for this single disk based pool :
> zfs get all   : http://pastebin.com/raw/TScgy0ps
> zdb           : http://pastebin.com/raw/BxmQ4xNx
> zpool get all : http://pastebin.com/raw/XugMbydy
> 
> Thank you !
> 
> Ben
> 
> 
>> On 04 Sep 2016, at 13:42, InterNetX - Juergen Gotteswinter <juergen.gotteswinter at internetx.com> wrote:
>>
>> Did you try the same in a single local disk based pool? And pls post output of
>> zfs get all, zdb & zpool get all
>>
>>
>>> Ben RUBSON <ben.rubson at gmail.com> hat am 4. September 2016 um 11:28
>>> geschrieben:
>>>
>>>
>>> Juergen & Bram,
>>>
>>> Thank you for your feedback.
>>>
>>> I then investigated further and think I found the root cause.
>>>
>>> No issue with refquota in my zroot pool containing (in this example) 300.000
>>> inodes used.
>>>
>>> However, refquota is terribly slow in my data pool containing around
>>> 12.000.000 inodes used.
>>>
>>> I then created 12.000.000 empty file in my zroot pool, in a test dataset.
>>> I put a refquota on this dataset and created a dd file to fulfil empty space.
>>> And around the limit, it began to stall...
>>> I then created an empty dataset in the same pool, refquota is even slow in
>>> this dataset having no inode used.
>>> The root cause seems then to be the total number of inodes used in the pool...
>>>
>>> Some numbers :
>>> Time to fulfil 512MB with quota : 17s
>>> Time to fulfil 512MB with refquota : 3m35s
>>>
>>> Very strange.
>>>
>>> Do you experience the same thing ?
>>>
>>> Thank you again,
>>>
>>> Ben
>>>
>>>> On 03 Sep 2016, at 16:59, Bram Vandoren <bram.vandoren at kuleuven.be> wrote:
>>>>
>>>> I encountered the same problem over NFS. I didn't manage to reproduce it not
>>>> using NFS. I think the userquota property works without any problem though.
>>>>
>>>> Cheers,
>>>> Bram.
>>>
>>>> On 03 Sep 2016, at 12:26, InterNetX - Juergen Gotteswinter
>>>> <juergen.gotteswinter at internetx.com> wrote:
>>>>
>>>> cant confirm this, works like a charm without difference to normal quota
>>>> setting
>>>
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