Re: nullfs and ZFS issues

Quoting Alexander Leidinger <Alexander@leidinger.net> (from Sun, 24  
Apr 2022 19:58:17 +0200):

> Quoting Alexander Leidinger <Alexander@leidinger.net> (from Fri, 22  
> Apr 2022 09:04:39 +0200):
>
>> Quoting Doug Ambrisko <ambrisko@ambrisko.com> (from Thu, 21 Apr  
>> 2022 09:38:35 -0700):
>
>>> I've attached mount.patch that when doing mount -v should
>>> show the vnode usage per filesystem.  Note that the problem I was
>>> running into was after some operations arc_prune and arc_evict would
>>> consume 100% of 2 cores and make ZFS really slow.  If you are not
>>> running into that issue then nocache etc. shouldn't be needed.
>>
>> I don't run into this issue, but I have a huge perf difference when  
>> using nocache in the nightly periodic runs. 4h instead of 12-24h  
>> (22 jails on this system).
>>
>>> On my laptop I set ARC to 1G since I don't use swap and in the past
>>> ARC would consume to much memory and things would die.  When the
>>> nullfs holds a bunch of vnodes then ZFS couldn't release them.
>>>
>>> FYI, on my laptop with nocache and limited vnodes I haven't run
>>> into this problem.  I haven't tried the patch to let ZFS free
>>> it's and nullfs vnodes on my laptop.  I have only tried it via
>>
>> I have this patch and your mount patch installed now, without  
>> nocache and reduced arc reclaim settings (100, 1). I will check the  
>> runtime for the next 2 days.
>
> 9-10h runtime with the above settings (compared to 4h with nocache  
> and 12-24h without any patch and without nocache).
> I changed the sysctls back to the defaults and will see in the next  
> run (in 7h) what the result is with just the patches.

And again 9-10h runtime (I've seen a lot of the find processes in the  
periodic daily run of those 22 jails in the state "*vnode"). Seems  
nocache gives the best perf for me in this case.

Bye,
Alexander.

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