Re: nullfs and ZFS issues

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.

Bye,
Alexander.
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