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Date:      Mon, 25 Apr 2022 15:27:27 +0200
From:      Alexander Leidinger <Alexander@leidinger.net>
To:        Doug Ambrisko <ambrisko@ambrisko.com>
Cc:        Mateusz Guzik <mjguzik@gmail.com>, freebsd-current@freebsd.org, pstef@freebsd.org
Subject:   Re: nullfs and ZFS issues
Message-ID:  <20220425152727.Horde.YqhquyTW0ZM3HAbI1kyskic@webmail.leidinger.net>
In-Reply-To: <20220424195817.Horde.W5ApGT13KmR06W2pKA0COxB@webmail.leidinger.net>
References:  <Yl31Frx6HyLVl4tE@ambrisko.com> <20220420113944.Horde.5qBL80-ikDLIWDIFVJ4VgzX@webmail.leidinger.net> <YmAy0ZNZv9Cqs7X%2B@ambrisko.com> <20220421083310.Horde.r7YT8777_AvGU_6GO1cC90G@webmail.leidinger.net> <CAGudoHEyCK4kWuJybD4jzCHbGAw46CQkPx_yrPpmRJg3m10sdQ@mail.gmail.com> <20220421154402.Horde.I6m2Om_fxqMtDMUqpiZAxtP@webmail.leidinger.net> <YmGIiwQen0Fq6lRN@ambrisko.com> <20220422090439.Horde.TabULDW9aIeaNLxngZxdvvN@webmail.leidinger.net> <20220424195817.Horde.W5ApGT13KmR06W2pKA0COxB@webmail.leidinger.net>

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Quoting Alexander Leidinger <Alexander@leidinger.net> (from Sun, 24=20=20
Apr=202022 19:58:17 +0200):

> Quoting Alexander Leidinger <Alexander@leidinger.net> (from Fri, 22=20=20
>=20Apr 2022 09:04:39 +0200):
>
>> Quoting Doug Ambrisko <ambrisko@ambrisko.com> (from Thu, 21 Apr=20=20
>>=202022 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=20=
=20
>>=20using nocache in the nightly periodic runs. 4h instead of 12-24h=20=20
>>=20(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=20=20
>>=20nocache and reduced arc reclaim settings (100, 1). I will check the=20=
=20
>>=20runtime for the next 2 days.
>
> 9-10h runtime with the above settings (compared to 4h with nocache=20=20
>=20and 12-24h without any patch and without nocache).
> I changed the sysctls back to the defaults and will see in the next=20=20
>=20run (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=20=20
periodic=20daily run of those 22 jails in the state "*vnode"). Seems=20=20
nocache=20gives the best perf for me in this case.

Bye,
Alexander.

--=20
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http://www.FreeBSD.org    netchild@FreeBSD.org  : PGP 0x8F31830F9F2772BF

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