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Date:      Tue, 2 Jul 2019 12:13:48 -0400
From:      Mike Tancsa <mike@sentex.net>
To:        "Nagy, Attila" <bra@fsn.hu>, freebsd-fs@FreeBSD.org
Subject:   Re: ZFS exhausts kernel memory just by importing zpools
Message-ID:  <820ceee3-95aa-9925-066d-5d22884ce001@sentex.net>
In-Reply-To: <e542dfd4-9534-1ec7-a269-89c3c20cca1d@fsn.hu>
References:  <e542dfd4-9534-1ec7-a269-89c3c20cca1d@fsn.hu>

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On 7/2/2019 10:58 AM, Nagy, Attila wrote:
> Hi,
>
> Running latest stable/12 on amd64 with 64 GiB memory on a machine with
> 44 4T disks. Each disks have its own zpool on it (because I solve the
> redundancy between machines and not locally with ZFS).
>
> One example zpool holds 2.2 TiB of data (according to df) and have
> around 75 million files in hashed directories, this is the typical
> usage on them.
>
> When I import these zpools, top says around 50 GiB wired memory (ARC
> is minimal, files weren't yet touched) and after I start to use (heavy
> reads/writes) the pools, the free memory quickly disappears (ARC
> grows) until all memory is gone and the machine starts to kill
> processes, ends up in a deadlock, where nothing helps.
>
> If I import the pools one by one, each of them adds around 1-1.5 GiB
> of wired memory. 

Hi,

    You mean you have 44 different zpools ?  75mil files per pool sounds
like a lot. I wonder for testing purposes, you made 1 or two zpools with
44 (or 22) different datasets and had 3.3billion files, would you run
into the same memory exhaustion ?

    ---Mike




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