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Date:      Fri, 28 Sep 2018 14:32:44 +0930
From:      Shane Ambler <FreeBSD@ShaneWare.Biz>
To:        Rebecca Cran <rebecca@bluestop.org>, FreeBSD Current <freebsd-current@freebsd.org>
Subject:   Re: 12.0-ALPHA5 - ZFS default ARC max apparently forcing system to run out of memory
Message-ID:  <98b09476-ccd3-7449-0a52-3b0069b435b9@ShaneWare.Biz>
In-Reply-To: <f3267619-8706-47d2-7b07-590937bf4df7@bluestop.org>
References:  <f3267619-8706-47d2-7b07-590937bf4df7@bluestop.org>

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On 28/9/18 7:31 am, Rebecca Cran wrote:
> I'm running 12.0-ALPHA5 on a laptop which has 32GB RAM and 2GB swap.
> I've found it running out of memory when building ports via synth: I
> think I've also seen it when running a buildworld. Johannes on
> FreeBSDDesktop suggested it might be related to ZFS, and setting
> vfs.zfs.arc_max to 8GB *does* appear to have resolved the problem.
> 
> 
> Shortly after running out of memory (with |"swap_pager_getswapspace(32):
> failed" messages)|, the first few lines of 'top' were:

I believe the default arc settings are wrong, arc_max defaults to 1G
less than ram, with arc being wired this collides with other ram that
may be wired, by default the kernel is allowed to wire 30% of ram which
is in addition of any arc allocation. So arc should remain less than 70%
of ram.

I submitted bug 229764 with this.

Also consider any bhyve usage, the -S option will wire guest ram, which
one of the bhyve tools enables  as default.


-- 
FreeBSD - the place to B...Software Developing

Shane Ambler




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