Re: 12.0-ALPHA5 - ZFS default ARC max apparently forcing system to run out of memory

From: Shane Ambler <FreeBSD_at_ShaneWare.Biz>
Date: Fri, 28 Sep 2018 14:32:44 +0930
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
Received on Fri Sep 28 2018 - 03:03:00 UTC

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