Date: Sat, 17 Feb 2018 20:27:19 -0800 From: Mark Millard <marklmi26-fbsd@yahoo.com> To: bob prohaska <fbsd@www.zefox.net> Cc: Freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: Pi3 out of swap at < 50% Message-ID: <926334BC-5FEE-4628-B958-9670351DA3D5@yahoo.com> In-Reply-To: <20180218003840.GD93736@www.zefox.net> References: <20180217162732.GA93736@www.zefox.net> <1518885801.91697.2.camel@freebsd.org> <9bf0ca6e-1916-3f4d-71fe-0515fe6a717f@zyxst.net> <20180218003840.GD93736@www.zefox.net>
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On 2018-Feb-17, at 4:38 PM, bob prohaska <fbsd at www.zefox.net> wrote:
> . . .
> On my RPI2 running armv7 it looks like the out of swap error is real:
> 2 GB are configured, around 1.5 GB are usable (limited by internal =
table
> sizes) and I see "out of swap" with about 1.5GB usage showing in top.
>=20
> . . .
If you are getting notices such as:
warning: total configured swap (524288 pages) exceeds maximum =
recommended amount (405460 pages).
then, quoting "man 8 loader" and its kern.maxswzone material,
Note that swap metadata can be fragmented, which means =
that
the system can run out of space before it reaches the
theoretical limit. Therefore, care should be taken to =
not
configure more swap than approximately half of the
theoretical maximum.
is what that warning is about: Looking at the swapon_check_swzone code =
the
warning is reporting the "half" figure as "recommended", not reporting =
the
theoretical maximum. So, translating: "care should be taken to not
configure more swap than" the reported maximum recommended amount. (If I
understand correctly.)
You might well be better off with around 1.5 GiBytes of swap than with 2
GiBytes of swap for an RPI2. (405460 pages is about 1.54 GiBytes.)
> The best part is that a Pi2 running 11.0 managed to build world and =
kernel
> using 256 MB of md99 swap. It was using j2, but that's the only =
difference.
> IIRC it took about three days.
The larger the -jN figure, the more swap is actually used at times. A =
good
test might be to try the old -j2 figure (or even -j1) and having about =
1.5
GiBytes of swap: find a combination that works and then explore =
variations
from that base-case.
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
( markmi at dsl-only.net is
going away in 2018-Feb, late)
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