Date: Sat, 4 Jan 2025 21:33:04 -0800 From: Chris Torek <chris.torek@gmail.com> To: Craig Leres <leres@freebsd.org> Cc: Karl Denninger <karl@denninger.net>, freebsd-hackers@freebsd.org Subject: Re: curious crashes when under memory pressure Message-ID: <CAPx1GvfftEFiqe6D19V1tUBx_MEuMKDyLjXhDiCVtrCXrrgedw@mail.gmail.com> In-Reply-To: <04794cad-eda5-4ab8-ae29-4cc4d53ac033@freebsd.org> References: <CAPx1GvfwqFqvMm0RkTvxa4BJStvOdG0=pNx2dCuWEzCXsqhqHw@mail.gmail.com> <slrnvnij2h.26bu.pmc@disp.intra.daemon.contact> <CAPx1GvfOh4g1AeOcYXC26W5jbPAgA_E_t7CW9chg4miC8c15-w@mail.gmail.com> <9e71d8eb-74c3-4bcb-89b1-90d4f9746168@quip.cz> <33db3282-25c4-42fb-8d97-1918d52fa9e2@denninger.net> <4094b79b-c54a-4953-b693-1b4e8387cf9f@freebsd.org> <slrnvnj05d.27gd.pmc@disp.intra.daemon.contact> <87928610-fcad-400e-b7b3-076c6d3f1200@freebsd.org> <12dcc55d-67ae-467b-9249-3d60047d05f0@denninger.net> <04794cad-eda5-4ab8-ae29-4cc4d53ac033@freebsd.org>
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On Sat, Jan 4, 2025 at 2:04=E2=80=AFPM Craig Leres <leres@freebsd.org> wrot=
e:
> Chris said he was "swapping to a zfs mirror" but I'm swapping to a gmirro=
r.
I thought I was, but now I'm not sure any more :-) (I set this up many
months ago). Poking around, it looks like I have a three way geom
mirror (why 3? I have no idea, well, some vague idea, but, well...).
I have `/dev/mirror/swap` as the swapon device in `/etc/fstab`, and
`gmirror list` says:
Geom name: swap
State: COMPLETE
Components: 3
Balance: load
Slice: 4096
Flags: NONE
GenID: 0
SyncID: 1
ID: 777312945
Type: AUTOMATIC
Providers:
1. Name: mirror/swap
Mediasize: 137438952960 (128G)
Sectorsize: 512
Stripesize: 4096
Stripeoffset: 0
Mode: r1w1e0
Consumers:
1. Name: ada2p3
Mediasize: 137438953472 (128G)
Sectorsize: 512
Stripesize: 4096
Stripeoffset: 0
Mode: r1w1e1
State: ACTIVE
Priority: 2
Flags: NONE
GenID: 0
SyncID: 1
ID: 466179938
[repeat for ada1p3 and ada0p3 but with priorities counting down to 0
and with different IDs.]
So I guess I'm swapping to a geom mirror. I suspect it has three
drives in it because I was originally thinking I had to swap to a zfs
vdev mirror.
You can stop here, but if not: MORE DETAILS
I originally put four drives in the machine (3 8TB + 1 old 2 TB), and
only three were working (ada0 through 2), so I set up a three-way zfs
file system on it. The fourth one worked on Linux but not on FreeBSD.
Eventually I moved it to a different channel and it started working
fine and I still don't know what that's all about, though there were
several kernel updates along the way (patch releases of FreeBSD 14) as
well.
At some point I discovered you can't crash-dump to a mirror, so I set
up a 64 GB partition on ada3 and made it the dump device. It might not
be working, I haven't forcibly tested it yet. Worse, `gpart show -l`
shows it as `swap2`, a duplicate of ada2's `swap2` except half the
size (??). It shows up fine as /dev/label/crash though.
`geom swap list -a` says:
Geom name: swap
Consumers:
1. Name: mirror/swap
Mediasize: 137438952960 (128G)
Sectorsize: 512
Stripesize: 4096
Stripeoffset: 0
Mode: r1w1e0
Strippng `geom -t` output a bit (egrep disk\|swap):
ada3p2 LABEL gpt/swap2
gpt/swap2 DEV
swap MIRROR mirror/swap
mirror/swap DEV
swap SWAP
swap MIRROR mirror/swap
mirror/swap DEV
swap SWAP
swap MIRROR mirror/swap
mirror/swap DEV
swap SWAP
swap.sync MIRROR
Here's `gpart show -p | grep swap`:
2048 134217728 ada3p2 freebsd-swap (64G)
534528 268435456 ada2p3 freebsd-swap (128G)
534528 268435456 ada1p3 freebsd-swap (128G)
534528 268435456 ada0p3 freebsd-swap (128G)
and `gpart show -l | grep swap`:
2048 134217728 2 swap2 (64G)
534528 268435456 3 swap2 (128G)
534528 268435456 3 swap1 (128G)
534528 268435456 3 swap0 (128G)
I went straight from an original FreeBSD 9 setup with an ancient MBR
(persisting unchanged through several upgrades) to FreeBSD 14 (now 15)
at home, so I get a bit lost between gpart, geom, and zfs/zpool
differences at times.
Chris
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