Garbled console output on Pi3

[bob prohaska]

On Fri, Mar 09, 2018 at 01:44:30PM -0700, Ian Lepore wrote:
> On Wed, 2018-03-07 at 10:21 -0800, bob prohaska wrote:
> > From time to time I observe garbled console output on a Pi3 running -current.
> > The present revision is?
> > FreeBSD 12.0-CURRENT (ZEFOX) #1 r330571: Wed Mar??7 00:58:23 PST 2018
> > but I don't think that's special; the same thing has shown up sporadically
> > for the past month or so.
> > 
> > The output looks like this:
> > 
> > Mar??7 09:53:53 www kernel: pid 44970 (llvm-tblgen), uid 0, was killed: out of swap space
> > sswawpa_spp_apgaegr:er iw:ndsaewap fii_ppnand_ieptge fiweaanrig:eti??r:teb u wfiifannidt deefebr:i fnbuiiuffontife tberwajit:e??: bu0f, bufeblfokb nj:r:o:??0,w2 b b22u3fo94aibj,tl: k??b0nosui:,z fe b1siz87erlk6:n,??o:sbi 4zue: : 202f901o669b604,?
> > ????ej0sw: :
> > r:ag le4,0paap9 g6_epb
> > ???????inrkd: inendefifnioini:te t w1eai35t bu w2fai6t0f b,er:uf fbufoerbj: :bufo??bjs0:i , z0bl, blkeknno: 2: o16: 4260191,52
> > ?9393s7ize:,??1siz63e:84 4
> > 096
> > swap_pager: indefinite wait buffer: bufobj: 0, blkno: 210573, size: 4096
> > 
> > The first and last lines look normal, which seems to rule out errors in
> > the serial link.?
> 
> I can't come up with a reason for this.  This was normal in the old
> days, but console output is buffered these days, and the buffer size is
> 128 bytes on arm[64], so if things are going to interleave it should be
> in chunks of 128, not a few chars at a time like that.
> 
> Oh... unless it's a case of userland and the kernel writing to the
> terminal at the same time, independently of each other. ?Were you
> running the commands that are failing from the console?
> 
Nothing running from the console, all commands were through ssh sessions.

Can you suggest any experiments that might shed light on what's going on?
So far it seems -j8 buildworld and stress2 can provoke the effect.

Thanks for reading!

bob prohaska