[Bug 257314] FBSD 13 crash after some KDE parts crash supposing out of swap space

From: <bugzilla-noreply_at_freebsd.org>
Date: Fri, 23 Jul 2021 19:04:59 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=257314

--- Comment #16 from Mark Millard <marklmi26-fbsd@yahoo.com> ---
(In reply to Mark Millard from comment #14)

The large I/O times may well be mostly wait-time in a queue
with a large queue built up of pending I/Os. So: the system
generating pages to write after than the I/O system is
writing them might be what is going on.

(An large accumulated set of pending reads may not be so
likely to be generated. That is why I picked on writing
out pages as an example.)

Again, I'm not sure the long I/O times are driving things.

I also made a silly assumption and there is another experiment:
increasing vm.pageout_oom_seq. I know someone used something
like:

vm.pageout_oom_seq=4000

I've no clue if there is a figure large enough to have numeric
overflows involved or other issues. But this figure likely can
be rather large.

The 120 value was enough to allow -j4 buildworld buildkernel to
complete on low end armv7 and aarch64 hardware. Mixed with
vm.pfault_oom_attempts=-1 it was enough for someone using a
microsd card as I remember. (My I/O context was better for
the purpose in such a context.)

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