https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=230454

Mark Millard <marklmi26-f...@yahoo.com> changed:

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--- Comment #6 from Mark Millard <marklmi26-f...@yahoo.com> ---
(In reply to Warner Losh from comment #5)

While Bob P.'s reports were with large gstat reporting large
ms/w and/or ms/r, Trev had made reports of getting the problem
without gstat indicating multi-second delays (averages for some
time intervals) and having lots of swap still available, starting
at:

https://lists.freebsd.org/pipermail/freebsd-arm/2018-June/018151.html

(But Trev only provided short segments of the records in
messages instead of posting the whole logs somewhere. This
limits confirmation.)



Note to avoid misinterpretation: I am in general agreement with
the following as appropriate experiments . . .

"You need to add non-flash swap"
and
"Spinning disks suffer much less from these issues"

although I would explicitly add that there are SSD-based USB
drives and at least some of these might be about as good as
using a direct SATA SSD environment with good SSDs. (Correct
me if I'm wrong for some reason.)

Notes on testing:

Having records from, say, periodic gstat runs, is a good cross
check in all cases. Having the information-reporting patches
from Mark Johnston are appropriate for testing as well.

http://www.zefox.net/~fbsd/rpi3/swaptests/tools/ has various
things that have been used in testing. But batchqueue.patch
did not pan out and likely should be avoided. Similarly for
config_options. The readme is what talks about:

sysctl vm.pageout_oom_seq=120

The rest are patches for reporting of additional information
during operation. These are likely more important than the
gstat ms/w and ms/r records.

The context for the patches is recent head, not 11.x .

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