On Sun, 11 Mar 2018, Mark Millard wrote:

As I understand, O. Hartmann's report ( ohartmann at walstatt.org ) in:


includes a system with a completely non-ZFS context: UFS only. Quoting that 

This is from a APU, no ZFS, UFS on a small mSATA device, the APU (PCenigine) 
works as a
firewall, router, PBX):

last pid:  9665;  load averages:  0.13,  0.13,  0.11
up 3+06:53:55  00:26:26 19 processes:  1 running, 18 sleeping CPU:  0.3% user,  
nice,  0.2% system,  0.0% interrupt, 99.5% idle Mem: 27M Active, 6200K Inact, 
Laundry, 185M Wired, 128K Buf, 675M Free Swap: 7808M Total, 2856K Used, 7805M 

The APU is running CURRENT ( FreeBSD 12.0-CURRENT #42 r330608: Wed Mar  7 
16:55:59 CET
2018 amd64). Usually, the APU never(!) uses swap, now it is starting to swap 
like hell
for a couple of days and I have to reboot it failty often.

Unless this is unrelated, it would suggest that ZFS and its ARC need not
be involved.

Would what you are investigating relative to your "NUMA and concurrency
related work" fit with such a non-ZFS (no-ARC) context?

I think there are probably two different bugs. I believe the pid controller has caused the laundry thread to start being more aggressive causing more pageouts which would cause increased swap consumption.

The back-pressure mechanisms in arch should've resolved the other reports. It's possible that I broke those. Although if the reports from 11.x are to be believed I don't know that it was me. It is possible they have been broken at different times for different reasons. So I will continue to look.


Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)

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