get_swap_pager(x) failed

[Mark Millard]

blubee blubeeme gurenchan at gmail.com wrote on
Tue Dec 12 15:58:19 UTC 2017 :

> On Tue, Dec 12, 2017 at 3:34 PM, blubee blubeeme <gurenchan at gmail.com
> >wrote:
> > I am seeing tons of these messages while running tail -f /var/log/messages
> > ============
> > Dec 12 15:11:41 blubee kernel: swap_pager_getswapspace(25): failed
> . . .
> >  1159 blubee        5  20    0   149M 56876K select  6   1:05   0.00%
> > ibus-engine-chewing
> >
> > ===========
> >
> > What's with all the swap errors? I am running ZFS and I have 16GB of ram,
> > how could I be having swap space errors?
> >
> 
> Well I added 4GB of extra swap in /var/tmp/swap0
> then added that to my /etc/fstab: md99                    none    swap
> sw,file=/var/tmp/swap0,late     0       0
> 
> and those errors went away.

I recommend reviewing bugzilla 206048 (title in part
"swapfile usage hangs; swap partition works"):

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=206048

before using file-system based swap spaces. They have
lots of problems with deadlocks. See especially comments
#7 and #8 quoting Konstantin Belousov. #8 is just a
reference to:

https://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug-deadlocks.html

Comment #3 shows a way to test for the problematical
behavior.

Using swap partitions avoids the issue.

===
Mark Millard
markmi at dsl-only.net