Full swap partition

[George]

On Wed, 20 Feb 2019 16:46:33 +0000
Mike Clarke <jmc-freebsd2 at milibyte.co.uk> wrote:

> I'm running kde desktop on FreeBSD 11.2 on a system with 16GB RAM and
> 8GB swap. Normally I don't use any swap space but after a huge pkg
> upgrade three days ago I've suffered a problem with the entire swap
> partition filling up and the system freezing on about 4 occasions.
> 
> I suspect that this might be due to a bug in plasma5-plasma-workspace
> which was upgraded from version 5.14.5.1 to 5.15.0 because it now
> appears to require 128GB virtual memory
> 
> curlew:/home/mike% top -o size
> last pid:  1738;  load averages:  0.22,  0.32,  0.21     up
> 0+00:12:44  16:11:28 144 processes: 1 running, 142 sleeping, 1 zombie
> CPU 0:  0.8% user,  0.0% nice,  0.4% system,  0.4% interrupt, 98.4%
> idle CPU 1:  0.8% user,  0.0% nice,  0.4% system,  0.0% interrupt,
> 98.8% idle CPU 2:  1.6% user,  0.0% nice,  1.2% system,  0.0%
> interrupt, 97.3% idle CPU 3:  0.0% user,  0.0% nice,  0.0% system,
> 0.0% interrupt,  100% idle Mem: 1653M Active, 470M Inact, 2104M
> Wired, 40K Buf, 11G Free ARC: 1264M Total, 430M MFU, 801M MRU, 4703K
> Anon, 4920K Header, 24M Other 742M Compressed, 1059M Uncompressed,
> 1.43:1 Ratio Swap: 8192M Total, 8192M Free
> 
>   PID USERNAME     THR PRI NICE   SIZE    RES STATE   C   TIME
> WCPU COMMAND 1272 mike          13  20    0   128G   210M select  3
> 0:05   0.01% plasmashe
> 
> The corresponding value for SIZE before the upgrade was 293M.
> 
> The problem is only sporadic, I can run for several hours with no
> swap being used (as in the above output from top) and then it
> suddenly fills up.
> 

I had to set the kernel tune-able parameter for the max swap to use on
an NFS machine as it was experiencing out-of-swap space issues. I did a
search and found a post on the forums someone having a similar issue.
What I did was get the page number that was allocated by the installer
on setup and set in /boot/loader.conf it is called kern.maxswzone that
as far as I understand is a directive as to the max available if not
present the kernel books double ram which explains mine and and your
issue. Have been running like that is for a while now and no issues ...