Is maximum swap usage tunable?

[bob prohaska]

In watching system compilations on an RPi3 it looks as if the
system starts killing processes with "out of swap" warnings 
well below 50% of full utilization (in this case, 2 GB). One
recent instance of make -j4 kernel-toolchain killed llvm-tblgen
with only 34% of the swap in use.

Is the maximum swap usage limit adjustable in any way? I didn't
recognize anything useful in the page at
https://www.freebsd.org/cgi/man.cgi?query=sysctl(8)&sektion=&manpath=freebsd-release-ports 

It's possible the problem is really swap speed, rather than size, so I'd
like to try changing size limits if possible. The swap media claims 2-3 
MB/sec random write speed and observations with gstat seem to support the
claim, but transient stalls are hard to observe. An RPi2 with similar 
hardware seems to have no problems.

Thanks for reading,

bob prohaska