Importing mksh in base

[Bruce Evans]

On Fri, 25 Jan 2019, Rodney W. Grimes wrote:

>> I would like to import mksh in base, https://www.mirbsd.org/mksh.htm
>> And make it the default root shell (not necessary in one step)
>>
>> Why:
>> 1/ it is tiny 400k (in the packaged version) all other shells fitting the
>> expectation are bigger
> It is more than twice the size of our current /bin/sh, and giving up
> 200k on the nano/tiny/wifi BSD is hard to justify.  400k is near the
> size of tcsh.

That is only the dynamically linked size.  It is much larger and slower
than indicated by that.  Statically linked /bin/sh is now about 15 times
larger than in FreeBSD-1 (~1300K text instead of ~90K).  Dynamical linkage
costs more in runtime than the memory size expansion.  E.g., /bin/echo in
a shell loop is about 60% slower in -current than it was in FreeBSD-~5.2
using a CPU that is about twice as fast in -current and 8 CPUs instead of
1 (this should be good for CPU affinity of the shell process).  Dynamic
linkage alone is enough to give this slowdown.  Static linkages seems to
give a relatively smaller advantage in -current

Bruce