Re: RFC: import of posix_spawn GSoC results

[Martin Husemann <martin%duskware.de@localhost>]

I updated my patches after fixing a sever bug that caused fallout in lots
of (apparently unrelated) atf tests by fooling ld.elf_so into insecure
mode, thus not allowing LD_PRELOAD and breaking all the rump clients...

   ftp.netbsd.org:/pub/NetBSD/misc/martin/posix_spawn/newfiles_20120125.tar.gz
   
ftp.netbsd.org:/pub/NetBSD/misc/martin/posix_spawn/posix_spawn_20120125.diff.gz

I have been unable to find any statistically valid performance differences,
either between posix_spawn and vfork, nor between execv* on a patched vs.
an unpatched kernel - it is all in the sub-prommille range within a few
percent noise.

A working alternative aproach to this patch is to use a vfork based emulation
in userland only (FreeBSD is doing that). It is less kernel code, but to
me sounds a bit hackish and/or fragile - maybe a matter of personal taste.

I will ask core which of the two variants we want to go with.

Martin