As it was pointed out by Alan Cox, that no longer serves its purpose with
the modern UMA allocator compared to the old one used in 4.x days.
The removal of sysctl eliminates max_proc_mmap type overflow leading to
the broken mmap(2) seen with large amount of physical memory on arches
with factually unbound KVA space (such as amd64). It was found that
slightly less than 256GB of physmem was enough to trigger the overflow.
Reviewed by: alc, kib
Approved by: avg (mentor)
MFC after: 2 months
