There are a number of reports of userspace application crashes that
are "solved" by setting vm.pmap.pcid_enabled=0, including Java and the
x11/mate-terminal port (PR ports/184362).
I originally planned to disable this only in stable/10 (in r262753), but
it has been pointed out that additional crash reports on HEAD are not
likely to provide new insight into the problem. The feature can easily
be enabled for testing.