ZDirector::one_in_1000 right-tailed vs two-tailed value

[Chris Thunes]

Apologies if this is the wrong place to direct this question.

I noticed that the ZDirector::one_in_1000 constant
(https://github.com/openjdk/zgc/blob/master/src/hotspot/share/gc/z/zDirector.cpp#L33)
seems to use a sigma value corresponding to a two-tailed test. Would
the right-tailed value (3.090232) make more sense in this case, given
that it is only high allocation rates and GC durations which would be
of concern for the allocation rate rule?

Best,
Chris Thunes