How to do fast performance timing

At Jane Street we have recently spend a lot of time trying to get a fast
gettimeofday. I saw lots of references in various postgres hacker threads
related to a lack of such a facility so ....

The culmination of those efforts can be read here:

https://github.com/janestreet/core/blob/master/lib/time_stamp_counter.mli
and

https://github.com/janestreet/core/blob/master/lib/time_stamp_counter.ml

it's all OCaml but the code is mostly imperative and very well documented.
In particular we made an effort to document our assumption. There are a
few which are ocaml specific. But a lot of the lessons we have learned
here should be applicable to postgres.

Hope this will be useful,

Cheers,

Bene

PS: We are releasing our code under the Apache license so you should feel
free to reuse the ideas.