Unnest the Timer class

[alex]

classes are relatively expensive to create, and particularly disadvantageous on PyPy

A benchmark could be created if this was useful

[brian-brazil]

There's two other Timer classes.

How big is the performance difference?

[alex]

Using this simple benchmark:

from prometheus_client import Histogram


def main():
    h = Histogram("nonsense_latency_seconds", "Latency of nonsense (seconds)")

    for i in xrange(100000):
        with h.time():
            pass


if __name__ == "__main__":
    main()

On PyPy 5.1.1

WIth patch:

(tempenv-43511495362f0) ~ $ time python t.py
        0.22 real         0.17 user         0.04 sys
(tempenv-43511495362f0) ~ $ time python t.py
        0.23 real         0.18 user         0.04 sys
(tempenv-43511495362f0) ~ $ time python t.py
        0.23 real         0.18 user         0.05 sys

master:

(tempenv-43511495362f0) ~ $ time python t.py
        4.45 real         4.29 user         0.10 sys
(tempenv-43511495362f0) ~ $ time python t.py
        4.50 real         4.30 user         0.11 sys
(tempenv-43511495362f0) ~ $ time python t.py
        4.50 real         4.31 user         0.12 sys

So pretty massive. This optimization should be made to all the other nested Timer classes.

[brian-brazil]

That's a pretty nice improvement, most of the slowness is due to the mutex at that point.

[alex]

Indeed. Do you want me to move the other classes in this PR, or a separate one?

[brian-brazil]

All in one PR please.

[alex]

@brian-brazil done.

[brian-brazil]

We can remove this blank line now.

[brian-brazil]

That looks generally fine, can you squash your commits please?

[alex]

@brian-brazil done!

[brian-brazil]

Thanks!