[Python-Dev] PEP 564: Add new time functions with nanosecond resolution (original) (raw)
Victor Stinner victor.stinner at gmail.com
Tue Oct 17 18:05:24 EDT 2017
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Antoine Pitrou:
Why not
time.processtimens()?
I measured the minimum delta between two clock reads, ignoring zeros. I tested time.process_time(), os.times(), resource.getrusage(), and their nanosecond variants (with my WIP implementation of the PEP 564).
Linux:
- process_time_ns(): 1 ns
- process_time(): 2 ns
- resource.getrusage(): 1 us ru_usage structure uses timeval, so it makes sense
- clock(): 1 us CLOCKS_PER_SECOND = 1,000,000 => res = 1 us
- times_ns().elapsed, times().elapsed: 10 ms os.sysconf("SC_CLK_TCK") == HZ = 100 => res = 10 ms
- times_ns().user, times().user: 10 ms os.sysconf("SC_CLK_TCK") == HZ = 100 => res = 10 ms
Windows:
- process_time(), process_time_ns(): 15.6 ms
- os.times().user, os.times_ns().user: 15.6 ms
Note: I didn't test os.wait3() and os.wait4(), but they also use the ru_usage structure and so probably also have a resolution of 1 us.
It looks like currently, only time.process_time() has a resolution in nanoseconds (smaller than 1 us). I propose to only add time.process_time_ns(), as you proposed.
We might add nanosecond variant for the other functions once operating systems will add new functions with better resolution.
Victor
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