Issue #8809 has been reported by akr (Akira Tanaka).

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Feature #8809: Process.clock_getres
https://bugs.ruby-lang.org/issues/8809

Author: akr (Akira Tanaka)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 


How about Process.clock_getres method?

POSIX defines clock_getres function to provide resolution information
of clocks.

I made a pacth to invoke clock_getres function.

  Process.clock_getres(Process::CLOCK_MONOTONIC) #=> 1.0e-09
  Process.clock_getres(Process::CLOCK_MONOTONIC_COARSE) #=> 0.00400025

The result means that the resolution of CLOCK_MONOTONIC is 1ns and
the resolution of CLOCK_MONOTONIC_COARSE is 4.00025ms.

Process.clock_getres has optional unit argument as Process.clock_gettime.

  Process.clock_getres(Process::CLOCK_MONOTONIC, :nanosecond) #=> 1
  Process.clock_getres(Process::CLOCK_MONOTONIC_COARSE, :nanosecond) #=> 4000250

It supports emulated clocks as well.

  Process.clock_getres(:SUS_GETTIMEOFDAY_BASED_CLOCK_REALTIME) #=> 1.0000000000000002e-06
  Process.clock_getres(:SUS_GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID) #=> 1.0000000000000002e-06

The unit argument can be :hertz, which means the reciprocal of the second.

  Process.clock_getres(:SUS_GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID, :hertz) #=> 1000000.0

Note that
Process.clock_getres(:POSIX_TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID, :hertz) is the clock ticks per second (CLK_TCK) and
Process.clock_getres(:ISO_C_CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID, :hertz) is CLOCK_PER_SEC.
I wanted to access them easily to investigate emulated clock behaviors on
various OSes.

Any comments?



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