From: "akr (Akira Tanaka)" <akr@...>
Date: 2013-08-24T09:23:25+09:00
Subject: [ruby-core:56792] [ruby-trunk - Feature #8809] Process.clock_getres


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


david_macmahon (David MacMahon) wrote:

>  I know it's not SI, but I often use ASCII "u" for Greek m ("��"), so :microsecond would be aliased by :us.

It may be possible.

I found ISO 2955.
ISO 2955: Information processing - Representation units in Systems with limited Character sets

>  > I feel :float_s is bit curious.
>  
>  How about separating the type and the resolution into two different parameters?
>  
>      Process.clock_getres(Process::CLOCK_MONOTONIC, :float, :second)
>  
>  ...or...
>  
>      Process.clock_getres(Process::CLOCK_MONOTONIC, Float, :second)

I think most useful combinations are follows.

* float second
* integer nanosecond (clock_gettime/clock_getres native format)

The current design makes us possible to specify
former as no unit argument and
later as :nanosecond.

Your design force us longer description for integer nanosecond.

----------------------------------------
Feature #8809: Process.clock_getres
https://bugs.ruby-lang.org/issues/8809#change-41334

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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