k0kubun	2017-05-28 10:48:11 +0900 (Sun, 28 May 2017)

  New Revision: 58935

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=58935

  Log:
    process.c: Use getrusage(2) in Process.times
    
    if getrusage(2) is available, to improve precision of Process.times and
    its user like lib/benchmark.rb.
    
    On macOS, since getrusage(2) has better precision than times(3),
    they are much improved like:
    
    * Before
    
    Process.times
    => #<struct Process::Tms utime=0.56, stime=0.35, cutime=0.04, cstime=0.03>
    
    puts Benchmark.measure { "a" * 1_000_000_000 }
      0.340000   0.310000   0.650000 (  0.674025)
    
    * After
    
    Process.times
    => #<struct Process::Tms utime=0.561899, stime=0.35076, cutime=0.046483, cstime=0.038929>
    
    puts Benchmark.measure { "a" * 1_000_000_000 }
      0.343223   0.310037   0.653260 (  0.674025)
    
    On Linux, since struct rusage from getrusage(2) is used instead of struct tms
    from times(2), they are slightly improved like:
    
    * Before
    
    Process.times
    => #<struct Process::Tms utime=0.43, stime=0.11, cutime=0.0, cstime=0.0>
    
    puts Benchmark.measure { "a" * 1_000_000_000 }
      0.120000   0.040000   0.170000 (  0.171621)
    
    * After
    
    Process.times
    => #<struct Process::Tms utime=0.432, stime=0.116, cutime=0.0, cstime=0.0>
    
    puts Benchmark.measure { "a" * 1_000_000_000 }
      0.124000   0.048000   0.172000 (  0.171621)
    
    [ruby-dev:49471] [Feature #11952]

  Modified files:
    trunk/NEWS
    trunk/process.c
Index: process.c
===================================================================
--- process.c	(revision 58934)
+++ process.c	(revision 58935)
@@ -6887,15 +6887,26 @@ get_clk_tck(void) https://github.com/ruby/ruby/blob/trunk/process.c#L6887
 VALUE
 rb_proc_times(VALUE obj)
 {
+    VALUE utime, stime, cutime, cstime, ret;
+#if defined(RUSAGE_SELF) && defined(RUSAGE_CHILDREN)
+    struct rusage usage_s, usage_c;
+
+    if (getrusage(RUSAGE_SELF, &usage_s) != 0 || getrusage(RUSAGE_CHILDREN, &usage_c) != 0)
+	rb_sys_fail("getrusage");
+    utime = DBL2NUM((double)usage_s.ru_utime.tv_sec + (double)usage_s.ru_utime.tv_usec/1e6);
+    stime = DBL2NUM((double)usage_s.ru_stime.tv_sec + (double)usage_s.ru_stime.tv_usec/1e6);
+    cutime = DBL2NUM((double)usage_c.ru_utime.tv_sec + (double)usage_c.ru_utime.tv_usec/1e6);
+    cstime = DBL2NUM((double)usage_c.ru_stime.tv_sec + (double)usage_c.ru_stime.tv_usec/1e6);
+#else
     const double hertz = get_clk_tck();
     struct tms buf;
-    VALUE utime, stime, cutime, cstime, ret;
 
     times(&buf);
     utime = DBL2NUM(buf.tms_utime / hertz);
     stime = DBL2NUM(buf.tms_stime / hertz);
     cutime = DBL2NUM(buf.tms_cutime / hertz);
     cstime = DBL2NUM(buf.tms_cstime / hertz);
+#endif
     ret = rb_struct_new(rb_cProcessTms, utime, stime, cutime, cstime);
     RB_GC_GUARD(utime);
     RB_GC_GUARD(stime);
Index: NEWS
===================================================================
--- NEWS	(revision 58934)
+++ NEWS	(revision 58935)
@@ -59,6 +59,10 @@ with all sufficient information, see the https://github.com/ruby/ruby/blob/trunk/NEWS#L59
     of #coerce. Return nil in #coerce if the coercion is impossible.
     [Feature #7688]
 
+* Process
+
+  * Precision of Process.times is improved if getrusage(2) exists. [Feature #11952]
+
 * Range
   * Range#initialize no longer rescue exceptions when comparing begin and
     end with #<=> and raise a "bad value for range" ArgumentError

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