lib/benchmark.rb: speedup by reducing allocations

* lib/benchmark.rb (module Benchmark): define BENCHMARK_CLOCK
  (realtime): use Process.clock_gettime(BENCHMARK_CLOCK)
  [Feature #10165]

* test/benchmark/test_benchmark.rb (test_realtime_output): new test

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47260 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,11 @@
+Sun Aug 24 10:35:54 2014  Pete Higgins  <pete@peterhiggins.org>
+
+	* lib/benchmark.rb (module Benchmark): define BENCHMARK_CLOCK
+	  (realtime): use Process.clock_gettime(BENCHMARK_CLOCK)
+	  Reduces allocations to improve performance [Feature #10165]
+
+	* test/benchmark/test_benchmark.rb (test_realtime_output): new test
+
 Fri Aug 22 20:23:54 2014  Koichi Sasada  <ko1@atdot.net>
 
 	* string.c (rb_fstring): fix condition (easy to cause infinite loop!).

lib/benchmark.rb

@@ -286,13 +286,21 @@ module Benchmark
                        label)
   end
 
+  # :stopdoc:
+  if defined?(Process::CLOCK_MONOTONIC)
+    BENCHMARK_CLOCK = Process::CLOCK_MONOTONIC
+  else
+    BENCHMARK_CLOCK = Process::CLOCK_REALTIME
+  end
+  # :startdoc:
+
   #
   # Returns the elapsed real time used to execute the given block.
   #
   def realtime # :yield:
-    r0 = Time.now
+    r0 = Process.clock_gettime(BENCHMARK_CLOCK)
     yield
-    Time.now - r0
+    Process.clock_gettime(BENCHMARK_CLOCK) - r0
   end
 
   module_function :benchmark, :measure, :realtime, :bm, :bmbm

test/benchmark/test_benchmark.rb

@@ -152,4 +152,9 @@ BENCH
     t.add! { sleep 0.1 }
     assert_not_equal(0, t.real)
   end
+
+  def test_realtime_output
+    realtime = Benchmark.realtime { sleep 0.001 }
+    assert_in_delta 0.001, realtime
+  end
 end