From: normalperson@...
Date: 2014-08-24T02:19:54+00:00
Subject: [ruby-core:64523] [ruby-trunk - Feature #10165] Use Process.clock_gettime to speed up Benchmark.realtime.

Issue #10165 has been updated by Eric Wong.


 Thanks Pete!  I committed your patch as r47260.
 I couldn't resist, so I also made r47622 to modify measure, too.
 (smaller improvement, 1.30s vs 1.44s on my VM)
 
 	require 'benchmark'
 	p(Benchmark.measure { 100000.times { Benchmark.measure {} } })

----------------------------------------
Feature #10165: Use Process.clock_gettime to speed up Benchmark.realtime.
https://bugs.ruby-lang.org/issues/10165#change-48461

* Author: Pete Higgins
* Status: Closed
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
----------------------------------------
This patch changes the Benchmark.realtime method to use the Process.clock_gettime internally when generating the time elapsed. Calling Process.clock_gettime is faster than the current way of creating Time objects.

I wrote a benchmark script (also attached) to demonstrate the difference:

```
require 'benchmark'

def old_benchmark
  r0 = Time.now
  yield
  Time.now - r0
end

def new_benchmark
  r0 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
  yield
  Process.clock_gettime(Process::CLOCK_MONOTONIC) - r0
end

n = (ARGV.first || 1_000_000).to_i

puts "#{n} iterations."

Benchmark.bmbm do |b|
  b.report("old") { n.times { old_benchmark { nil } } }
  b.report("new") { n.times { new_benchmark { nil } } }
end
```

When I run this on my local machine I see this output:

```
1000000 iterations.
Rehearsal ---------------------------------------
old   0.860000   0.000000   0.860000 (  0.863118)
new   0.360000   0.000000   0.360000 (  0.355242)
------------------------------ total: 1.220000sec

          user     system      total        real
old   0.870000   0.010000   0.880000 (  0.866577)
new   0.330000   0.000000   0.330000 (  0.328982)
```

I discussed this idea originally with Eric Hodel, but he has not reviewed this code.

---Files--------------------------------
benchmark_benchmark_realtime.rb (424 Bytes)
faster_benchmark_realtime.diff (909 Bytes)
faster_benchmark_realtime_2.diff (1.1 KB)


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