From: Sylvain Joyeux <sylvain.joyeux@...>
Date: 2007-06-28T15:44:20+09:00
Subject: Re: when to Run the garbage collector?

On Thursday 28 June 2007, Bill Kelly wrote:
> From: "gz zz" <gpygood@126.com>
>
> > Thank you.
> > I only see rails use the 'GC.start' in my all 'gems'.e.g.
> > def test_time_recognition
> >    n = 10000
> >    if RunTimeTests
> >      GC.start
> >      rectime = Benchmark.realtime do
> >        n.times do
> >          rs.recognize_path("content")
> >          rs.recognize_path("content/list")
> >          rs.recognize_path("content/show/10")
> >          rs.recognize_path("admin/user")
> >          rs.recognize_path("admin/user/list")
> >          rs.recognize_path("admin/user/show/10")
> >        end
> >      end
> >      puts "\n\nRecognition (RouteSet):"
> >      per_url = rectime / (n * 6)
> >      puts "#{per_url * 1000} ms/url"
> >      puts "#{1 / per_url} url/s\n\n"
> >    end
> >  end
>
> It's doing GC.start there right before the Benchmark starts, just to
> help achieve a more consistent starting point, for measuring the
> elapsed time.
>
> Notice it only does the GC.start when benchmarks are being run.
It may be difficult to benchmark (or profile for that matter) code under 
GC: if the GC runs, you can get more than 200ms accounted to whichever 
method was being run.

If you can afford the memory allocation of your benchmarked code, try 
GC.start ; GC.disable before starting the bench.
-- 
Sylvain Joyeux