From: "Sandor Szücs" <sandor.szuecs@...>
Date: 2009-02-26T05:56:11+09:00
Subject: Re: Help interpreting benchmark results


On 25.02.2009, at 13:20, Robert Klemme wrote:

> 2009/2/25 Sandor Szücs <sandor.szuecs@fu-berlin.de>:
>>
>> No. "real" measures the time that is passed from start to finish.
>>
>> Pseudocode
>>  real_start = Time.now
>>  yield # run test
>>  real_end = Time.now
>>  real_start.to_f - real_end.to_f
>>
>>
>> If the Kernel of your OS schedules another processes for, say 20  
>> seconds,
>> then the difference between total and real is >= 20 seconds.
>> I think the time called "real" should not be trusted in an  
>> evaluation.
>
> Not so fast.  If another process has been running that may well be a
> process spawned by our process.

Full ack that's right, if a process forks, like system() do you can  
measure
that one too.

Benchmark.bm(20) do |b|
   b.report 'fork' do
     pid = Process.fork { sleep 3 }
     Process.waitpid pid
   end
end
                           user     system      total        real
fork                  0.000000   0.010000   0.020000 (  3.008273)


regards, Sandor Szücs
--