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Re: method micro benachmarking with reflection

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On 7/30/2015 5:33 PM, Volker Borchert wrote:
> Eric Sosman wrote:
>
>> Using JNI, you might be able to access chip-specific
>> low-level cycle counters or some such -- but even then, you'd have to
>> take it on faith that all the cycles between a method's start and end
>> were consumed by the method; what if the garbage collector decided to
>> preempt the method's thread for a few milliseconds?
>
> And what about the cost of going native? Or has that become a myth?

     I don't know what that cost is, nowadays.  However, if used
once at the start and once at the end of each instrumented method
it should add roughly the same overhead to each, inflating each
method's time by about the same amount.  I think it likely that
the other sources of interference already mentioned (JIT and re-JIT,
GC, preemption and migration of threads, ...) present greater hazards
to meaningful measurement.

     Besides: How do you imagine Java's own methods get the time?
 From the source supplied with the JDK:

	public final class System {
	    ...
	    public static native long currentTimeMillis();
	    ...
	    public static native long nanoTime();
	    ...
	}

Of course, the JVM might special-case "its own" native methods,
but still: A trip into the O/S seems difficult to avoid.

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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method micro benachmarking with reflection philipp.kraus.flashpixx@gmail.com - 2015-07-30 03:41 -0700
  Re: method micro benachmarking with reflection Arne Vajhøj <arne@vajhoej.dk> - 2015-07-30 07:16 -0400
    Re: method micro benachmarking with reflection Arne Vajhøj <arne@vajhoej.dk> - 2015-07-30 21:52 -0400
      Re: method micro benachmarking with reflection Arne Vajhøj <arne@vajhoej.dk> - 2015-07-30 21:55 -0400
  Re: method micro benachmarking with reflection Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-07-30 08:23 -0400
    Re: method micro benachmarking with reflection e.d.programmer@gmail.com - 2015-07-30 06:00 -0700
      Re: method micro benachmarking with reflection Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-07-30 09:30 -0400
        Re: method micro benachmarking with reflection e.d.programmer@gmail.com - 2015-07-30 08:26 -0700
          Re: method micro benachmarking with reflection Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-07-30 11:42 -0400
            Re: method micro benachmarking with reflection e.d.programmer@gmail.com - 2015-07-30 10:30 -0700
              Re: method micro benachmarking with reflection Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-07-30 14:20 -0400
        Re: method micro benachmarking with reflection Jeff Higgins <jeff@invalid.invalid> - 2015-07-30 16:08 -0400
    Re: method micro benachmarking with reflection philipp.kraus.flashpixx@gmail.com - 2015-07-30 06:11 -0700
    Re: method micro benachmarking with reflection v_borchert@despammed.com (Volker Borchert) - 2015-07-30 21:33 +0000
      Re: method micro benachmarking with reflection Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-07-30 18:18 -0400
        Re: method micro benachmarking with reflection Arne Vajhøj <arne@vajhoej.dk> - 2015-07-30 20:13 -0400
  Re: method micro benachmarking with reflection Jeff Higgins <jeff@invalid.invalid> - 2015-07-30 17:11 -0400
  Re: method micro benachmarking with reflection v_borchert@despammed.com (Volker Borchert) - 2015-07-30 21:53 +0000
  Re: method micro benachmarking with reflection Sebastian <news@seyweiler.dyndns.org> - 2015-08-04 21:44 +0200

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