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Re: A third easy performance optimisation needed

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On 7/13/2017 2:19 PM, Joshua Cranmer 🐧 wrote:
> Before you do anything else, please start by using a proper Java 
> microbenchmarking harness (hint: if you're writing it yourself, it's not 
> a proper harness).
> 
> Rather, if you're trying to give a presentation on performance 
> optimizations, here's the rules you should be presenting instead:
> 
> 1. Ignore all advice on performance optimization that says "use X 
> instead of Y" or "avoid X." That's not to say it's all wrong, but much 
> of it is based on incorrect preconceptions or poorly-conducted studies. 
> At best, this sort of advice should generally be thought of as places to 
> start looking for performance improvements when you've identified problems.
> 
> 2. Learn how to measure performance properly (indeed, on any of this 
> kind of presentation, this should be the brunt of the presentation). In 
> particular, performance needs to be measured holistically, testing as 
> much of the system as possible. And evaluating performance improvements 
> needs to also avoid the pitfall of "we tuned the GC to not run on our 
> benchmark, fixing all performance issues!"
> 
> 2a. In particular, say no to microbenchmarks. They have their uses. But 
> their applicability is often minimal, far less than many people look for 
> in a benchmark. If you don't have the resources to be able to explain 
> why the optimizer is preferring differences (e.g., you're not reading 
> the assembly), then you likely don't have the ability to understand the 
> applicability, much less communicate the results properly.
> 
> 3. Performance optimization is a step that only happens once you've 
> measured and identified the bottlenecks. If you don't have the results 
> saying "this part right here is the problem," you're not ready yet.

Goetz has also written about microbenchmarks:

https://www.ibm.com/developerworks/java/library/j-jtp02225/

Arne

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A third easy performance optimisation needed Cecil Westerhof <Cecil@decebal.nl> - 2017-07-13 09:54 +0200
  Re:A third easy performance optimisation needed omegajunior <omegajunior@protonmail.com> - 2017-07-13 06:29 -0400
  Re: A third easy performance optimisation needed Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-13 11:27 +0000
  Re: A third easy performance optimisation needed Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-07-13 07:41 -0400
    Re: A third easy performance optimisation needed Eric Douglas <e.d.programmer@gmail.com> - 2017-07-13 05:48 -0700
      Re: A third easy performance optimisation needed Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 19:39 -0400
    Re: A third easy performance optimisation needed Cecil Westerhof <Cecil@decebal.nl> - 2017-07-13 15:14 +0200
      Re: A third easy performance optimisation needed Eric Douglas <e.d.programmer@gmail.com> - 2017-07-13 07:07 -0700
        Re: A third easy performance optimisation needed Robert Klemme <shortcutter@googlemail.com> - 2017-07-13 19:58 +0200
          Re: A third easy performance optimisation needed Cecil Westerhof <Cecil@decebal.nl> - 2017-07-13 20:02 +0200
  Re: A third easy performance optimisation needed Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 08:16 -0400
    Re: A third easy performance optimisation needed Eric Douglas <e.d.programmer@gmail.com> - 2017-07-13 06:08 -0700
      Re: A third easy performance optimisation needed Cecil Westerhof <Cecil@decebal.nl> - 2017-07-13 15:41 +0200
        Re: A third easy performance optimisation needed Eric Douglas <e.d.programmer@gmail.com> - 2017-07-13 07:09 -0700
          Re: A third easy performance optimisation needed Eric Douglas <e.d.programmer@gmail.com> - 2017-07-13 08:07 -0700
          Re: A third easy performance optimisation needed Cecil Westerhof <Cecil@decebal.nl> - 2017-07-13 18:37 +0200
        Re: A third easy performance optimisation needed Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2017-07-13 13:19 -0500
          Re: A third easy performance optimisation needed Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 14:32 -0400
      Re: A third easy performance optimisation needed Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 13:52 -0400
        Re: A third easy performance optimisation needed Eric Douglas <e.d.programmer@gmail.com> - 2017-07-14 07:52 -0700
  A third easy performance optimisation needed lewbloch@gmail.com - 2017-07-14 14:47 -0700

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