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How Fast is Your Java Code
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How Fast is Your Java Code

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  • 1. How Fast is Your Java Code? Performance micro-benchmarking Dmitry Buzdin
  • 2. About Speaker buzdin@gmail.com @buzdinDmitry Buzdin
  • 3. Motivation
  • 4. Programming for Performance
  • 5. SituationSome developers optimize code a lotGood habits like:* Putting final keyword* Optimizing assignments* Creating less objects* Avoiding reflection
  • 6. SituationArguing who’s code is faster
  • 7. So how do youmeasure that?
  • 8. Macro-benchmarking vs Micro-benchmarking
  • 9. Challenge
  • 10. Challenge: How Fast is That?System.out.println("Hello, World!");
  • 11. DEMO
  • 12. 1 millisecond = 1 000 microseconds =1 000 000 nanoseconds
  • 13. Test NoiseClassloader activitiesReflection inflationGarbage collectionJIT compilation
  • 14. JIT CompilerBehavior-drivenCan compile and “de-compile”Client and Ser ver JITs are different
  • 15. Getting JVM StatsManagementFactory.getXYZBean()
  • 16. ClassLoadingMXBeanGarbageCollectorMXBeanRuntimeMXBeanMemoryMXBeanThreadMXBean...
  • 17. Measurement PitfallsMeasuring in millisecondsNot doing warm-upsNot doing enough warm-upsWrong JVM settingsToo few iterations
  • 18. Conclusions
  • 19. ConclusionsDo not do micro optimizationsWrite first - then measure criticalplacesProgram readability is more importantDo perform macro optimizationsinstead
  • 20. “We should forget about small efficiencies, say about 97% of thetime: premature optimization is the root of all evil” Donald Knuth
  • 21. Some Resources http://www.ibm.com/developer works/java/library/j-benchmark2/ index.htmlhttp://stackoverflow.com/questions/504103/how-do-i-write-a-correct- micro-benchmark-in-java http://docs.oracle.com/javase/specs/ jvms/se7 /html/index.html
  • 22. Code is on GitHubhttps://github.com/buzdin/java-microbenchmarking/
  • 23. The End