Introduction Into Java Profiling

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Two Reasons For Profiling

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Quiz 1 ArrayList arrayList = new ArrayList<>(); 2 arrayList.add("Coding Serbia");

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Quiz /** * Appends the specified element to the end of this list. * * @param e element to be appended to this list * @return true (as specified by {@link Collection#add}) */ public boolean add(E e) { ensureCapacityInternal(size + 1); // Increments modCount!! elementData[size++] = e; return true; }

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Attach Source

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Profiling

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We Can O Speed up code O Learn how code works O Have fun

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Becoming a Cheeta O Execute less code O Waste less memory O Spend less time waiting

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Code O Code execution consumes CPU cycles O Common issues O Frequent invocation O Long algorithm O Unnecessary code

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Java is clever O javac optimizes sourcecode O HotSpot optimizes bytecode

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javac private static final boolean PRINT = false; public static void main(String[] args) { if (PRINT) { System.out.println("Hello Serbia"); } }

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HotSpot boolean print = false; public void doStuff() { for (int i = 0; i < 10_000_000; i++) { if (print) { System.out.println("Hello Serbia"); } } }

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Memory O Java has automatic memory management O Common issues are O Garbage Collection O Memory Leaks

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Garbage Collection O Limit Waste Long count = 0L; for (int i = 0; i < 10_000_000; i++) { count += i; }

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Garbage Collection O Limit Waste Long count = 0L; for (int i = 0; i < 10_000_000; i++) { count = new Long(count.longValue()+ i); }

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Memory Leaks O Forgotten reference keeps objects alive Map cache = new HashMap<>(); Double key = Math.random(); String value = "Coding Serbia"; cache.put(key, value); key = null;

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Measuring

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Time Wall Clock Elapsed Real CPU User + System

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Unknown Code

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Code t main() foo() bar() baz()

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Sampling

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t main() foo() bar() baz()

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t main() foo() bar() baz()

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t main() foo() bar()

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Instrumentation

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t main() foo() bar() baz()

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t main() foo() bar() baz()

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Sample First Instrument Later

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Write your own Code Profiler https://github.com/CodingFabian/SamplingVsInstrumentation http://blog.codecentric.de/en/2011/10/measure-java- performance-sampling-or-instrumentation/

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Write your own Memory Leak Hunter https://github.com/CodingFabian/JavaCollectionAnalyzer https://blog.codecentric.de/en/2012/01/find-java-memory-leaks- at-runtime-act-5/

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Profiling Demo

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@CodingFabian https://github.com/CodingFabian https://speakerdeck.com/CodingFabian