Introduction Into Java Profiling

Conference Talk for Coding Serbia conference.
Introduction into purpose of profiling and what mechanics are used to do it.
The second half of the talk were live demos of the referenced code examples and how to work with a profiler.

Transcript

1. Introduction Into Java Profiling
2. Two Reasons For Profiling
5. Quiz 1 ArrayList<String> arrayList = new ArrayList<>(); 2 arrayList.add("Coding Serbia");
6. Quiz /** * Appends the specified element to the end of this list. * * @param e element to be appended to this list * @return <tt>true</tt> (as specified by {@link Collection#add}) */ public boolean add(E e) { ensureCapacityInternal(size + 1); // Increments modCount!! elementData[size++] = e; return true; }
7. Attach Source
8. Profiling
9. We Can O Speed up code O Learn how code works O Have fun
10. Becoming a Cheeta O Execute less code O Waste less memory O Spend less time waiting
11. Code O Code execution consumes CPU cycles O Common issues O Frequent invocation O Long algorithm O Unnecessary code
12. Java is clever O javac optimizes sourcecode O HotSpot optimizes bytecode
13. javac private static final boolean PRINT = false; public static void main(String[] args) { if (PRINT) { System.out.println("Hello Serbia"); } }
14. HotSpot boolean print = false; public void doStuff() { for (int i = 0; i < 10_000_000; i++) { if (print) { System.out.println("Hello Serbia"); } } }
15. Memory O Java has automatic memory management O Common issues are O Garbage Collection O Memory Leaks
16. Garbage Collection O Limit Waste Long count = 0L; for (int i = 0; i < 10_000_000; i++) { count += i; }
17. Garbage Collection O Limit Waste Long count = 0L; for (int i = 0; i < 10_000_000; i++) { count = new Long(count.longValue()+ i); }
18. Memory Leaks O Forgotten reference keeps objects alive Map<Double, String> cache = new HashMap<>(); Double key = Math.random(); String value = "Coding Serbia"; cache.put(key, value); key = null;
19. Measuring
20. Time Wall Clock Elapsed Real CPU User + System
21. Unknown Code
22. Code t main() foo() bar() baz()
23. Sampling
24. t main() foo() bar() baz()
25. t main() foo() bar() baz()
26. t main() foo() bar()
28. Instrumentation
29. t main() foo() bar() baz()
30. t main() foo() bar() baz()
31. Sample First Instrument Later
32. Write your own Code Profiler https://github.com/CodingFabian/SamplingVsInstrumentation http://blog.codecentric.de/en/2011/10/measure-java- performance-sampling-or-instrumentation/
33. 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/
34. Profiling Demo
35. @CodingFabian https://github.com/CodingFabian https://speakerdeck.com/CodingFabian