Principios básicos de Garbage Collector en Java
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The document discusses Java garbage collection (GC), focusing on issues that can lead to application crashes, such as improper data type selection and memory leaks. It outlines various GC algorithms including mark-and-sweep, generational GC, and presents demonstrations of problematic code patterns. The author emphasizes best practices in programming to mitigate GC-related issues, highlighting the importance of algorithm complexity and efficient memory management.
![Demo 3 - Concatenaci´on de String
//...
static String texto = "";
public static void main(String [] args ){
var numeros = IntStream.iterate (1, t -> ++t);
numeros.forEach(n -> {
texto += " " + n;
if(n % 10 _000 == 0) System.out.println(n);
});
}
//...
27](https://image.slidesharecdn.com/main-180511021248/85/Principios-basicos-de-Garbage-Collector-en-Java-31-320.jpg)
![Demo 4 - StringBuffer
//...
static StringBuilder texto = new StringBuilder("");
public static void main(String [] args ){
var numeros = IntStream.iterate (1, t -> ++t);
numeros.forEach(n -> {
texto.append(" ");
texto.append(n);
if(n % 10 _000 == 0) System.out.println(n);
});
}
//...
28](https://image.slidesharecdn.com/main-180511021248/85/Principios-basicos-de-Garbage-Collector-en-Java-32-320.jpg)
Principios básicos de Garbage Collector en Java
- 1. Introducci´on al GC en Java - Porqu´e mis aplicaciones explotan V´ıctor Orozco - @tuxtor 10 de mayo de 2018 GuateJUG 1
- 2. V´ıctor Orozco • Developer (JVM/Open Source Advocate) • JUG Leader • Consultor independiente • Profesor universitario • @tuxtor • http://vorozco.com • http://tuxtor.shekalug.org 2
- 3. TLDR Explosi´on • Mala selecci´on de tipos de dato • Muchas variables y referencias (memory leak) • Algoritmos innecesariamente complejos • Muchas apps y poca memoria 3
- 5. Stack vs heap Figura 1: Stack y Heap 4
- 6. Stack vs heap Figura 2: Java main thread 5
- 7. Mark and sweep Figura 3: Mark and sweep, Credits: https://plumbr.io 6
- 8. Mark and sweep Figura 4: Mark and sweep - Mark, Credits: https://plumbr.io Generalmente DFS 7
- 9. Mark and sweep Figura 5: Mark and sweep - sweep, Credits: https://plumbr.io 8
- 10. Mark and sweep Figura 6: Mark - sweep, Credits: https://plumbr.io 9
- 11. Mark - sweep - compact Figura 7: Mark - sweep - compact, Credits: https://plumbr.io 10
- 12. Mark and copy Figura 8: Mark and copy, Credits: https://plumbr.io 11
- 13. Demo 0 - Generaci´on de objetos //... Stream <Integer > nums = Stream.iterate (1, n -> n + 1); nums.forEach(num -> { System.out.println(num); try{Thread.sleep (10);} catch( InterruptedException ex){} } ); //... 12
- 15. Generational GC(HotSpot) Figura 9: Generational GC, Credits: Oracle 13
- 16. Generational GC(HotSpot) Figura 10: Generational GC, Credits: Oracle 14
- 17. Generational GC(HotSpot) Figura 11: Generational GC, Credits: Oracle 15
- 18. Generational GC(HotSpot) Figura 12: Generational GC, Credits: Oracle 16
- 19. Generational GC(HotSpot) Figura 13: Generational GC, Credits: Oracle 17
- 20. Generational GC(HotSpot) Figura 14: Generational GC, Credits: Oracle 18
- 21. Generational GC(HotSpot) Figura 15: Generational GC, Credits: Oracle 19
- 22. Demo 1 - GC Generacional //... Stream <Integer > nums = Stream.iterate (1, n -> n + 1); var numeros = new ArrayList <Integer >(); nums.forEach(num -> { System.out.println(num); numeros.add(num); }); //... java -XX:+UseSerialGC DemoMemoriaGenerations 20
- 23. GC en HotSpot
- 24. Recolectores de basura • Serial GC para Young y Old generations • Parallel GC para Young y Old generations • Parallel New para Young + Concurrent Mark and Sweep (CMS) para Old Generation • G1GC, para Young y Old generations 21
- 25. SerialGC • Young: Mark-Copy • Old: Mark-Sweep-Compact • java − XX : +UseSerialGCcom.nabenik.MyExecClass 22
- 26. ParallelGC • Young: Mark-Copy • Old: Mark-Sweep-Compact • Stop-the-world en ambas regiones • java − XX : +UseParallelGCcom.nabenik.MyExecClass 23
- 27. CMS • Young: Mark-Copy - Stop the world • Old: (Mostly )Concurrent Mark Sweep (Paralelo) • java − XX : +UseConcMarkSweepGCcom.nabenik.MyExecClass 24
- 28. Como luchar CONTRA un Garbage Collector
- 29. Demo 1 - Referencias + Mal tipo de dato //... var lasReferencias = new ArrayList <String >(); Stream <Integer > numeros = Stream.iterate (1, n -> ++n); numeros.forEach(n -> { lasReferencias.add(n + ""); if( lasReferencias.size () % 10 _000_000 == 0){ System.out.println(n); try{ Thread.sleep (3000); } catch( InterruptedException e){} } }); } //... 25
- 30. Demo 2 - Referencias //... var lasReferencias = new ArrayList <Integer >(); var numeros = IntStream.iterate (1, n -> ++n); numeros.forEach(n -> { lasReferencias.add(n); if( lasReferencias.size () % 10 _000_000 == 0){ System.out.println(n); try{ Thread.sleep (3000); } catch( InterruptedException e){} } }); //... 26
- 31. Demo 3 - Concatenaci´on de String //... static String texto = ""; public static void main(String [] args ){ var numeros = IntStream.iterate (1, t -> ++t); numeros.forEach(n -> { texto += " " + n; if(n % 10 _000 == 0) System.out.println(n); }); } //... 27
- 32. Demo 4 - StringBuffer //... static StringBuilder texto = new StringBuilder(""); public static void main(String [] args ){ var numeros = IntStream.iterate (1, t -> ++t); numeros.forEach(n -> { texto.append(" "); texto.append(n); if(n % 10 _000 == 0) System.out.println(n); }); } //... 28
- 34. Complejidad Complejidad = Cantidad de pasos para realizar una tarea Figura 16: Complejidad computacional Tambi´en conocido como ”programar bien”:O 29
- 35. Fibonacci Figura 17: Sucesi´on Fibonacci 30
- 36. Demo 5 - Mal Fibonacci //... public static long doFibonacci(int n) { if (n <= 1) return n; else return doFibonacci(n-1) + doFibonacci(n -2); } //... 31
- 37. Demo 6 - Buen Fibonacci //... public static long doFibonacci(int n) { long a=0, b=1, c=0; for(int i = 0 ; i < n; i++){ c = a + b; a = b; b = c; } return c; } //... 32
- 38. Gracias • me@vorozco.com • http://vorozco.com • http://github.com/tuxtor/slides This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Guatemala License. 33