"Эффективность и оптимизация кода в Java 8" Сергей Моренец
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Если мы захотим понять, что такое совершенный(идеальный) код, то одной из его характеристик будет эффективность. Это включает в себя и быстродействие кода, и объем потребляемых ресурсов(память, дисковых, I/O). Зачастую эффективность отодвигается на второй план, поскольку ее не так просто рассчитать заранее, а также точно определить на ревью кода. В то же время это единственная характеристика, которая затрагивает конечного пользователя наших проектов. В моем докладе я рассмотрю, что такое эффективность, как ее правильно измерять, мы коснемся мифов об эффективности, которые очень популярны сейчас, рассмотрим примеры эффективного и неэффективного кода, нужной и бессмысленной оптимизации кода. Главный упор будет сделан на функциональности, которая была добавлена в Java 8.
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"Эффективность и оптимизация кода в Java 8" Сергей Моренец
- 1. Заголовок презентации Имя и фамилия автора доклада Компания Контактные данные 1 Контактные данные 2 Контактные данные 3 Контактные данные 4 Effectiveness and code optimization in Java applications Sergey Morenets [email protected]
- 2. About author • Works in IT since 2000 • 12 year of Java SE/EE experience • Regular speaker at Java conferences • Author of “Development of Java applications” and “Main errors in Java programming ”books • Founder of http://it-simulator.com
- 3. Preface
- 4. Agenda
- 5. Agenda • What is effectiveness? • Code optimization • JVM optimization • Code samples • Measurements
- 6. Ideal code Concise Readable Self-describing Reusable Testable Modern Flexible Scalable Effective
- 7. Effectiveness • Hard to determine on code/design review stages or in unit-tests • Is relevant for the specific project configuration/environment • Premature optimization is evil • Hardware-specific • The only aspect of the code that affects users
- 16. Effectiveness • Can be measured • Can be static or dynamic • Can be tuned
- 17. Tuning • JVM options • Metaspace/heap/stack size • Garbage collector options • http://blog.sokolenko.me/2014/11/javavm- options-production.html • http://www.javaspecialists.eu/
- 18. Code optimization Java compiler JIT compiler JVM
- 20. Code optimization public int execute(); Code: 0: iconst_2 1: istore_1 2: iinc 1, 1 5: iconst_1 6: ireturn
- 22. Code optimization public int execute(); Code: 0: iconst_2 1: istore_1 2: iconst_1 3: ireturn
- 24. Code optimization public void execute(); Code: 0: return
- 26. Code optimization public static boolean get(); Code: 0: iconst_1 1: ireturn
- 28. Code optimization public void execute(); Code: 0: return
- 30. Code optimization public int execute(); Code: 0: iconst_2 1: istore_1 2: iconst_4 3: istore_2 4: iload_1 5: iload_2 6: iadd 7: ireturn
- 32. Code optimization public int execute(); Code: 0: bipush 6 2: ireturn
- 34. Code optimization public int execute(); Code: 0: bipush 12 2: ireturn
- 35. Javacompiler Dead code elimination Constant folding Fixed expression calculation
- 36. Measurements • JMH is micro benchmarking framework • Developed by Oracle engineers in 2013 • Requires build tool(Maven, Gradle) • Can measure throughput or average time • Includes warm-up period
- 37. Warm-up
- 38. Environment • JMH 1.11.3 • Maven 3.3.9 • JDK 1.8.0.73 • Intel Core i7 4790, 4 cores, 16 GB
- 39. Measurements Type Time(ns) Multiply 4 2,025 Shift 2,024
- 40. Measurements Type Time(ns) Multiply 17 2,04 Shift 2,04
- 42. Method vs Field
- 44. Inversion
- 45. Inversion
- 46. Measurements Type Time(ns) ! 1,99 ? 1,99 ^ 2,01
- 47. Arrays
- 48. Measurements Type Time(ns) For (10 elements) 4,9 For-each (10 elements) 5,1 For (1000 elements) 260 For-each (1000 elements) 259,9 For (50000 elements) 12957 For-each (50000 elements) 12958
- 49. Arrays
- 50. Measurements Type Time(ns) For (10 elements) 5,04 For optimized(10 elements) 5,07 For (1000 elements) 258,9 For-each (1000 elements) 258,7
- 51. Arrays
- 52. Measurements Type Time(ns) Sequential (10 elements) 5 Parallel (10 elements) 6230 Sequential (1000 elements) 263 Parallel (1000 elements) 8688 Sequential (50000 elements) 13115 Parallel (50000 elements) 34695
- 53. Measurements Type Time(ns) Sequential (10 elements) 5 Parallel (10 elements) 6230 Sequential (1000 elements) 263 Parallel (1000 elements) 8688 Sequential (50000 elements) 13115 Parallel (50000 elements) 34695 Sequential (5 000 000 elements) 1 765 206 Parallel (5 000 000 elements) 2 668 564 Sequential (500 000 000) 183 ms Parallel (500 000 000) 174 ms
- 54. Autoboxing
- 55. Measurements Type Time(ns) Array(100 elements) 58 List(100 elements) 390 Array(10 000 elements) 4776 List(10 000 elements) 48449
- 56. LIFO
- 58. Stack
- 59. Java NIO
- 60. Measurements 100 elements Array Heap buffer Direct buffer Create 13,87 18,9 502,5 Get 2,24 3,18 2,65 Update 2,26 3,21 2,93 Update all 29,5 33,2 36,6
- 61. Measurements 10000 elements Array Heap buffer Direct buffer Create 544 548 1543 Get 2,25 3,26 2,77 Update 2,38 3,19 2,94 Update all 2701 2720 5022
- 62. Collections
- 63. Collections Type Time(ns) Fill HashMap(1000 elements) 16000 Fill TreeMap(1000 elements) 40115 Fill HashMap(100 000 elements) 2 027 116 Fill TreeMap(100 000 elements) 11 195 422 Iteration HashMap(1000 elements) 3086 Iteration TreeMap(1000 elements) 5038
- 64. Reflection
- 65. Measurements Type Time(ns) New object 3,0 Reflection 5,4
- 66. Reflection
- 67. Measurements Type Time(ns) Method call 0,3 Reflection 232
- 68. Measurements Type Time(ns) Method call 0,3 Reflection (cached) 3,1
- 70. Lists
- 71. Measurements Type Time(ns) ArrayList (1000 elements) 4766 ArrayList (100 000 elements) 381707 LinkedList (1000 elements) 5504 LinkedList (100 000 elements) 504231
- 72. Lists
- 73. Measurements Type Time(ns) ArrayList (1000 elements) 26767 ArrayList (100 000 elements) 276(ms) LinkedList (1000 elements) 300971 LinkedList (100 000 elements) 3424(ms)
- 74. Lists
- 75. Measurements Type Time(ns) ArrayList (1000 elements) 774 ArrayList (100 000 elements) 144814 LinkedList (1000 elements) 2161 LinkedList (100 000 elements) 292364
- 78. Measurements Type (elements) Time(ns) ArrayList (1000) 4732 ArrayList (100 000) 387692 LinkedList (1000) 5775 LinkedList (100 000) 511646 ObjectArrayList(1000) 3168 ObjectArrayList(100 000) 322811
- 80. Measurements Type(1 thread) Time(ns) Not synchronized 2,0 Synchronized method 18,3 Synchronized block 18,3
- 84. Measurements Type (1 thread) Time(ns) ReentrantLock 18,7 ReadWriteLock 19,0 StampedLock 18,6
- 85. Synchronization
- 86. Measurements Type (16 threads) Time(ns) ReentrantLock 54,2 ReadWriteLock 56,4 StampedLock 52,5 AtomicLong 8,8
- 87. Java 7
- 88. Java 8
- 89. Java 8
- 90. Measurements Type Time(ns) Anonymous class 2,03 Lambda expression 2,37 Method reference 2,38
- 91. Java 7
- 92. Java 8
- 93. Measurements Type(# elements) Time(ns) For-loop(10) 5,0 Stream(10) 35,2 For-loop(1000) 264 Stream(1000) 1970 For-loop(50 000) 13244 Stream(50 000) 95689
- 94. Parallel streams
- 95. Measurements Type(# elements) Time(ns) Sum sequential(100) 6 Sum parallel(100) 51 Sleep sequential(100) 101 106 306 Sleep parallel(100) 13 575 733 Sum sequential(10000) 19517 Sum parallel(10000) 15657 Sleep sequential(10000) 10 068 771 891 Sleep parallel(10000) 1 250 911 296
- 96. Default methods
- 98. JIT optimization • Inline methods • Eliminate locks • Replace interface with direct method calls • Join synchronized blocks • Eliminate dead code • Drop memory write for non-volatile variables
- 99. Conclusion • Compiler and JIT optimization • Speed and memory optimization • Prefer ArrayList/HashMap • Synchronization and reflection cost • Use measurement tools
- 100. Theory