-- What is effectiveness? -- Code optimization -- JVM optimization -- Code samples -- Measurements

1. Effectiveness and code optimization
in Java
Sergey Morenets, sergey.morenets@gmail.com
December, 4 2015

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
• Cannot be defined in development environment
• Depends on the application environment
• Premature optimization is evil
• Hardware-specific
• The only aspect of the ideal code that affects users

8. Premature optimization

9. Premature optimization

10. Premature optimization

11. Premature optimization

12. Premature optimization

13. Effectiveness
CPU
utilization
Memory
utilization
Network I/O
utilization
Disk I/O
utilization

14. Effectiveness
• Can be measured
• Can be static or dynamic
• Can be tuned

15. Tuning
• JVM options
• Metaspace/heap/stack size
• Garbage collector options
• http://blog.sokolenko.me/2014/11/javavm-options-
production.html
• http://www.javaspecialists.eu/

16. Code optimization
Java compiler
JIT compiler
JVM

17. Code optimization

18. Code optimization
public int execute();
Code:
0: iconst_2
1: istore_1
2: iinc 1, 1
5: iconst_1
6: ireturn

19. Code optimization

20. Code optimization
public int execute();
Code:
0: iconst_2
1: istore_1
2: iconst_1
3: ireturn

21. Code optimization

22. Code optimization
public void execute();
Code:
0: return

23. Code optimization

24. Code optimization
public static boolean get();
Code:
0: iconst_1
1: ireturn

25. Code optimization

26. Code optimization
public void execute();
Code:
0: return

27. Code optimization

28. 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

29. Code optimization

30. Code optimization
public int execute();
Code:
0: bipush 6
2: ireturn

31. Code optimization

32. Code optimization
public int execute();
Code:
0: bipush 12
2: ireturn

33. Javacompiler
Dead code elimination
Constant folding
Fixed expression calculation

34. Measurements
• JMH is micro benchmarking framework
• Developed by Oracle engineers
• First release in 2013
• Requires build tool(Maven, Gradle)
• Can measure throughput or average time
• Includes warm-up period

35. Warm-up

36. Environment
• JMH 1.11.1
• Maven 3.3.3
• JDK 1.8.0.65
• Intel Core i7, 4 cores, 16 GB

37. Measurements
Type Time(ns)
Multiply 4 2,025
Shift 2,024

38. Measurements
Type Time(ns)
Multiply 17 2,04
Shift 2,04

39. Sample

40. Method vs Field

41. Measurements
Type Time(ns)
Field 1,945
Method 1,933

43. Measurements
Type Time(ns)
Static 2,17
Instance 2,30

44. Increment

45. Measurements
Type Time(ns)
Addiction 2,06
Incrementation 2,06

46. Swap

47. Measurements
Type Time(ns)
Standard 2,10
Addiction 2,08
XOR 2,04

48. Conditions

49. Measurements
Type Time(ns)
Ternary operation 2,05
If operator 2,03

50. Parsing

51. Measurements
Type Time(ns)
Long usage(small numbers) 3
Long usage(average numbers) 19
Long usage(big numbers) 33
Long usage (not a number) 849
Regexp (small numbers) 58
Regexp (average numbers) 75
Regexp (big numbers) 82
Regexp (not a number) 47

52. Copying arrays

53. Measurements
Type Time(ns)
Loop(1000 elements) 52,6
arrayCopy(1000 elements) 45,6
Loop(100 000 elements) 21666
arrayCopy(100 000 elements) 21707
Loop(10 000 000 elements) 6432557
arrayCopy(10 000 000 elements) 6616976

55. Measurements
Type Time(ns)
Rows(10 elements) 37
Columns(10 elements) 67
Rows(100 elements) 2954
Columns(100 elements) 5567
Rows(1000 elements) 264340
Columns(1000 elements) 1300244
Rows(5000 elements) 9,6(ms)
Columns(5000 elements) 387(ms)

56. Strings

57. Measurements
Type Time(ns)
+ 7,62
Concat 13,4
StringBuffer 7,32
StringBuilder 7,24

58. Maps

59. Measurements
Type Time(ns)
Entries (10 pairs) 30
Keys/Values(10 pairs) 70
Entries (1000 pairs) 2793
Keys/Values(1000 pairs) 8798
Entries (200 000 pairs) 237652
Keys/Values(200 000 pairs) 350821

60. Arrays

61. 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

62. Arrays

63. 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

64. Arrays

65. 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

66. 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

67. Exceptions

68. Measurements
Type Time(ns)
If 2,40
Exceptions 2,47

69. Strings

70. Strings

71. Measurements
Type Time(ns)
Parse(1000 tokens) 12239
Parse with intern(1000 tokens) 72814

72. Arrays

73. Bitset

74. Measurements
Type Time(ns)
Fill array (1000 elements) 148
Fill bit set(1000 elements) 1520
Fill array (50 000 elements) 4669
Fill bit set(50 000 elements) 71395

75. Bitset

76. Measurements
Type Time(ns)
Fill array (1000 elements) 148
Fill bit set(1000 elements) 261
Fill array (50 000 elements) 4669
Fill bit set(50 000 elements) 12758

77. Collections

78. Collections

79. Measurements
Type Time(ns)
New ArrayList() 3,6
emptyList() 2,4

80. Autoboxing

81. Measurements
Type Time(ns)
Array(100 elements) 58
List(100 elements) 390
Array(10 000 elements) 4776
List(10 000 elements) 48449

82. LIFO

83. LIFO
Stack
LinkedList
ArrayDeque

84. Stack

85. Measurements
Type Time(ns)
Stack(1000 elements) 5729
LinkedList(1000 elements) 7928
ArrayDeque(1000 elements) 4366
Stack(100 000 elements) 588770
LinkedList(100 000 elements) 773684
ArrayDeque(100 000 elements) 484280

86. Collections

87. 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

88. Reflection

89. Reflection
Type Time(ns)
instanceof 2,266
isAssignableFrom 2,146
== 2,401

90. Reflection

91. Measurements
Type Time(ns)
New object 3,0
Reflection 5,4

92. Reflection

93. Measurements
Type Time(ns)
Method call 0,3
Reflection 232

94. Measurements
Type Time(ns)
Method call 0,3
Reflection (cached) 3,1

95. Cloning

96. Measurements
Type Time(ns)
Clone 6,5
Direct copying 3,8

97. Sample

98. Lists

99. Measurements
Type Time(ns)
ArrayList (1000 elements) 4766
ArrayList (100 000 elements) 381707
LinkedList (1000 elements) 5504
LinkedList (100 000 elements) 504231

100. 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

101. Theory

102. Q&A
• Sergey Morenets, sergey.morenets@gmail.com