From the moment you open up a website in your browser multiple virtual machines (VMs) are at work. The server generating the website might use Java, your browser executes JavaScript and maybe there is some Flash content running — with everything being executed in a VM. Virtual machines became increasingly important and popular after Google’s introduction of V8. We expect our code to run fast but let’s step back for a second and see how these complicated pieces of software work. With a better understanding of how your daily ActionScript or JavaScript code is being executed you might start coding a little different. Join Joa and dive deep into the the world of virtual machines. Learn about different garbage collection strategies and understand why those beasts behave the way they do.

1. VIRTUAL
MACHINES
FITC Amsterdam 2013 | Joa Ebert | 02/19/2013

2. JOA EBERT
@joa

14. Agenda
WHAT is a virtual machine?
WHY do we need them?
HOW do they work?
WHERE are the issues?

15. WHAT
is a virtual machine?

16. „A machine is a
tool that consists
of one or more
parts, and uses
energy to achieve
a particular goal.“
WIKIPEDIA

17. „A virtual machine (VM)
is a simulation of a machine
(abstract or real) that is
usually different from the
target machine (where it is
being simulated on).“ WIKIPEDIA

18. Programmers really love
to make it complicated ...

19. SYSTEM PROCESS
VIRTUAL VIRTUAL

20. CODE
EXECUTION
MEMORY MULTI
MANAGEMENT THREADING

21. WHY
do we need them?

22. PLATFORM AGNOSTIC

23. PROFILING AND
DEBUGGING IN
PRODUCTION

24. SANDBOXING
AND SECURITY

25. OPTIMIZATION

26. EXISTING
PROGRAMS
RUN FASTER WHEN
THE VM GETS
FASTER.
MORE SPACE FOR
INNOVATION.

27. HOW
do they work?

28. CODE
EXECUTION

29. FEEDBACK ABOUT
TYPES AND HOT
SPOTS
NATIVE
VM CODE
RUNTIME
CODE
INTERPRETER

30. HIDDEN
CLASSES
function Person(age, gender) {
this.age = age
this.gender = gender
}
var joa = new Person(26, „male“)

31. Person
function Person(age, gender) {
this.age = age
this.gender = gender
}
var joa = new Person(26, „male“)

32. age
Person Person
26 age
function Person(age, gender) {
this.age = age
this.gender = gender
}
var joa = new Person(26, „male“)

33. age gender
Person Person Person
26 age age
0x80f54644 gender
function Person(age, gender) {
this.age = age
this.gender = gender
}
var joa = new Person(26, „male“)

34. POLYMORPHIC
INLINE
CACHES
function isAdult(person) {
return person.age() > 17
}

35. POLYMORPHIC
INLINE
CACHES
function isAdult(person) {
return person.age() > 17
}

36. isAdult lookup Person::age
... return this.age
age()
...

37. isAdult Person::age
... if not Person
age() lookup()
...
return this.age

38. isAdult PIC stub Person::age
... if Person if not Person
age() Person::age() lookup()
... else if Robot
Robot::age() return this.age
else
lookup()

39. isAdult PIC stub
... if Person
age() return this.age
... else if Robot
Robot::age()
else
lookup()

40. SPECULATIVE
OPTIMIZATIONS

41. STATIC DYNAMIC
TYPING TYPING

42. def using[I <: { def close() }, O](stream: I)(f: I ⇒ O): O =
try {
f(stream)
} finally {
stream.close()
}
STRUCTURAL TYPING

43. mem ber thos e PICs?
Re
def using[I <: { def close() }, O](stream: I)(f: I ⇒ O): O =
try {
f(stream)
} finally {
stream.close()
}
STRUCTURAL TYPING

44. while(true) {
computeTheAnswerToTheUltimateQuestionOfLifeTheUniverseAndEverything();
}
DEOPTIMIZATION
AND OSR

45. DEBUG RELEASE

46. oracle.com/us/technologies/java/java7-renaissance-vm-428200.pdf

47. GARBAGE
COLLECTION

48. CONSERVATIVE PRECISE

49. 0x00 0x00 0x00 0x10 0x00 0x00 0x00 0x00
0x80 0x00 0x00 0x01 0x80 0x00 0x00 0x04
0xde 0xad 0xbe 0xef 0x00 0x10 0x00 0x00
MEMORY

50. 0x00000010 0x00000000
0x80000001 0x80000004
0xdeadbeef 0x00100000
MEMORY (DWORD ALIGNED)

51. 0x00000010 0x00000000
0x80000001 0x80000004
0xdeadbeef 0x00100000
MEMORY (DWORD ALIGNED)

52. 0x00000010 0x00000000
0x80000001 0x80000004
0xdeadbeef 0x00100000
MEMORY (DWORD ALIGNED)

53. 0x00000010 0x00000000
0x80000001 0x80000004
0xdeadbeef 0x00100000
MEMORY (DWORD ALIGNED)

54. 0x00000010 0x00000000
0x80000001 0x80000004
0xdeadbeef 0x00100000
MEMORY (DWORD ALIGNED)

55. Conservative GCs suck!

56. 1 1
REFERENCE
COUNTING

57. Reference counting sucks!

58. COPYING
COLLECTOR

59. FROM-Space
TO-Space

60. FROM-Space
TO-Space

61. TO-Space
FROM-Space

62. Copying collectors are really cool but for a
8GB heap they require 16GB total memory!

63. MARK &
COMPACT

64. Young Survivors Old
Generation Generation
EPHEMERAL GC

65. THREADING

66. CONCURRENCY PARALLELISM

67. SHARED ISOLATED

68. WHERE
are the issues?

69. ALL VMS ARE
CREATED
EQUAL.

70. ALL VMS ARE
CREATED
EQUAL. NOT.

71. JAVASCRIPT
IS NOT
JAVASCRIPT

72. J A V A
IS NOT
J A V A

73. PEOPLE MAKE AN
ARGUMENT FOR A
PARTICULAR VM
„Don‘t do this“ IS NOT
ALWAYS TRUE

74. STARTUP COSTS
ARE PAINFUL
FOR SHORT
RUNNING
APPLICATIONS

75. TODAYS
ADVICE
IS NOT
TRUE FOR
TOMORROW

76. BENCHMARKING
IS REALLY HARD.
MICROBENCHMARKS
ARE EVEN MORE
USELESS.

77. WITH GREAT
POWER
COME GREAT
EXPLOITS

78. GC DOES
NOT COME
FOR FREE

79. Is your GC
predictable?

80. MEMORY
vs.
SPEED

81. Write Code for the Future.
Don‘t try to outsmart
todays technology.

82. Always Remember:

83. Always Remember:
Math kicks everyones ass!

84. O(1)
O(log n)
O(n)
O(n log n)
O(n²)
O(n³)
...
O(x n)
O(n!)

85. THANK
YOU
Enj oy the party tonight and
FITC Amsterdam 2013 | Joa Ebert | 02/19/2013
b on voyage!