Ruby Under The Hood

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About me

Guelph ES&C Grad – spring 2014

Currently employed at IBM as aRuntime Technologies Software Dev

Twitter: @craiglehmann

Ruby Under The Hood

http://lolsnaps.com/upload_pic/EveryTimeILookUnderTheHoodOfACar-97946.jpg

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Program compilation

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Program compilation

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Program compilation

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Program compilation

3.times do |n|

puts nend

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Program compilation

Tokens:3.times do |n|

puts nend

puts

ndo

end

3 dot times

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Program compilation

AST3.times do |n|

puts nend

puts n

3 times

call

block

command

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Program compilation

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The Ruby Interpreter?

The Ruby Interpreter implements a virtual machine.

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Bytecode Interpreter

The main VM execution loop. Maps bytecodes to executable native instructions. Implements a virtual stack machine. Individual bytecodes implemented in C.

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Ruby is a Stack Machine!

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Push Down Stack

1 + 2

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Push Down Stack

1 + 2 Push 1Push 2opt_plus

Bytecodes:

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Push Down Stack


Bytecodes:

1Push 1

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Push Down Stack


Bytecodes:

1Push 1

2Push 2

1

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Push Down Stack


Bytecodes:

1Push 1

2Push 2

3opt_plus

1

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Call Stack example and compiled method

def do_thingsputs "Hello

World"end

PutselfPutstring “Hello World”opt_send_simple

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Three Stacksdef do_things

puts "Hello World"end


C Stack VM Stack Ruby Call Stack

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World"end


call_method

C Stack

exec_core…

main()

VM Stack Ruby Call Stack

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World"end


call_method

C Stack

exec_core…

main()

opt_send_simple putsVM Stack

“hello World”self

Ruby Call Stack

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World"end


call_method

C Stack

exec_core…

main()



putsRuby Call Stack

do_things

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Three Stacks

call_method

C Stack

exec_core…

main()



putsRuby Call Stack

do_things

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What does this look like in the Ruby’s VM?

putsRuby Call Stack

do_things


World"end

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putsRuby Call Stack

do_things


World"end

PCControl Frame

SPSelftype

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putsRuby Call Stack

do_things


World"end

PCControl Frame

SPSelftype

putselfputstring “Hello World”opt_send_simple

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putsRuby Call Stack

do_things


World"end

PCControl Frame

SPSelftype

putselfputstring “Hello World”opt_send_simple



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Class lookup? What happens when you want to create an object?

class Person

end

p = Person.new()

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Class lookup? What happens when you want to create an object?class Person

end

p = Person.new()

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Class lookup? What happens when you want to create an object?

class Person

end

p = Person.new()

Person = "Craig"

#Warning: already initialized constant person

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Intro to garbage collectionWhat is garbage collection?Different types of garbage collection algorithmsMark & Sweep demo

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What is garbage collection?

Automatic memory management

Manually managing memory is hard!

Aggregate freeing memory & object destruction operations

Gives the illusion of unlimited memory

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Different types of garbage collection algorithms

Reference Counting• Keep a count along with each object indicating how many references it currently

has. An object with 0 references can have it's memory re-used.• Cannot manage cyclically referenced objects.

Tracing Algorithms• keep track of which objects are in use by recursively tracing objects referring to

other objects, starting from a root set of objects.

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What does it mean to die

• An object consumes one resource, memory.• When an object becomes unreachable, it can never be used again.• Cycles are collected together, the mutator cannot access these

object.• Sweeping objects means adding it’s memory to a list for reuse.• What about when an object consumes more than just one resource?

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Mark and Sweep Demo

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Mark and Sweep Demo

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Mark and Sweep Demo

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Mark and Sweep Demo

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Mark and Sweep Demo

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Mark and Sweep Demo

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Mark and Sweep Demo

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Mark and Sweep Demo

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Object Finalization

• Some objects may have operations that need to occur pre/post collection

• e.g. file object

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Execution Environment

Architecture of a Managed Runtime

Platform Abstraction Layer

Garbage Collector

Diagnostic Services

Source Code Bytecode/ASTCompiler

Just-In-Time Compiler

Interpreter

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Garbage Collector

Diagnostic Services



Interpreter

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Garbage Collector

Diagnostic Services



Interpreter

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Garbage Collector

Diagnostic Services



Interpreter

Interpreter context Thread context

Language callstack

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Garbage Collector

Diagnostic Services



Interpreter

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Garbage Collector

Diagnostic Services



Interpreter

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Garbage Collector

Diagnostic Services



Interpreter

Thank You!Twitter: @craigLehmann

Email: [email protected]

Ruby Under The Hood

Engineering

Transcript of Ruby Under The Hood