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Ruby Under The Hood

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craig lehmann

The document provides an overview of how Ruby programs are compiled and executed. It discusses how Ruby source code is tokenized and turned into an abstract syntax tree (AST) before being compiled into bytecode. It then describes how the Ruby interpreter implements a virtual machine that maps bytecode instructions to native operations. Key aspects covered include Ruby using a stack-based execution model, the interaction between the C stack, virtual machine stack, and Ruby call stack, and how garbage collection works through mark and sweep to reclaim unused memory.

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About me 1 Guelph ES&C Grad spring 2014 Currently employed at IBM as a Runtime Technologies Software Dev Twitter: @craiglehmann
Ruby Under The Hood http://lolsnaps.com/upload_pic/EveryTimeILookUnderThe HoodOfACar-97946.jpg
Program compilation 3
Program compilation 4
Program compilation 5
Program compilation 6 3.times do |n| puts n end
Program compilation 7 Tokens: 3.times do |n| puts n end puts ndo end 3 dot times
Program compilation 8 AST 3.times do |n| puts n end puts n 3 times call block command
Program compilation 9
The Ruby Interpreter? The Ruby Interpreter implements a virtual machine. 10
Bytecode Interpreter The main VM execution loop. Maps bytecodes to executable native instructions. Implements a virtual stack machine. Individual bytecodes implemented in C. 11
12 Ruby is a Stack Machine!
Push Down Stack 13 1 + 2
Push Down Stack 14 1 + 2 Push 1 Push 2 opt_plus Bytecodes:
Push Down Stack 15 1 + 2 Push 1 Push 2 opt_plus Bytecodes: 1 Push 1
Push Down Stack 16 1 + 2 Push 1 Push 2 opt_plus Bytecodes: 1 Push 1 2 Push 2 1
Push Down Stack 17 1 + 2 Push 1 Push 2 opt_plus Bytecodes: 1 Push 1 2 Push 2 3 opt_plus 1
Call Stack example and compiled method 18 def do_things puts "Hello World" end Putself Putstring Hello World opt_send_simple
Three Stacks 19 def do_things puts "Hello World" end Putself Putstring Hello World opt_send_simple C Stack VM Stack Ruby Call Stack
Call Stack example and compiled method 20 def do_things puts "Hello World" end Putself Putstring Hello World opt_send_simple call_method C Stack exec_core main() VM Stack Ruby Call Stack
Call Stack example and compiled method 21 def do_things puts "Hello World" end Putself Putstring Hello World opt_send_simple call_method C Stack exec_core main() opt_send_simple puts VM Stack hello World self Ruby Call Stack
Call Stack example and compiled method 22 def do_things puts "Hello World" end Putself Putstring Hello World opt_send_simple call_method C Stack exec_core main() opt_send_simple puts VM Stack hello World self puts Ruby Call Stack do_things
Three Stacks 23 call_method C Stack exec_core main() opt_send_simple puts VM Stack hello World self puts Ruby Call Stack do_things
What does this look like in the Rubys VM? 24 puts Ruby Call Stack do_things def do_things puts "Hello World" end
What does this look like in the Rubys VM? 25 puts Ruby Call Stack do_things def do_things puts "Hello World" end PC Control Frame SP Self type
What does this look like in the Rubys VM? 26 puts Ruby Call Stack do_things def do_things puts "Hello World" end PC Control Frame SP Self type putself putstring Hello World opt_send_simple
What does this look like in the Rubys VM? 27 puts Ruby Call Stack do_things def do_things puts "Hello World" end PC Control Frame SP Self type putself putstring Hello World opt_send_simple opt_send_simple puts VM Stack hello World self
Class lookup? What happens when you want to create an object? 28 class Person end p = Person.new()
Class lookup? What happens when you want to create an object? 29 class Person end p = Person.new()
Class lookup? What happens when you want to create an object? 30 class Person end p = Person.new() Person = "Craig" #Warning: already initialized constant person
Intro to garbage collection What is garbage collection? Different types of garbage collection algorithms Mark & Sweep demo 31
32 What is garbage collection? Automatic memory management Manually managing memory is hard! Aggregate freeing memory & object destruction operations Gives the illusion of unlimited memory
33 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.
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 its memory to a list for reuse. What about when an object consumes more than just one resource? 34
Mark and Sweep Demo 35
Mark and Sweep Demo 36
Mark and Sweep Demo 37
Mark and Sweep Demo 38
Mark and Sweep Demo 39
Mark and Sweep Demo 40
Mark and Sweep Demo 41
Mark and Sweep Demo 42
Object Finalization Some objects may have operations that need to occur pre/post collection e.g. file object 43
Execution Environment Architecture of a Managed Runtime 44 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter
Execution Environment Architecture of a Managed Runtime 45 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter
Execution Environment Architecture of a Managed Runtime 46 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter
Execution Environment Architecture of a Managed Runtime 47 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter Interpreter context Thread context Language callstack
Execution Environment Architecture of a Managed Runtime 48 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter
Execution Environment Architecture of a Managed Runtime 49 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter
Execution Environment Architecture of a Managed Runtime 50 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter
Thank You! Twitter: @craigLehmann Email: craigl@ca.ibm.com

More Related Content

Ruby Under The Hood

  • 1. About me 1 Guelph ES&C Grad spring 2014 Currently employed at IBM as a Runtime Technologies Software Dev Twitter: @craiglehmann
  • 2. Ruby Under The Hood http://lolsnaps.com/upload_pic/EveryTimeILookUnderThe HoodOfACar-97946.jpg
  • 7. Program compilation 7 Tokens: 3.times do |n| puts n end puts ndo end 3 dot times
  • 8. Program compilation 8 AST 3.times do |n| puts n end puts n 3 times call block command
  • 10. The Ruby Interpreter? The Ruby Interpreter implements a virtual machine. 10
  • 11. Bytecode Interpreter The main VM execution loop. Maps bytecodes to executable native instructions. Implements a virtual stack machine. Individual bytecodes implemented in C. 11
  • 12. 12 Ruby is a Stack Machine!
  • 14. Push Down Stack 14 1 + 2 Push 1 Push 2 opt_plus Bytecodes:
  • 15. Push Down Stack 15 1 + 2 Push 1 Push 2 opt_plus Bytecodes: 1 Push 1
  • 16. Push Down Stack 16 1 + 2 Push 1 Push 2 opt_plus Bytecodes: 1 Push 1 2 Push 2 1
  • 17. Push Down Stack 17 1 + 2 Push 1 Push 2 opt_plus Bytecodes: 1 Push 1 2 Push 2 3 opt_plus 1
  • 18. Call Stack example and compiled method 18 def do_things puts "Hello World" end Putself Putstring Hello World opt_send_simple
  • 19. Three Stacks 19 def do_things puts "Hello World" end Putself Putstring Hello World opt_send_simple C Stack VM Stack Ruby Call Stack
  • 20. Call Stack example and compiled method 20 def do_things puts "Hello World" end Putself Putstring Hello World opt_send_simple call_method C Stack exec_core main() VM Stack Ruby Call Stack
  • 21. Call Stack example and compiled method 21 def do_things puts "Hello World" end Putself Putstring Hello World opt_send_simple call_method C Stack exec_core main() opt_send_simple puts VM Stack hello World self Ruby Call Stack
  • 22. Call Stack example and compiled method 22 def do_things puts "Hello World" end Putself Putstring Hello World opt_send_simple call_method C Stack exec_core main() opt_send_simple puts VM Stack hello World self puts Ruby Call Stack do_things
  • 23. Three Stacks 23 call_method C Stack exec_core main() opt_send_simple puts VM Stack hello World self puts Ruby Call Stack do_things
  • 24. What does this look like in the Rubys VM? 24 puts Ruby Call Stack do_things def do_things puts "Hello World" end
  • 25. What does this look like in the Rubys VM? 25 puts Ruby Call Stack do_things def do_things puts "Hello World" end PC Control Frame SP Self type
  • 26. What does this look like in the Rubys VM? 26 puts Ruby Call Stack do_things def do_things puts "Hello World" end PC Control Frame SP Self type putself putstring Hello World opt_send_simple
  • 27. What does this look like in the Rubys VM? 27 puts Ruby Call Stack do_things def do_things puts "Hello World" end PC Control Frame SP Self type putself putstring Hello World opt_send_simple opt_send_simple puts VM Stack hello World self
  • 28. Class lookup? What happens when you want to create an object? 28 class Person end p = Person.new()
  • 29. Class lookup? What happens when you want to create an object? 29 class Person end p = Person.new()
  • 30. Class lookup? What happens when you want to create an object? 30 class Person end p = Person.new() Person = "Craig" #Warning: already initialized constant person
  • 31. Intro to garbage collection What is garbage collection? Different types of garbage collection algorithms Mark & Sweep demo 31
  • 32. 32 What is garbage collection? Automatic memory management Manually managing memory is hard! Aggregate freeing memory & object destruction operations Gives the illusion of unlimited memory
  • 33. 33 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.
  • 34. 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 its memory to a list for reuse. What about when an object consumes more than just one resource? 34
  • 35. Mark and Sweep Demo 35
  • 36. Mark and Sweep Demo 36
  • 37. Mark and Sweep Demo 37
  • 38. Mark and Sweep Demo 38
  • 39. Mark and Sweep Demo 39
  • 40. Mark and Sweep Demo 40
  • 41. Mark and Sweep Demo 41
  • 42. Mark and Sweep Demo 42
  • 43. Object Finalization Some objects may have operations that need to occur pre/post collection e.g. file object 43
  • 44. Execution Environment Architecture of a Managed Runtime 44 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter
  • 45. Execution Environment Architecture of a Managed Runtime 45 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter
  • 46. Execution Environment Architecture of a Managed Runtime 46 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter
  • 47. Execution Environment Architecture of a Managed Runtime 47 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter Interpreter context Thread context Language callstack
  • 48. Execution Environment Architecture of a Managed Runtime 48 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter
  • 49. Execution Environment Architecture of a Managed Runtime 49 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter
  • 50. Execution Environment Architecture of a Managed Runtime 50 Platform Abstraction Layer Garbage Collector Diagnostic Services Source Code Bytecode/AST Compiler Just-In-Time Compiler Interpreter