memory_management.md

Memory Management

Python

视频链接

Everything is a object in Python.

Python is a dynamically typed language. So there is no need to specify the type.

memory component

• heap
  • the objects and instance variables are created on heap
  • when an onject in heap is not reference anymore, it is removed immediately. The algorithm used for Garbage Collection is called Reference Counting.
• stack
  • the methods and variables are created on stack.
  • store reference to object on heap
  • a new stack frame is created on invocation of a funcition/method.

JAVA

• stack
  • method invocations
  • local variables: variables declared inside a method
    • primitive variable: integers, decimals or characters
    • reference to non-primitive variable
• heap (garbagr-collectable heap)
  • all objects live here.
  • garbage collector
    • generations:
      • young generation
        • minor garbage collection: young generations, 'stop the world event' - all thread stop and wait
      • old generation
        • major garbage collection: 'Stop the World' event
      • permanent generation

Variables stored in stacks are only visible to the owner Thread, while objects created in heap are visible to all thread.

C++

Operation on stack is one CPU instruction, which is easy and efficient.

Operation on heap is a bunch of things.