Mark & Sweep Algorithm

Info

One of the Garbage Collection techniques,
it is a method of reclaiming memory by finding objects in memory that are no longer referenced.

Mark

Starting from root objects, find and mark all reachable objects.

• Object Creation: Mark as 0
• Graph traversal from all roots: Mark as 1

Root Objects

In garbage collection, they serve as the "starting point" and are a set of objects directly accessible by the program.

• Variables on the stack
• Global objects and variables
• Values stored in registers

Sweep

Remove unmarked objects (i.e., objects that are no longer reachable) from memory.

• Clean up objects marked as 0
• Initialize the marking bit of all objects (it will be changed back to 1 in the Mark phase)

Disadvantages

• The program's execution is temporarily suspended while garbage collection is performed.
• Fragmentation problem occurs
  • Available memory space is split, requiring defragmentation.

Reference

• https://m.blog.naver.com/sssang97/221567636644