What Are the Core Concepts of Memory Management and Garbage Collection?

Memory Management and Garbage Collection

Memory Regions

• Stack: Function call frames, local variables; automatically allocated/freed; fast
• Heap: Dynamic allocation (objects, arrays); managed by GC

GC Algorithms

Mark and Sweep

1. Start from root objects, mark all reachable objects
2. Sweep (collect) unmarked objects ❌ Can cause memory fragmentation

Reference Counting

Track how many references point to an object; collect when count reaches zero ✅ Immediate reclamation ❌ Cannot handle circular references (Python has a cycle detector)

Generational GC

Partition objects by age (Young / Old / Permanent)

• Most objects die young; focus on scanning Young Generation
• Used by JVM (Java) and V8 (Node.js)

Stop-the-World (STW)

GC pauses all application threads—the main source of latency spikes

• Modern GCs (ZGC, G1 GC) minimize STW pause times

Language Comparison

Language	GC Mechanism
Java	Generational GC (G1/ZGC)
Go	Concurrent Mark-Sweep
Python	Reference Counting + Cycle Detector
Rust	No GC; Ownership system at compile time