Garbage Collector Glossary

Short background notes on the general GC concepts the Garbage Collector and Precise Stack Scanning articles build on. Each page explains the concept on its own, then closes with one line on how OrionGC applies it.

Concept	Summary
Stop-the-world	All threads pause for the full duration of a collection
Mark-and-sweep	Mark what is reachable, sweep the rest in place
Moving vs. non-moving	Whether live objects can ever be relocated
Generations	Age-segregated heaps, and what a single generation avoids
Bump allocation	Allocation by advancing a pointer through fresh space
TLAB	Per-thread buffers that make the allocation fast path synchronization-free
GC roots	Where reachability starts
Precise vs. conservative scanning	Knowing which stack words are references, or guessing
Safepoint	Code locations where the compiler's tables describe the GC state exactly
Funclet	Exception handlers compiled as small separate functions with frames of their own
Finalization and resurrection	Cleanup code before reclaim, and dead objects becoming reachable again
Runtime object header	The bookkeeping word just before every object (hash code, thin lock)
ABA problem	Why lock-free code needs version tags when values can be recycled