Unity Game Optimization - Third Edition

Value types and reference types

Not all memory allocations we make within Mono will go through the heap. The .NET Framework (and, by extension, the C# language, which merely implements the .NET specification) has the concept of value types and reference types, and only the latter needs to be marked by the GC while it is performing its Mark-and-Sweep algorithm. Reference types are expected to (or need to) last a long time in memory due to their complexity, their size, or how they're used. Large datasets and any kind of object instantiated from a class instance is a reference type. This also includes arrays (regardless of whether it is an array of Value types or reference types), delegates, all classes, such as MonoBehaviour, GameObject, and ...