In this lesson, you will learn how to identify frequent heap allocations using the Unity Profiler to prevent stuttering caused by Garbage Collection.
When your game runs, it stores data in two main areas: the Stack and the Heap. The Stack is fast and manages itself, but the Heap is where Unity stores objects like strings, arrays, or classes. When you create new objects on the Heap frequently—especially inside your Update() method—you fill up memory rapidly.
Eventually, Unity’s "Garbage Collector" must pause your game to scan the Heap and delete these unused objects. This process is what causes those dreaded, tiny "micro-stutters" or frame drops.
Spotting Allocations in the Profiler
To stop these stutters, you first need to see them. Open the Profiler window (Window > Analysis > Profiler) while your game is running. Switch to the CPU Usage module and look for the GC Alloc column.
If you see a value higher than 0 bytes being generated every single frame, that is a red flag. For example, look at this common mistake:
void Update() {
// This creates a new string on the Heap every single frame!
string status = "Player Health: " + health;
Debug.Log(status);
}
Because + creates a new string object in the Heap every time it runs, the Garbage Collector has to clean it up constantly.
How to Optimize
The goal is to move allocations out of high-frequency loops. Instead of creating new objects every frame, use caching. If you need to display text, update an existing variable rather than creating a new one, or use a cached string if the value hasn't changed. By minimizing "GC Alloc" in the Profiler, you ensure that the CPU focuses on smooth gameplay rather than cleaning up memory.
Key Takeaway: Frequent allocations in your Update() loop force the Garbage Collector to trigger often, causing frame stutters; identify these in the Profiler's "GC Alloc" column and move them outside of per-frame logic.