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Unity Engine

Tracking garbage collection allocations

Monitor when your application performed garbage collection.
Read time 3 minutesLast updated 13 days ago
Unity has the following tools to keep track of memory allocations:

Tracking allocations with the CPU Usage module

To track garbage collection allocations with the CPU Usage Profiler module, perform the following steps:
  1. Open the Profiler window (Window > Analysis > Profiler).
  2. Collect some performance data.
  3. Select a frame in the CPU Usage Profiler module.
  4. In the module details pane, open the Hierarchy view, and inspect the GC.Alloc column.
The GC.Alloc column displays the number of bytes that Unity allocated on the managed heap for the selected frame and thread.
Allocations can occur on all threads so you might want to use the thread selection drop down to check out other threads than the main thread. You can also use the Timeline view and keep an eye out for the 
GC.Alloc
samples, which are colored bright magenta.
Tip
Use the Call Stacks mode to enable the full call stack traces for 
GC.Alloc
samples. Call stacks give you precise details of where the garbage collector made the allocation without needing to use Deep Profiling mode, which might impact performance.

Tracking allocations with the Memory module

You can use the Memory Profiler module to track garbage collection memory allocations, but it only provides a high-level overview of where Unity allocated memory. For detailed information on memory usage in your application, use the Memory Profiler package.
To track garbage collection memory allocations with the Memory Profiler module, perform the following steps:
  1. Open the Profiler window (Window > Analysis > Profiler).
  2. Collect some performance data.
  3. Select a frame in the Memory Profiler module.
  4. In the module details pane, inspect the GC allocated in frame statistic.
The Managed Heap statistic displays the amount of memory that the garbage collector managed, and it includes memory that Unity might have allocated and reused in subsequent frames. This means that the sum of the 
GC.Alloc
samples over all frames doesn't total how much the managed memory grew in that time.
The GC allocated in frame statistic diplays the amount of memory that was allocated in this frame. This amount might be higher than the CPU Usage module displays in the GC.Alloc column of the Hierarchy view. This is because the 
GC.Alloc
statistic includes allocations made across all threads and also within Editor only samples, or as part of the 
EditorLoop
. The Hierarchy view only displays one thread at a time and hides the allocations made in Editor only samples by default and collapses the code running as part of the 
EditorLoop
unless the profiler targets the Editor and not Play mode.
Important
To get the most accurate information, profile your application on a development build on the target platform or device you want to build to. The Unity Editor works in a different way to a build, and this affects the profiling data. For example, the 
GetComponent
method always allocates memory when it's executed in the Editor, but not in a built project.

Additional resources