Fragmentation on a managed object when using Finalizer

Unity: Mono

As Designed

2023.1.X

2022.2.X

2021.3.X

The GC Unity currently uses is not a moving GC, so fragmentation is possible. Types with finalizers can cause additional fragmentation, as those objects must live a bit longer - waiting for their finalizers to be run. So unfortunately this is expected behavior. As we move to use the CoreCLR runtime, Unity will use a moving GC which will handle heap fragmentation much more effectively.

Reproduction steps:
1. Open the attached project "ReproProject"
2. Build and run the project (File > Build and Run)
3. Open Window > Analytics > Memory Profiler
4. Take a capture
5. Go to \Package\Runtime\RuntimeValues.cs
6. Uncomment the commented lines (finalizer)
7. Repeat 2, 3, and 4 steps
8. Compare both captures
9. Take a look at the difference of “Empty Fragmented Heap Space”

Expected result: The “Empty Fragmented Heap Space” difference is little or non
Actual result: The “Empty Fragmented Heap Space” noticeably differs between captures

Reproducible with: 2021.3.16f1, 2022.2.2f1, 2023.1.0a25
Could not test with: 2020.3.42f1 (Library\PackageCache\com.unity.memoryprofiler@1.0.0\Editor\Containers\MetaDataHelpers.cs(70,82): error CS8124: Tuple must contain at least two elements)

Reproducible on: Windows 10 Enterprise 21H2

Notes:

Reproducible on Android

Fragmentation on a managed object when using Finalizer

Unity: Mono

As Designed

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Fragmentation on a managed object when using Finalizer

Unity: Mono

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As Designed

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Description

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