Developer Notes

GC and the mark phase in particular is very slow in editor. All the optimizations are in cooked builds where the mark phase should be super fast.


Garbage Collection is causing noticeable hitches on whatever interval it is run on. This is noticeable in the UE4 Profiler, as you will see a spike every X amount of seconds, depending on how often you have GC running.

Attached image provided by the user shows the hitches in question as well.

Found in 4.11.1 binary. Reproduced in Main CL 2933897.

Steps to Reproduce

1. Open the test project located here: [Link Removed]
2. PIE
3. Press end after ~12 seconds (this will show 4 hitches as GC is set to run every 3 seconds)
4. Open UnrealFrontend with the -messaging parameter
5. Click the Session Frontend tab
6. Click the Profiler tab
7. Click the Load button and open the UE4Stats file you created in step 3

Result: Noticeable hitches can be seen every 3 seconds (which is when garbage collection is set to run)

Expected: No hitches would occur.

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Won't Fix
ComponentUE - Foundation - Core
Affects Versions4.11.14.12
Target Fix4.12
CreatedApr 11, 2016
ResolvedApr 13, 2016
UpdatedFeb 5, 2017
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