What is Unity's "UnloadTime"?

I am trying to optimize the startup speed of my Unity-based Augmented Reality app.

When looking at the Xcode logs, I saw that the app startup pauses for a while until it prints this:

UnloadTime: 3.068542 ms

Although it says “ms”, the noticeable delay is rather the same time in seconds. Sometimes, this pause even lasts 6 seconds or more.

So I am wondering what this “UnloadTime” actually is? I couldn’t find anything in the docs about it. Is there a way to optimize this time to get it down? I would also be interested in an explanation why it sometimes takes considerably longer (like double time 3s => 6s).

Wondering the same question, I get it very early in my app log, which is even weirder:

Mono path[0] = ‘C:/Prgdir/Gamecraft/GC_Mainline/Build/Development/StandaloneWindows64/Techblox_Data/Managed’
Mono config path = ‘C:/Prgdir/Gamecraft/GC_Mainline/Build/Development/StandaloneWindows64/MonoBleedingEdge/etc’
PlayerConnection initialized from C:/Prgdir/Gamecraft/GC_Mainline/Build/Development/StandaloneWindows64/Techblox_Data (debug = 0)
PlayerConnection initialized network socket : 0.0.0.0 55451
Multi-casting “[IP] 192.168.1.66 [Port] 55451 [Flags] 2 [Guid] 155353821 [EditorId] 2514521450 [Version] 1048832 [Id] WindowsPlayer(Seb-Sam) [Debug] 1 [PackageName] WindowsPlayer [ProjectName] Techblox” to [225.0.0.222:54997]…
Started listening to [0.0.0.0:55451]
Starting managed debugger on port 56821
Using monoOptions --debugger-agent=transport=dt_socket,embedding=1,server=y,suspend=n,address=0.0.0.0:56821
PlayerConnection already initialized - listening to [0.0.0.0:55451]
Initialize engine version: 2020.2.3f1 (8ff31bc5bf5b)
[Subsystems] Discovering subsystems at path C:/Prgdir/Gamecraft/GC_Mainline/Build/Development/StandaloneWindows64/Techblox_Data/UnitySubsystems
GfxDevice: creating device client; threaded=1
Direct3D:
Version: Direct3D 11.0 [level 11.1]
Renderer: NVIDIA GeForce GTX 1060 6GB (ID=0x1c03)
Vendor:
VRAM: 6052 MB
Driver: 27.21.14.5751
Begin MonoManager ReloadAssembly

  • Completed reload, in 0.319 seconds
    D3D11 device created for Microsoft Media Foundation video decoding.
    Slow Unity Logger added
    Initializing input.
    Input initialized.
    Initialized touch support.
    UnloadTime: 1.648800 ms
    can it be unloading of a scene?