Insane performance degradations with Scene Management turned on (NetworkPostLateUpdate)

[Squashi11]

Description

Turning on Scene Management insanely decreases performance and increases cpu times

Reproduce Steps

Toggle Scene Management and observe NetworkPostLateUpdate in profiler (LAG)

Actual Outcome

Turning on Scene Management halts performance

Expected Outcome

No / Minimal performance impact

Screenshots

1. Scene without Scene Management

2. Scene with Scene Management

Environment

• OS: Windows 11 Editor
• Unity Version: Unity 6000.2.12f1
• Netcode Version: 2.7.0 (newest)
• Netcode Topology: Client-Server

Additional Context

Discovered thanks to #3742 and turning on Scene Management. We spawn a lot of network objects in our game dynamically during the game.

[NoelStephensUnity]

Hi @Squashi11,

We spawn a lot of network objects in our game dynamically during the game.

If you have Multiplayer Tools installed, then I would disable the profiling and message metrics when doing any profiling.

You might also look at your network prefabs you spawn the most and determine if you want the Scene Migration Synchronization enabled on all of them (i.e. do you want to synchronize when they change scenes or if they never will then disable that property). The default value is for this to be enabled (which really there should be a way to default that to disabled, but until then you might want to disable that for any network prefabs that don't need that feature as it can become expensive when you have hundreds up to 1000+ spawned objects).

Other than those two specific areas that would be the most likely culprits for that stage in the player loop update, I would need a screenshot of the expanded NetworkPostLateUpdate invocation with that portion of the tree having the most expensive sub-methods invoked within (and if they have sub-methods those too) so we can narrow down specifically where that time is being spent?

[Squashi11]

Turning off scene migration synchronization from the spawned gameobjects seem to fix the issue! Thanks a lot.
( I think the default value might be better off set as disabled)

[Squashi11]

This is a deep profile after I turned off the network object setting on all of those spawned objects but there are still some objects that have them enabled with the scene synchronization.

[NoelStephensUnity]

Good to hear that resolved your issue.

This is something I will look into making this setting's default customizable.
(It would most likely not be looked into until sometime in 2026 since there is a way to prevent it from happening)

I will, however, push an update to the documentation that will include notes on this setting and the impact it can have on performance before closing this issue out.

👍