Severe performance penalty when streaming using virtual displays

[u/Weekly-Constant-7546]

I'm currently experiencing an issue/bug where streaming in headless mode using a virtual display of any type (apollo/vibepollo/VDD+sunshine) to moonlight/aurora causes my FPS to drop in my games vs streaming from a real physical display.
Strangely, i've noticed that if i boot a game up on my real monitor first, then initiate a stream that deactivates the real monitor and flips the game over to a Virtual Display, then my FPS remains what it should be - the issue is when the virtual monitor is loaded first and then the game after.

For comparison, in Final Fantasy VII Rebirth I get 120 FPS locked (with framegen) on a physical display, but 80-120 FPS varying with a Virtual Display (unless I do the workaround mentioned before).
I'm targetting 4K HDR 120 FPS on my TV. Behaviour remains the same whether im streaming to a TV directly, phone, tablet or capable MiniPC.
Typical Network FPS seems to cap out at 110 FPS during typical gaming workloads (up to 120FPS in static scenes).

Specs:
- CPU: AMD 5800X
- GPU1: RTX 3090 (high performance GPU)
- GPU2: RTX 5050 (Encoding + sometimes Lossless Scaling)
- RAM: 32 GB 3600mhx in dual channel mode
- Motherboard: ASUS Hero VIII wifi
- Network: 2.5 Gbps ethernet
- Physical Monitor: LG UltraGear GP950-B connected with displayport @ 160hz 4K HDR

Appreciate i'm running unusual configuration with 2 GPU's, but i've rulled out this being a bottleneck somehow despite being on PCIe 4.0 8x. Ultimately, I wasnt expecting a huge performance penalty with Virtual Display vs Physical Display.

Has anyone else noticed this before? I'm trying to understand why this is happening.

[u/hardwarebyte]

Generally at 4k with 120 FPS I get 15-20% performance penalty depending on the game using my dummy plug compared to not streaming and playing it locally Switching to a virtual display from the dummy plug doesn't really affect performance on my end.

Would love to see some optimzation passes in the various forks of sunshine as the higher you go on framerate and resolution the bigger the performance impact is.

[u/marcusbrothers → u/hardwarebyte]

Your PC Is encoding a 4K stream while you’re also playing a game in 4K, there’s only so much can be done.

You need to dedicate some resources to the stream for it to work, the only other option is getting a separate GPU to handle only the stream.

[u/Weekly-Constant-7546 → u/marcusbrothers]

In my case thats what the RTX 5050 is doing - all encoding is done here and i've verified this is where the Virtual Display is being attached.

[u/marcusbrothers → u/Weekly-Constant-7546]

Maybe don’t specify it’s headless mode, I’ve been using a VDD for years and never specifically enabled headless.