User description:

When I run two windowed standalone instances to test multiplayer, the unfocused window gets about 2-5 fps...but if I focus on it, smooth 120fps, yet the opposite screen is now only getting 2-5fps. The interesting thing is, if I unfocus BOTH screens at the same time, both standalone windows are now reading 120FPS! I've never seen this before and apparently nobody else has either. And it seems to be on any type of UE4 project when running multiple standalone instances. I've even tested a basic template project. PIE version is just fine but I'm using seamless travel, so I must use Standalone mode to test. It's nearly impossible to test multiplayer when the unfocused window is lagging soooo far behind.

Attempted workarounds:

  1. Played a high-end game like Doom Eternal on Ultra settings with FPS active and unfocused it (in case it's my GPU). FPS did not drop.
  2. Unchecked "Use Less CPU when in Background" in the editor settings. That did not change anything
  3. Capped FPS to 60 in the project settings. Did not change anything.
  4. Checked Smooth Framerate. Did not do anything.
  5. Went into Nvidia global settings and changed V-Sync on and off. Did not change anything
  6. Went into Nvidia global settings and changed all settings to max performance. Did not change anything

In //UE4/Release-4.24 cl 11590231 no more than 1 Standalone window will appear regardless of what Number of Players is set to. Currently trying to get that to work to test for regression.

This doesn't seem to be happening in //UE4/Release-4.23 cl 10478456, where the framerates of the focused and unfocused window are not the same, but the difference is much smaller. e.g. 100 fps & 70 fps in 4.23 vs 200 fps & 30 fps in 4.25. For these reasons I am listing this as a regression.

Steps to Reproduce
  1. Create a blank third person project
  2. Open the dropdown menu next to Play
  3. Set number of players to 2
  4. Play as standalone game
  5. Once the game windows are open, open the console on each and enter Stat FPS
  6. Separate the windows so you can clearly see the FPS values for each
  7. Focus one Window
  8. Unfocus both windows

When one window is focused, it displays at max FPS while the other window runs much lower. When neither window has focused they both display at about the same FPS

Both windows run at highest FPS per device hardware

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Won't Fix
ComponentUE - Rendering - RHI
Affects Versions4.244.254.26
CreatedAug 25, 2020
ResolvedJun 8, 2022
UpdatedJun 9, 2022