SteamOS 3.17.5 ruins the performance of ReDream emulator, if not using Steam Linux Runtime

[pizzadude]

Your system information

• Steam client version: 1756942958
• SteamOS version: 3.17.5 Beta
• Opted into Steam client beta?: No
• Opted into SteamOS beta?: Yes
• Have you checked for updates in Settings > System?: Yes

Please describe your issue in as much detail as possible:

On SteamOS stable, ReDream emulator (latest linux dev build), runs at a locked 60fps, with the Rayman 2 game, and other games. In SteamOS 3.17.5, it ruins the performance of most/every game in ReDream, including Rayman 2, making it run at 30-40fps with heavy audio stuttering. I noticed if I set the compatibility layer to "Steam Linux Runtime" it fixes the issue.

Steps for reproducing this issue:

1. Upgrade to SteamOS 3.17.5 Beta
2. Download https://redream.io/download/redream.x86_64-linux-v1.5.0-1133-g03c2ae9.tar.gz and extract
3. Launch redream and play a game such as Rayman 2
4. Notice extremely bad performance
5. Switch to Steam Linux Runtime for ReDream
6. Notice it runs properly

[smcv]

Switch to Steam Linux Runtime for ReDream

Switch how, in what user interface, from what, to what? I think your steps to reproduce are missing a few.

"Steam Linux Runtime 1.0" and "Steam Linux Runtime 3.0" are compatibility tools that are available in Steam. Were you using one of those? (There is no compatibility tool that is just named "Steam Linux Runtime", although the UI used to use that name for what's now referred to as SLR 1.0.)

Was this perhaps added to Steam as a non-Steam game (shortcut), with the bad / reduced-performance configuration being to run the emulator directly on SteamOS with no particular compatibility layer, and the good / high-performance configuration being to run it under one of the "Steam Linux Runtime" compatibility tools?

Or if not that, then what?

Whenever Steam launches a (Steam or non-Steam) game, you should find that it logs the full command in ~/.steam/steam/logs/console_log.txt. It looks something like this, on one long line:

[2025-10-02 12:49:21] /bin/sh\0-c\0/home/deck/.local/share/Steam/ubuntu12_32/steam-launch-wrapper --oom-score-adjust 900 -- /home/deck/.local/share/Steam/ubuntu12_32/reaper SteamLaunch AppId=2210092502 -- "/usr/bin/flatpak" "run" "--branch=stable" "--arch=x86_64" "--command=/app/bin/chrome" "--file-forwarding" "com.google.Chrome" "@@u" "@@" --window-size=1024,640 --force-device-scale-factor=1.25 --device-scale-factor=1.25\0

Please copy/paste the command that is launched with bad performance, and the command that is launched with good performance.

[pizzadude]

Bad performance: [2025-10-02 11:32:38] /bin/sh\0-c\0/home/deck/.local/share/Steam/ubuntu12_32/steam-launch-wrapper --oom-score-adjust 900 -- /home/deck/.local/share/Steam/ubuntu12_32/reaper SteamLaunch AppId=3686562782 -- "/home/deck/Applications/redream/redream"\0

Good performance (Steam Linux Runtime 3.0) [2025-10-02 11:36:20] /bin/sh\0-c\0/home/deck/.local/share/Steam/ubuntu12_32/steam-launch-wrapper --oom-score-adjust 900 -- /home/deck/.local/share/Steam/ubuntu12_32/reaper SteamLaunch AppId=3686562782 -- '/home/deck/.local/share/Steam/steamapps/common/SteamLinuxRuntime_sniper'/_v2-entry-point --verb=waitforexitandrun -- "/home/deck/Applications/redream/redream"\0

This is a non-steam game (linux native emulator for Dreamcast games). Running with no compatibility layer in latest SteamOS = bad performance. Running with any of the Steam Linux Runtimes, but I chose Steam Linux Runtime 3.0 = good performance. This didn't happen in previous versions of SteamOS.