Server Authority | UpdatePredictedHashes stalls ~750 ms of thread-time per frame on Intel CPUs — 12 FPS at 2 ms ping, AMD unaffected

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In 2 places with Server Authority enabled, we noticed that across Intel CPUs, the client becomes basically unplayable, while AMD players are perfectly fine

6 of us (3 Intel, 3 AMD) joined the same game. The 3 Intel players were lagging like crazy, one even crashing, while all 3 on AMD were fine. On my client I was at ~12 FPS with 86 ms CPU frames while GPU time was 0.52ms and ping was 2ms

When opening the micro profiler, almost all of the frame time is in Simulation/UpdatePredictedHashes which results in ~750 ms of thread time per rendered frame spread across the 16 RBX worker threads

To replicate, you can use this repo with an already premade server authority example GitHub - MrChickenRocket/Server-Authority-Tutorial-Cakeman: Roblox server authority tutorial using a custom character and smooth visuals · GitHub

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In addition, we noticed the same behavior in roblox’s own template Racing - Server Authority Template | Play on Roblox

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Furthermore, no lag occurs when playtesting in studio

2 of the intel cpus that were used in the testing were

  1. Intel Core Ultra 7 265KF
  2. i9-13900K
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bump this happens intermittently but im not sure what the exact reason could be other than cpu brand

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Great report. Thank you. Investigating.

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thank you thank you thank you!