CPU lag spike found in game

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Every once in a while rarely, my CPU will have a full on lag spike where I can’t use my keyboard or mouse for a few seconds before it comes back which can lead to a few embarrassing situations, the problem is that I can’t exactly show any photos or such because it’s so rare that I can only describe it… randomly in games, for 2 through 5 seconds, my CPU will turn way up for however long before dropping back down to normal, it has made games significantly hard and unplayable

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Are you sure it is not just your internet?

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I’m sure, my internet is quite fine, and stable… I’m pretty sure It’s something on Roblox’s end… even in studio sometimes. The other thing I really notice is that even with graphics low, it still happens to lag. Usually it’s in games with loading stuff, but it also happens where the game doesn’t need to load much. It’s really bothering me.

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I forgot to mention this as well, sometimes with VC on it seems to lag frankly more, which doesn’t make sense since VC technically isn’t CPU driven (unless I could be wrong, correct me on that)

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That’s interesting. We typically do the following:

  1. Open the microprofiler so you can see it at the top of the screen.
    https://create.roblox.com/docs/performance-optimization/microprofiler
    Press Ctrl+F6 OR go to Esc → Settings → scroll down → Microprofiler → On.
  2. Then just keep playing. If you ever experience a 2-second lag, immediately after it goes away, press Ctrl+P to pause data collection in the microprofiler (you can also click the small Pause button in the black top bar, but you might miss the moment).
  3. Then, in the top menu, click Dump → 512 frames.

An HTML file will be generated in the same folder where your logs are usually stored.
It will have a name like: microprofile-20251022-211355.html

If you share it, it might shed some light on what exactly took so long.

I understand this isn’t exactly advice on how to fix the issue - rather, I’m sharing how we usually track it down ourselves.

As for the VC theory - that’s an interesting one. It could indeed be the cause, since it runs on a separate thread and might have synchronization issues with the others.

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