[2.1.17] Scenario Editor intermittently throttles at 30 UPS

[charredUtensil]

I've been using the scenario editor to test out arbitrary sub-assemblies in a test world, intending to play a new save once 2.1 is stable. Seemingly at random, the game sometimes starts failing to reach 60 UPS. What's really weird about this is that it seems to be "choosing" to run the game at a consistent UPS of either 31 or, occasionally, 47. This is a beefy top-tier gaming PC from 2023 running Windows 11 and I can usually get this file running well over 400. This file even runs fine on my garbage Thinkpad with Xubuntu on a microSD card. I don't see anything in the debug overlays that suggests a source of lag. Task Manager usually reports Factorio using 2% of my CPU.

Things that seem to cause the issue:
- Working near the edge of the generated space on the "Lab" surface (but not necessarily moving around too much)

Things that seem to resolve the issue:
- Changing the game speed via the UI
- Moving around significantly
- Pressing F5, which makes all the debug text appear (makes it very annoying to get a screenshot with it)

Random thoughts that may or may not be related:
- No mods. Just Space Age.
- My monitor is actually a TV and its refresh rate is capped at 30 FPS. Changing this doesn't seem to affect the bug, but UPS shouldn't be tied to FPS. It's also possible I messed with some display setting at some point while attempting to get the display to cap at 30 but I don't know what specifically that might be.
- I only use this computer for gaming, with Steam being the only other application open with Factorio.
- My Windows settings are fairly locked down in terms of privacy stuff.
- I did notice on an earlier 2.1 version that moving around the lab would cause the minimap to flicker quickly between green and magenta. This isn't happening any more, but maybe it was related?
- The save file has quite a few space platforms, but I haven't been messing with them lately and they've all been parked over Nauvis while this bug comes and goes.

[eugenekay]

The provided ZIP file is not a savefile from saves/; it is a compilation Zip including a logfile and a scenarios/ sub-folder.

In Map Editor --> Settings, disable Generate neighbor chunks. Do you still experience the slowdowns while moving near the Edge of Surfaces?

[charredUtensil]

I included files from `scenarios/` in the original post. I've attached an autosave from this world in this post as I see no other files in `saves/` corresponding to it. This was created in the Scenario Editor.

I tried disabling the setting and it did not change anything. The issue isn't necessarily caused while moving around. I just ran a test with the game completely idle, watching one of the sub-factories. The game spontaneously dropped to 30.6 UPS, then stayed at that exact level for at least ten seconds. I pressed F5 and immediately the UPS went back up to 60, and stayed there. The counter, being a rolling average, took about a second to transition between the two numbers but the effect on the actual game UI was instant.

Autosaves also seem to trigger this behavior sometimes, which is again separate from the usual Windows issue where the game pauses during saving. I would expect to see the game freeze and maybe the UPS counter briefly reflect the latency, but what actually happens is the "saving" bar appears, the UI freezes still showing 60 UPS, the "saving" bar disappears, and then the UPS counter ticks down to 30 and stays there indefinitely.

This also doesn't behave like I would expect a "normal" latency issue to behave. In a normal latency issue, I would expect to see UPS impacted, moving down from 60 and then fluctuating as the game struggles to keep up. This issue is like the game was suddenly toggled to half speed, then suddenly toggled back.

[charredUtensil]

Tested again while idle. An autosave occurred, which took 4 seconds to complete. UPS then dropped to exactly 30.0 again, stayed there for 34 seconds, then went back up to 60.

[charredUtensil]

OK: One more test and I can at least confirm that the root issue here is UPS being dependent on FPS in some sneaky way:

My monitor is set to a refresh rate of 30 Hz. At no point in testing have I observed UPS drop below 30.0
I set my monitor to 60 Hz. Factorio runs at 60 FPS. The issue stops occurring.
I set my monitor to 24 Hz. Factorio runs at 24 FPS. The issue starts occurring again, but this time drops to 24 UPS.

Now, I recognize that I am probably the one person on Earth who sets his gaming PC monitor to a low refresh rate on purpose, and not for performance reasons so I ran one more test to see if this would affect any sane person:

I set my monitor to 60Hz. I set the game speed to x2. Factorio runs at 60 FPS. While it does struggle to keep 120 UPS consistently, I do see the issue reproducing as there are stretches where the game suddenly drops to 60 UPS and stays there for a while. Thus, the bug is this:

If the game's target UPS is higher than FPS, the game can intermittently cap the UPS at FPS despite having the processing power to go much faster.

I set the autosave frequency to 1 minute and found this is triggered by autosaves about 10% of the time.

[Bilka]

I have to ask, do you have VSync enabled or disabled and does this behavior change if you toggle it?