Description of the issue:
When the download speed increases the frame rate decreases. I am main thread limited and it seems downloading scenery during flight also happens on the main thread and consequently reduces the frame rate any time scenery is downloaded.
[PC Only] Did you remove all your community mods/add-ons? If yes, are you still experiencing the issue?
Yes
FREQUENCY OF ISSUE
How often does this occur for you (Example: Just once, every time on sim load, intermittently)?
Any flight in a plane that struggles on performance in a busy area
REPRODUCTION STEPS
Please list clear steps you took in order to help our test team reproduce the same issue:
- Select a plane that is quite hard on performance
- Select a busy area to fly in
- Fly around, especially try moving the camera to trigger the game to download scenery
YOUR SETTINGS
[PC Only] Are you using Developer Mode or have you made any changes to it?
No
[PC Only] Many issues may be due to an outdated graphics card. Please state your Graphics Card Driver Manufacturer (NVIDIA, Intel, AMD) and Version:
NVIDIA 576.28
[PC Only] What other relevant PC specs can you share?
i7-11700f
3060 12gb
32gb ram
MEDIA
Please add a screenshot or video of the issue occurring.
[END OF FIRST USER REPORT]
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This isn’t a bug, it’s to be expected. Cpu is spending time downloading and storing the data and the processing it for use. This has been the case always in msfs2024 that every time there are large spikes in downloading data that the cpu time spikes, GPU usage drops and fps drop. I’ve seen this consistently and it’s one downside of the streaming data approach as compared to msfs2020.
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Correct me if I’m wrong, but the Rolling Cache should be ‘buffering’ the streamed data, allowing the CPU to process it more smoothly. Maybe OP’s Rolling Cache file is too small?
Maybe. I have tried a rolling cache of 0, 16, 32, and 64gb and it made no difference on my system. Every time it downloads large chunks of data I see a cpu spike and GPU usage and fps drop as measured by intel presentmon software. It’s not a bug and has always been there in msfs2024 at least on my system. I’d be curious if others see the same. By the way, this doesn’t happen in msfs2020 as it’s appears to be faster to pull the information from the local storage that was already downloaded. I’m on 1gb fiber internet too so I have concluded it’s just how the msfs2024 sim is going to operate and it’s noticeably worse during busy times of the day/week when more people are flying…a high server load like and it’s a shame it can’t be improved over time,
If you want to take a (really) deep dive into the Rolling Cache, read this thread by @nenenui.
I confess to not understanding half of it, but he sums things up at the end of each post in a way that make his conclusions understandable for a dummy like me. 
He recommends 100-256GB for the RC size.
That’s a LOT more than we were told was optimal for FS2020. But as you pointed out, the streaming model is a whole different animal, and by corollary, so is the Rolling Cache model.
What I find a little puzzling is how it could be both high download speed AND overworked servers. They seems counter to each other: When server load decreases my negotiated download speed should increase, and vice versa. OP is having problems when his downloads get faster. Maybe his network adapter is buffering too much data, and dumping it in large packets? That’s not something you normally would mess with.
This is a bug. I have 16 threads and the game chooses to use the one that is most limited to download and decompress data. This has nothing to do with the streaming only approach of 24 since 2020 also downloaded scenery on the fly and didn’t have this issue. Streaming data should be on a different thread than the main one.
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I have a rolling cache of 16gb
I am specifically talking about downloading scenery, which is all online in both 2020 and 24 but only 24 has this reduced frame rate when downloading. This is a bug since downloading and decompressing scenery is done on the main thread which is already limited instead of one of my 15 other threads.
I didn’t mean when the download is too quick, I meant any time it goes above zero I notice that the frame rate will drop in the FPS panel and then the download speed will spike. I have no problem with this in 2020 and that also downloads scenery on the fly so I reported this as a bug.