What Happens When Stuttering Starts

Bug Reporting Hub Install, Performance & Graphics
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I have lost count of the number of posts documenting the stuttering problem. Briefly the stuttering problem happens at random times and places while flying. The FPS significantly, usually in half, for a short period of time. The stuttering stops suddenly and “normal” flying resumes. There have been so many reports that indicate the stuttering is not specific to any hardware, aircraft, location, weather, time of day, monitor resolution, graphics parameters, Community folder add-ones, or anything else.

Here is a screenshot taken during stuttering while flying yesterday. The items marked explain what happens when stuttering starts. The information here is very “Windows technical”. You do not need to know any of this to use MSFS.

#1 - Red Not Responding - MSFS is busy doing something else and cannot respond to the user inputs. This doesn’t last too long but definitely breaks the video stream processing. FPS is decreasing.

#2 - MSFS is reading into memory a large number of files at the same time. Notice the file names like “bush trip”. I am not flying in a bush trip and haven’t for months. Flight tutorials are being loaded into memory. The screen is not big enough to show the entire file list. (Note small scroll bar on the right.) Also, different files and different amounts of files are read into memory from the same subdirectories during other stuttering occurrences.

I have no idea what is triggering MSFS to read these files at this point or any point during the flight.

#3 - The performance graphs show the impact of these files being read by MSFS.

CPU utilization decreases because the amount of graphics processing is decreased while the files are being read into memory. Also, MSFS isn’t doing any processing of these files once they are loaded into memory.

Disk utilization is very high because of the large amount of files. File sizes vary and larger files take longer to read into memory.

Network is not busy. Sometimes there is a lot of network activity during the stuttering if scenery files are being downloaded into the rolling cache.

Memory utilization is growing as more files are shoved into memory.

#4 - Because of the large number of files MSFS is putting into memory, Windows has to make room for them quickly. Also, Windows doesn’t know how many files will be read into memory or exactly how much space will be needed. To prevent a complete system freeze, Windows moves some memory pages from RAM to the paging file. If MSFS needs any of those memory pages to continue running, Windows has to move them back into RAM. Because there already is a lot of disk activity, the moving of memory pages adds additional load.

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When the files have finished being read into memory, the stuttering stops, at least for awhile.

If the developers FPS counter is displayed during stuttering, it shows the the FPS is limited by the main thread. This file processing does limit the main thread as shown by the CPU utilization decrease.

Several users have posted decreased stuttering after reducing the object level of detail. The stuttering decreases because when the CPU is available during all this file activity, it is processing scenery files. Decreasing the graphics completely allows more frames to be processed during the file crunch.

Also, this is NOT the memory leak problem. When stuttering stops as described above, Windows cleans up any unused memory. The memory leak problem never restores the FPS.

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This is an interesting find.

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Can these files deleted via the content manager?

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Sure. I just went in and got rid of them all. Even if it doesn’t help, it freed up a couple GB of space:-)

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I don’t have Microsoft.FlightSimulator… folder under Appdata\Local\Packages.
If you are using the rolling cache, I suggest you to disable it. It’s well known that it causes stuttering.

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Deleted all of them, makes no difference

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That’s not the cause in this case either. There are bugs baked into the system and Asobo is working on it.

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Don’t delete any files. That is not the point. It is probably the entire MSFS package including aircraft, liveries, gauges, base scenery, all the objects and object textures. Eventually, when you’ve deleted all the MSFS files, there will be no more stuttering because there won’t be any MSFS left. If you’ve deleted any files, you might have to reinstall MSFS.

I have no idea what is causing the stuttering. I’m not making ANY changes until after a fix is delivered.

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Content from content manager can be deleted safely, as they are additional.

Deletions taken in the directory shouldn’t be done, that’s correct.

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GPU - I forgot to mention the GPU! Unfortunately, GPU information is only in the Task Manager. Performance Monitor has nothing. At the same time the snapshot was taken, Task Manager showed the GPU at a very low utilization because the CPU was sending fewer frames to display.

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One of the reasons (there could be many) the game could be reading this bunch of file, is if it was checking for updates, or integrity (DRM) for example. Usually this is something you’d only trigger when loading the game, not when playing it though (unless a bug is causing it to check every few minutes instead of once only).

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Another issue could be the VFS that needs to decrypt many files. You can’t just add files to encrypted drives, it’s like the secure folder used in MSFS. It needs to encrypt and decrypt files for use, and that is cpu work.

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That’s pretty much the same thing I see too. The past few evenings I decided to fly up the coast of France. Butter smooth amazingly the entire time. It is such an odd bug.

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It puzzles me that CPU utilization drops when the stuttering starts and then goes back up after the files are finished. If there is some sort of decryption or DRM going on, I think with the amount of files being read, all the processors in the CPU would crater. I think that even checksum or file integrity validation would take a lot of processing. Only Asobo knows and they aren’t talking.

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LOL here is the funny part I had partly good partly bad morning, so I had to leave for the day I started a flight at Kcle and flew to burke lakefront 5 min flight shut down logged the flight and left the plane sit there. 9 hours later still running at 45 FPS cool so I climb in the cockpit launch and didnt even make my turn around Cleveland. Stutter etc etc this is getting old fast. 1 week and 1 day and no definitive answer from on Asobo on this.

I knew it was probably going to be a rough start (hoping it wasnt) but this is just getting to the point of being sad…

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I saw that my last core was always maxed out at 100% whereas the other cores are at around 10-20%. Could it be that it is just an issue on how the workload is allocated to the available cores?
I figured this could be the case since the built in FPS counter always claims it is limited by the Mainthread.

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Windows distributes workload to the cores, not MSFS. If this is a workload distribution, it would be a Windows problem, not an MSFS problem.

The problem is the nature of the workload. For some reason, MSFS is reading a lot of lies into memory at the same time slowing everything down.

Yes, the FPS counter shows it is limited by the main thread which is correct. But what is limiting the main thread? The FPS counter doesn’t show anything that is limiting the main thread. Actually, the FPS counter doesn’t care what is liming the main thread. All it is saying that the FPS is low because the main thread isn’t sending frames fast enough to the GPU. In general the primary job of the GPU is to make the graphics frames and send them to the monitor. The CPU (main thread) takes care of everything else inside of MSFS. The FPS counter doesn’t have any visibility into “everything else”.

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Thank you for this detailed explanation! Very interesting. I also noticed that when I am flying Planes with glass cockpit, the frames go down by around 20 FPS, which makes sense since it is more work for the CPU. However I havent had this effect prior to SU3. Like literally the second I switch on the screens, the stutter party begins.
So I am wondering if it is a problem with the glass panels, the environment or a combination of both.

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Glass cockpits were a huge performance problem a few months ago but has been fixed with the adjustment parameter on the Graphics Option Seiings page.

I have no idea on why MSFS is reading so many files at once causing the stuttering.

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Thanks for the detailed analysis.

I found that there are 2 instances of the stuttering issue. One is triggered by location, and you will consistently get the problem in that location. These bad locations have a problem if you fly into them or if you spawn directly into the area. But you can fly out of the area and things return to normal.

The 2nd is a random stuttering event where it starts in an area that has previously been free from problems. I have found you can’t fly out of these (or if you can, the time required exceeded my patience) and that this requires a MSFS restart to fix. After the restart the same area is free from problems again.

In the recent video Asobo mentioned 2 things they had fixed so far, so I hope it covers both of these.

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