[Bug]: 3.15.x is slow/slugish on Win11 23H2

[pzwahlen]

⚠️ Before submitting, please verify the following: ⚠️

• This is a bug, not a question or a configuration issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server and Desktop Client are up to date. See Server Maintenance and Release Schedule and Desktop Releases for supported versions.
• I agree to follow Nextcloud's Code of Conduct

Bug description

Hi,

When I first upgraded to 3.14.0 on my Win11 23H2 the UI was very slow. It was most visible when scrolling down the folder view:

Moving the scrollbar always takes 1-2 seconds (seems like freezing for a short while). I then downgraded all my clients to 3.13.4, which is working fine.

Today I decided to test with both 3.14.1 and the latest nightly build (windows-20241020.msi) and the situation is the same, hence this bug report.

I read that there have been issues with dark theme but it is the same with dark/light theme.

I experienced this on 2 clients (a HW one and a VM) connected to the same account. One is using Virtual Filesystem, the other is fully synced.

Regards!

Steps to reproduce

1. Open settings
2. Move to an account
3. Scroll down the folder list

Expected behavior

scrolling should be smooth

Which files are affected by this bug

n/a

Operating system

Windows

Which version of the operating system you are running.

Windwos 11 23H2

Package

Official Windows MSI

Nextcloud Server version

30.0.1

Nextcloud Desktop Client version

3.14.x

Is this bug present after an update or on a fresh install?

Updated to a major version (ex. 3.3.6 to 3.4.0)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

Are you using an external user-backend?

• Default internal user-backend
• LDAP/ Active Directory
• SSO - SAML
• Other

Nextcloud Server logs

No response

Additional info

No response

[pzwahlen]

I'm quite surprised this hasn't been reported by others.

Here is 3.13.14 working as expected when moving around the folder list:
https://github.com/user-attachments/assets/0bfb9720-190d-4031-9a4f-4d6fa8487898

And here is the same folder list on 3.14.2:
https://github.com/user-attachments/assets/767c2a1d-e1bb-4685-b3f2-14af4948411a

Again, going back to a light theme doesn't change this behaviour. Both have been recorded in Win11 23H2. The largest diff for me is QT5 vs. QT6.

I have also looked at the threads activity using Process Explorer:

• On 3.13.4, moving the list mostly shows activity of the nextcloud.exe thread. The Qt5Core.dll threads remain idle most of the time.
• On 3.14.2, moving the list shows activity on the nextcloud.exe thread as well as 8 Qt6Core.dll threads.

[pzwahlen]

Someone told me this would be solved by restarting explorer.exe, unfortunately for me this is not the solution.

Rebooting or restarting explorer.exe do not solve this problem.

The Windows 11 desktop is also otherwise idle.

I have the feeling that the folder list takes an unusual amount of time to be created. This might depend on the number of top-level folders, which is 57 in my case. Maybe a shorter list would be faster, but this is still a major regression when compared to 3.13.x.

Cheers!

[Sveeeeeen]

I can confirm this issue. I've experienced significantly poor performance with version 3.14.x. Reverting to 3.13.4 has resolved the problem and is working smoothly for me.

I am using Windows 11 23H2.

[ikros1]

Sorry for posting wrong conclusion before, because at that time through other wrong comments and tried to restart explorer.exe method briefly restored a short period of normal side of the comments, later on the windows 10 status bar extreme lag and upload bandwidth is only 90k or so, and page animation effect is delayed seriously, retried the above method has no effect so deleted the comments. The system version I am using now is windows 22H2 ,back to use nextcloud desktop 3.13.4 without the above problem.

[BaneusCatrix]

I can also confirm this bug in version 3.14.2 on windows 10 22H2. When the sync is running, the sync speed drops below 1kb/s and the start menu is not usable until nextcloud.exe is killed. A downgrade to version 3.13.4 fixed this behavior.

[pzwahlen]

Just a quick one to share that 3.14.3 does not solve this problem.

Is there a way to "profile" the UI and find out where all those CPU cycles are being used ?

[pzwahlen]

3.15 is still crazy slugish when working in the settings UI. Any click brings Qt6Core.dll to the roof. I have therefore changed the title of this issue.

Today, I realized that even just moving the Window can trigger this problem, so it is most likely an issue between Qt6 and Windows.

Anyclue for further troubleshooting ?

That means back to 3.13.x again, which I hope will remain supported until we find a fix for this.

Despite that, thanks again for the hard work on this Windows client!

[pzwahlen]

I can add that these are only CPU spikes following any single mouse interaction with the settings UI. There is no disk IO generated.