multi-second lag/delay/latency accessing Overview / Activities screen

Affected version

• Debian 10 (buster) with Xorg
• gnome-shell 3.30.2-11~deb10u2
• HPC workstation with 8GB GPU, 2x POWER9 and 128GB RAM

Bug summary

Delay of multiple seconds accessing the Overview screen

Steps to reproduce

1. move the mouse to the word "Activities" on the top left
2. OR: press the key for the Overview screen (default is left compose key/Windows key)
3. Wait 2-3 seconds
4. Overview eventually appears

The problem occurs the same whether the mouse or compose key is used in step (1)

What happened

2-3 second delay at step 2

What did you expect to happen

Immediate response, especially on a workstation like this.

Relevant logs, screenshots, screencasts etc.

I had the GNOME performance monitor active while switching to the Overview, I could see that one CPU core shoots up to 100% and stays there for 2-3 seconds before the Overview screen appears.

There are many reports online in Reddit, Ask Ubuntu and other places. Some people speculate that there is a correlation between the number of open windows and the duration of the delay. In my case, I often have a lot of windows open, mainly because I contribute to a lot of different organizations and projects concurrently.

• https://askubuntu.com/questions/1182712/activites-overview-slow-to-appear
• https://www.reddit.com/r/gnome/comments/40o91x/is_there_a_fix_for_the_laggy_activities_screen/
• https://www.reddit.com/r/gnome/comments/4tsxyd/whats_the_cause_of_gnomes_lag_is_it_possible_to/

There is a related bug report about longer delays and a correlation with power status (battery/mains) #982 (closed)

As people use this part of the desktop so frequently it is really important to eliminate the delay. It makes both GNOME and Linux look like another OS when a problem like this is even occurring on such a powerful workstation. This machine has two POWER9 CPUs and 128GB over 8 memory channels.

As suggested in some complaints, I tried disabling animations (GNOME tweak tool), that didn't make much difference.

As a workaround, people can do some of the following things to avoid transitions to the full Overview screen:

• in the GNOME Tweak Tool, Extensions tab, enable the "Applications menu" and use that when possible
• in the GNOME Tweak Tool, Extensions tab, enable the "Workspace indicator" and use that when possible