On one of my systems, the application dashboard plasmoid causes the plasmashell process to use from 25% to 50% CPU, and kactivitymanagerd to use nearly the same amount at the same time. Plasma is made completely unresponsive, to the point that to remove the plasmoid I had to kill plasma and edit the plasmoids config file. All the rest (KWin etc.) is working well. This happens at least from 5.4.0, but it may have happened before too. I have no idea if this is due to a particular application dashboard setting: I was not able to test further, since it locks as soon as it starts. More details can be found in the thread reported in the URL field and below. According to this KDE forum thread: https://forum.kde.org/viewtopic.php?f=289&t=121533&sid=3ad603c3cb524e0838090b603e1983f5&p=341700#p341700 I'm not the only one having this problem. Reproducible: Always
I also had the exact same problem, removing the app dashboard from ~/.config/plasma-org.kde.plasma.desktop-appletsrc made plasma responsive again. The thing is, before all this I have used the "Application Menu", but now when I add it to my panel plasmashell will constantly consume 17% CPU (quad core i5), but everything seems to be responsive. Only the "Application Launcher" behaves normally, no abnormal CPU usage. When I switch to the App Dashboard then my panel and desktop freezes again and plasmashell hogs alot of CPU. The issue started yesterday, when I installed 2 new plasmoids ("Network monitor" and "Resources monitor") and a game called "Globonation 2" through the official Arch repositories. First I installed the plasmoids, but they seemed to work fine, no issues. I even have added them again right now, and plasmashell is idle at 0-3% CPU. A bit later I installed that Globo 2 game and when I first started it plasmashell immediately froze. I rebooted, logged in but plasmashell would still freeze. Only way to get it back was to remove the app dashboard. Would it help if I attach some output of gdb, as described here?: https://forum.kde.org/viewtopic.php?f=289&t=124690#p328669
gdb output might be extremely helpful to pinpoint what it's busy with, yep! Profiling with perf-top too.
I'm a Linux noob, if you give me an example perf-top command then I can try, in the meantime I will get some gdb output as described in the forum link, for both cases the app dashboard and app menu.
Created attachment 94545 [details] gdb output of plasmashell + app dashboard I attached the gdb output of plasmashell with the app dashboard. Funny thing is that as soon as I entered the 'detach' command, plasmashell suddenly became responsive! I can even open the dashboard and CPU usage is quite normal.
Created attachment 94548 [details] gdb output of plasmashell + app menu So I switched to the app menu again and everything was still responsive but plasmashell was at 17% CPU usage. I have again attached gdb to plasmashell and here is the output. Hope it is useful and let me know if there is anything else to improve the output... like, should I install some debug symbols?
Please try the following: Right-click each of the 'Recent' categories and disable them (or do it in the applet config dialog). The problem seems to be stemming from KActivities code, which those categories use. If the problem goes away by disabling them, we've narrowed the cause down a bit.
Yes, that has definitely helped! I removed them from the app menu as well as the app dashboard and now they both behave normally, no more freezes or abnormal CPU usage.
Adding Ivan to CC (KActivities maintainer)
Another user here affected by the same bug on Plasma 5.4 with Application Dashboard. I too can confirm the problem goes away after removing 'Recent' categories.
Ivan tells me this was fixed on master recently.