I just got updated to Plasma 6. So far, it seems like a downgrade from what I was using in 5. Everything is slower. I do have a 9 y/o computer, but 5 was running much better.
Just my observation.
Jason
I have a preference for a snappy interface - speeding up animations or disable them - is likely to provide a better experience.
I saw a comment indicating a member synced a an old netbook with 2GB ram to plasma 6 and it worked better than before.
It is a valid obversation for your system - but I don’t think you can generalize.
For everything I use, Plasma 6 is an overall improvement.
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There are definitely bugs, and certain features are still to be added — as will definitely happen by way of the future maintenance releases. Also, the moving around of items within the System Settings is a bit illogical in some cases. But in my personal experience, Plasma 6 is a major improvement over Plasma 5, and this is not exactly the fastest or most recent machine on the block either.
This computer has now just turned 5 years old — literally about 6 weeks ago — and it was already not the latest & greatest hardware anymore when I bought it, because this is an 8th-generation Intel i5, and the 9th generation was already being sold, with the 10th generation scheduled to arrive within a few months.
It did originally come with only one 8-GiB memory module installed — which was twice the amount my previous computer had — and after about 6 months, I had a second 8-GiB module put in. So not only did I then have 16 GiB of RAM, but now I also had dual-channel memory access, which did noticeably improve the snappiness and application loading time.
However — and this cannot be repeated enough — it is imperative that one updates/upgrades the right way, and given that the upgrade from Plasma 5 to Plasma 6 was so incisive, that one does one’s research and makes one’s preparations before executing the upgrade, i.e.:
- removing all third-party widgets and applets;
- switching all theming components back to the upstream-default Breeze;
- logging out of Plasma completely;
- logging in at a
tty; - emptying
~/.cache/; - if necessary, renaming all
~/.config/plasma*files and~/.config/Trolltech.confwith a.baksuffix; - shutting down
sddmby way ofsystemctl; - refreshing one’s mirror list and running the update process with
pacman; - rebooting; and…
- after logging in again, dealing with one’s
.pacnewfiles.
The problem is that virtually nobody does it that way, or even pays any attention to the Stable Updates announcement threads. 
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I had the same experience with my AMD Laptop, i found out that Wayland perform much better on Plasma6 when you own a AMD GPU.
No problem on X11 with my PC with a nvidia GPU.
You may want to switch when clicking bottom left while Login inside the SDDM.
Without knowing any specifics of your hardware, please note that there is currently at least one open issue that could have a significant impact on desktop effects (stutters etc.) if you are using a HDD for /home.
I guess it will be fixed with one of the next Kwin updates:
In my tests/usage of Plasma 6 on Wayland, everything worked out great so that I felt it was a big improvement to Plasma 5, even if I prefer to use Gnome for my daily needs.
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Thank you for all of the tips. I had a feeling that going from 5 to 6 was going to break some things, but I didn’t know it was going to make a performance hit. I’ll look into some of the things that have been suggested. I don’t get to keep up with proper use of Linux upgrades and news as I wish I could.
My hardware:
Intel i7-4790 K @ 4 GHz
32 GB RAM
Nvidia GeForce GTX 970 x 2 in SLI
3 monitors
A combination of SSDs and a HDD. System flies on SSD and /home on HDD
There you are.
You are doing something kinda silly to begin with that would negatively impact performance but also happens to land in an open bug.
There is not a general ‘Plasma 6 Performance Hit’.
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Why would he not feel it in Plasma 5 and feel it in Plasma 6? I find hard to believe this is the problem. I also have an HDD (an old one) as my home partition. I do use bcache with a SSD caching partition, but I doubt this would make such an impact.
There are two things which come in mind. One is baloo settings. If a lot of indexing is going on, there could be a performance hit with the HDD, and these settings could have been changed by the update (I have it turned off).
The second is sysctl settings. If there is a large amount of page memory (the machine does have 32GB) being written, the system can become sluggish because of the HDD.
So, I would suggest checking vm.dirty_background_bytes and vm.dirty_bytes, and, if possible, setup bcache with a SSD as caching device (I have writeback active too and it always worked very well).
For caching, I use a 24GB stripped (raid0) lvm partition for a 1TB disk drive, but a smaller partition (16GB) can work as well.
As for drity values, I use
vm.dirty_background_bytes=83886080
vm.dirty_bytes=167772160
These values are based on a 5 second write at USB 2.0 maximum speed, for synchronization purposes. Other values can be set, for example, based on the maximum speed of the HDD. The higher the values, the more data will be written as once, especially after large transfers. Smaller values have the advantage of minimizing data loss when something goes wrong, but increase write frequency. This is debatable as was debated a number of times. I’m not looking for another debate, just giving a suggestion.
Finally, before jumping into any of these suggestions, watch processes’ CPU load and disk activity, because there may be some process/application jamming the system.
The problem is that the Kwin effects are now written in QML instead of C++. While the plus is much easier to maintain and nicer effects, the downside is that the effects run in the QML VM which never actually retains the compiled QML bytecode in memory (RAM) between executions - instead it tries to be “fast” (i.e. faster than loading and parsing QML documents on every execution) by caching the compilation result in bytecode cache files on the hard drive.
A slow spinning drive with a lot of I/O can suffer a lot from that.
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This should be easily remedied by using /tmp for the cache, or at least, on systemd-based systems, because systemd sets up /tmp as a tmpfs by default.
Well, except...
… in (open)SUSE, but they’ve already long got their filesystem hierarchy completely wrong, to the point that it has become such a mess that nobody’s willing to fix it anymore.
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First of all, thanks for the explanation because I wasn’t aware of that. Second, I haven’t felt any sluggishness, and my system is way worse that the one of the OP. However, I do use very few effects and have them on high speed.
Well, there’s also vmtouch.
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One of the reasons I stopped using that several years ago was the piss-poor performance as compared most other distributions.
I started my Linux journey back in time with SuSE
- late 90’ies as a recall
- back then it was yast
- which as i recall still it the goto package manager
- then it went under the Novell umbrella
- I have tested tumbleweed - not impressive
- if one wants a system with commercial support - Red Hat is still the place to go
- that is an opinion
- I use Arch btw - blaaa
And should someone be interested - I offer commercial support for Manjaro - including a customized local mirror setup.
I liked Yast. I tried TW for a solid month and didn’t much care for it (I don’t recall why, specifically) so stuck with Leap for a year or so; spat the dummy over something (probably the performance) and moved to CentOS. I liked CentOS despite the Gnomification; probably due to the sensible decisions made at the time.
Works a treat. 
Plasma 6 - nightmare experience for me. Super-buggy. On my wife’s PC it broke down mechanism of desktop Icons - now only raster ones work properly - SVG don’t work at all (if I choose any Icon themes including Breeze almost all icons disappears).
Latte-Dock don’t work, Plasma panels flying around as they want (they can be at center or at the corner after boot), desktop freezes sometimes (you can’t choose any items on it for some time). In one of the profiles, all notifications appear right in the center of the desktop and can’t be moved away. Wayland don’t work properly (buggy as hell - useless), and I know it’s because Wayland and proprietary Nvidia drivers are incompatible, but I can’t stop using it, so I stick with X11 for now.
I don’t understand developers which don’t test upgrade from previous systems and configurations. Just finish code, test on clean system with literally default configuration and send to prod.
I have 2 PC with Manjaro and one laptop with Neon they all upgraded to Plasma 6 and I hate it. I even think of switching DE now. And I’m on Linux since 2003 - for twenty years now. I see hell.
You should probably have read the respective update announcement, and most of the issues you describe might have been avoided.
This is the relevant note from the Stable Update 2024-05-13 Announcement, originally: If you use KDE you better logout of your session and do the update via Pacman or Pamac in tty.
Search the forum (you did that, right?) and you’ll find many examples of others not taking the necessary precautions; and additionally, a few ways to recover from the situation. See the link at the top of this post for a general procedure.
Latte Dock is not supported in Plasma 6. I used it myself for a while; sad to see it go; that’s life, move on.
Cheers.
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Based on your information you have skipped the basics.
For example - lattedock is not compatible with plasma 6.
You should clear configs, cache, and remove all deprecated widgets, etc.
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And surely the slowness problem is due to high resource consumption, and it is most likely that baloo6 has not been disabled.
I do upgrade from tty. Bug with broken SVG-icons is not related to user configurations. I wiped out all configs on one of the user profiles (removed .local and .config folders completely) with no effect at all.
When I transited from KDE4 to KDE5 it was smooth, but this time it’s hell.
Also, I don’t know why do it try to switch to Wayland by default which is unusable with Nvidia (it’s flickering on some applications, XWayland works awful and almost all my wine apps which depends on 3D don’t work and have no workaround). And it was the only positive movement which was advertised for upgrading to Plasma 6.
Now I can’t find anything which works better on Plasma 6.