The Worst KDE Bug I've Ever Tracked Down...and how you can work around it!

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In this video, I document a very annoying KDE Plasma 6 bug, how I tracked it down, how to reproduce it, and how it's possible to work around it.
The bug causes KDE to fully hang for several seconds when using Alt+Tab, Window Overview, and Tiling Editor (and possibly others). It affected me and Brodie Robertson, and involves hard drives and caching!
KDE Bugzilla link: bugs.kde.org/show_bug.cgi?id=...
My website: acidiclight.dev/
Support me on Patreon: / acidiclight (NEW!)
Follow me on Mastodon: mastodon.social/acidiclight
I'm Michael, the lead programmer of Restitched by Trixel Creative. Alongside that and developing other games, I occasionally like to make videos about programming, game development and LittleBigPlanet logic. If that's something you're interested in, then perhaps that big red button might help you see some more of it. :)

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Опубликовано:

13 май 2024

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Комментарии : 61

@-KillerHawk- Месяц назад

We went from viewing the terminal from the stratosphere to inspecting individual pixels lmao 5:42

@-KillerHawk- Месяц назад

Anyway thanks for your contributions to kde, bug fixes like this are what keep the project feeling clean for users like me!

@acidiclight Месяц назад

Lol joys of being blind, I can actually say "Enhance!" and things do actually become more detailed.

@zirkoni42 Месяц назад

3:41 Sorts by modification time, tries to find a directory by name

@jirkasvitil2762 Месяц назад

I abonded kde several years ago because of how it works on HDD. It had similar lags but because baobab did some caching. I cannot use kde because they just keep BREAKING it. Everyone is bitching about GNOME for a good reason but the derived enviroments like cinnamon never broken on me in the way Kde did every time I tried it.

@Aoitori365 Месяц назад

i hope they fix this because not everyone can get highspeed storeage

@InfinityN Месяц назад

What? You have to go out of your way to even get spinning storage these days. SSDs are not expensive anymore provided you're not looking at TBs of storage.

@nomkid8880 Месяц назад

@@InfinityNthis is very tunnel-vision

@acidiclight Месяц назад

Two 4TB SSDs are far more expensive for very little benefit in my use case than two 4TB HDDs.

@InfinityN Месяц назад

@@acidiclightyes but this proves that you didn't read the comment. Most people don't need that kind of storage for their home directory.

@acidiclight Месяц назад

@@InfinityN Some people do. Including me. And that should never result in my compositor hanging because of excessive misuse of a persistent disk cache.

@karpfenboy Месяц назад

i had to reboot a VM like 4 or more times today and was wondering why this keeps happening lol glad you found out and shared!

@no_name4796 Месяц назад

Honestly i installed kde 6 on an old device and it was just near windows level of slow. I love kde6, and it's the version that convinced me to leave gnome, but damn that ram is getting eaten!

@skykingjason Месяц назад

I promise I'm not trying to be rude, but I've tried like 5 times to understand what you said at 0:17 and I still have no clue

@acidiclight Месяц назад

I'd help ya out but I have such a fear of hearing my own voice that I don't even remember what I said lol and don't wanna watch to check D:

@undefinedchannel9916 Месяц назад

you will never out-richie the Richie.

@szaszm_ Месяц назад

"as a bug in program, you will never out-ritchie the ritchie" one of his nicks is ritchie, so @acidiclight is referring to himself.

@acidiclight Месяц назад

@@szaszm_ Yep! That's what I say as a way of self-motivating myself when I start trying to hunt a really tricky bug. Way of reminding myself that, no matter how hard it gets to find, there's always a solution to a problem.

@Crigence Месяц назад

The combination of the video subject and his extremely nerdy voice is funnier than it should be to me

@szaszm_ Месяц назад

It's not as bad here, but it definitely does happen even on nvme. It used to be worse, not sure if it's because of Plasma 5, or if I turned off some desktop effects over time.

@perz1val Месяц назад

you are insane for using that scaling, I fullscreened the video on 32" and it is still way too small

@acidiclight Месяц назад

That's why I zoom in. If I were to scale up the screen itself, it'd offer me no benefit whatsoever as I'd need to scale up to 2000% (not hundred, thousand) to even remotely be able to read. I'd then have no room to do anything.

@Jeka476 Месяц назад

Video starts at 3:00

@PatrikTheDev Месяц назад

Thank you, he keeps yapping too much

@acidiclight Месяц назад

Would you prefer I don't talk? Because I'd be happy to redo the video with nothing but 009 Sound System.

@SimGunther Месяц назад

@@acidiclight I think comments like that (stuff I used to point out) point to disorganized thoughts such that the video doesn't get straight to the point. You and many other RU-vidrs like TheCherno or Someordinarygamers don't have to get condescending or salty about comments like that. If for anything, a brief mention (no longer than 20 seconds) of the main players and the demo of the issue seen on other people's machine would suffice before the deep dive via the terminal emulator 😊

@acidiclight Месяц назад

@@SimGunther fair. Still think it'd be funny to redo the video with a text editor and 009 sound system lol

@user-lj4lo7cx7m Месяц назад

@@acidiclightplease do the 009 video

@batlin Месяц назад

I think this was happening to me a few days ago -- when triggering "Present windows" it would just freeze solid for a couple of seconds until I hit escape about a million times in frustration. Lasted for a couple of hours and then just went away. [edit] Not sure now -- from the description here it seems like it shouldn't just fix itself. My ~/ is mounted on a crypt partition though, so I can imagine it bottlenecking if KWin is absolutely hammering disk I/O in that cache dir.

@Pothanenos 12 дней назад

Interesting video, thanks for the showcase. I would suggest getting to the point a bit faster. (Also the scaling thing is a bit nauseating, maybe use a bigger font size and stop the zooming? )

@acidiclight 12 дней назад

I cannot get the font size large enough for me to be able to see it, that's why I'm zooming in.

@anon_y_mousse Месяц назад

Every once in a while I get weird slowdowns, so thanks for pointing out another possible reason. I'll try deleting kwin's cache and see if that eliminates it. I only within the last year or so moved to Slackware 15 from 14.2+{tons of hacks}, and I found that a weird scrolling bug from konsole got fixed finally. So maybe I should update more than once every decade.

@jansn12 Месяц назад

deleting the cache won't help. the QML bytecode for the effects is stored there and will always be there when they are loaded. You'll have to move it to an SSD or if you don't have one to ramdisk. the good news here is .cache/kwin/qmlcache is small! on my system

@ultimatedarkkiller7215 Месяц назад

IVE BEEN SUFFERING WITH THAT AND THOUGHT IT WAS MY TRASH LAPTOP Also, i have a SATA SSD and no spinning drives, but if it is being used it still locks up some times.

@sergioornaque7943 Месяц назад

How big is your monitor???

@acidiclight Месяц назад

2x32inch 4K displays side-by-side

@Matmas Месяц назад

Idea: You could also try using writeback instead of writethrough as a workaround without SSD. Example: create a dedicated ext4 filesystem and use `tune2fs -o journal_data_writeback /dev/sdXY` and mount that under $HOME/.cache. You might lose some data in case of power failure but if it is used just for $HOME/.cache it might not matter. I am assuming the slowdown comes from waiting for disk writes.

@acidiclight Месяц назад

I did consider that, and I was actually going to try it. That was the night I accidentally corrupted my home volume and had to start over, because of this exact bug hanging Kwin for several hours I wasn't patient enough to wait. D:

@user-in2cs1vp6o Месяц назад

Goddamn kwin saboting itself all along

@5Hydroxytryptophan Месяц назад

I'm using a NVMe and Plasma 6 lags like crazy.. I'm sure there are multiple issues. Plasma 5 was blazing fast and fluid.

@acidiclight Месяц назад

Is it the same kind of hanging wiith the same three effects? Since the bug's based on disk busy-ness (how much it's being read from / written to at once), and not necessarily disk throughput, if you're also affected by this bug then I'd have a theory in your case.

@5Hydroxytryptophan Месяц назад

It's a bit difficult to follow the video and figure out what's exactly lagging, as it's often zoomed in too far. Kickoff lags every time, sometimes it does not slide out completely and I have the "Fall Apart" effect enabled. It's problematic even without the effect. The Kickoff lag happens on Intel/Nvidia hybrid and AMD dGPU. Okay, never mind.. while writing this I figured out it was adaptive sync.

@bruyh-ff6sg Месяц назад

i thought this was normal...

@hburke7799 Месяц назад

making UI dependent on disk latency?? wow...

@acidiclight Месяц назад

Unfortunately it happens. It's a mistake even video games can make, just think any time you play a game that freezes while saving or loading in a new area.