[kennethrc]

> Even something as simple as alt-tabbing lagged for seconds on an overpowered machine.

This may not be KDE's fault; I tracked these kinds of issues down to some bad tunable defaults.

I came up with this:

    ----
    cat /etc/sysctl.d/50-usb-responsiveness.conf
    #
    # Attempt to keep large USB transfers from locking the system (kswapd0)
    #
    vm.swappiness = 1
    vm.dirty_background_ratio = 5
    vm.dirty_ratio = 5
    vm.extfrag_threshold = 1000
    vm.compaction_proactiveness = 0
    vm.vfs_cache_pressure = 200
    # FIXME? 64K too big?
    vm.page-cluster = 16
    ----

I have fast everything, NVMe SSD onboard and others in Thunderbolt 4 enclosures and 32GB of RAM on my 12th-Gen i7 with 20 (6+14) cores; there should have been no reason for any stuttering and/or Alt-Tab slowness while doing large file copies and finally got fed up, did some research and experimentation and use the above and it's not happened since.

YMMV, but it's worth a try.

(Oh, and on-topic, I've had to try Wayland (vs. X11) on my KDE desktop 'cause it seems to handle switching monitors when I go from home to work better; jury's still out if I'm keeping it)

[deno]

You really only need dirty_ratio/bytes and dirty_background_ratio/bytes set to something lower than default. It also makes your progress bars show values closer to reality, especially when copying from fast to slow media.

Some distros already do set lower defaults, e.g. pop os:

https://github.com/pop-os/default-settings/blob/master_noble...

Bazzite: https://github.com/ublue-os/bazzite/blob/main/system_files/d...

[kennethrc]

> You really only need dirty_ratio/bytes and dirty_background_ratio/bytes set to something lower than default.

The vm.swappiness=1 was very necessary for me as well, and made as much difference as the dirties you'd mentioned.

I usually run Linus' master kernels (as I look for regressions in certain subsystems) and I know there's been some recent changes to the MM subsystem so this may explain some of the necessity for me.