High CPU use when focus is on kitty window under Wayland

[tristpinsm]

I've noticed that when a kitty window is focused, the CPU used by the gnome-shell and ibus-daemon processes shoots up to over 100%. It goes back down when the focus moves to any other window. This only happens with kitty as far as I can tell, and it goes away if I set linux_display_server x11 in kitty.conf.

To Reproduce
Steps to reproduce the behavior:

1. Set the focus to a kitty window under Wayland.
2. Watch the CPU use of gnome-shell and ibus-daemon go up in top.

Environment details

kitty 0.25.0 created by Kovid Goyal
Linux tristXPS 5.17.7-arch1-1 #1 SMP PREEMPT Thu, 12 May 2022 18:55:54 +0000 x86_64
Arch Linux 5.17.7-arch1-1 (/dev/tty)

DISTRIB_ID="Arch"
DISTRIB_RELEASE="rolling"
DISTRIB_DESCRIPTION="Arch Linux"
Running under: Wayland
Frozen: False
Paths:
  kitty: /usr/bin/kitty
  base dir: /usr/lib/kitty
  extensions dir: /usr/lib/kitty/kitty
  system shell: /bin/zsh
Loaded config files:
  /home/tristan/.config/kitty/kitty.conf

Config options different from defaults:
font_family          Inconsolata Regular
font_size            12.0
shell_integration    frozenset({'no-cursor'})
Added shortcuts:
	shift+page_up → scroll_page_up
	shift+page_down → scroll_page_down
Colors:
	background           #485867   
	color0               #485867   
	color1               #b38686   
	color10              #87b386   
	color11              #aab386   
	color12              #868cb3   
	color13              #b386b2   
	color14              #86b3b3   
	color15              #e3efef   
	color16              #d8bba2   
	color17              #b39f9f   
	color18              #5a6d7a   
	color19              #6d828e   
	color2               #87b386   
	color20              #98afb5   
	color21              #c9dbdc   
	color3               #aab386   
	color4               #868cb3   
	color5               #b386b2   
	color6               #86b3b3   
	color7               #b0c5c8   
	color8               #8299a1   
	color9               #b38686   
	cursor               #c9dbdc   
	foreground           #b0c5c8   
	selection_background #c9dbdc   
	selection_foreground #485867   

Important environment variables seen by the kitty process:
	PATH                                /usr/local/bin:/usr/bin:/var/lib/snapd/snap/bin:/usr/local/sbin:/var/lib/flatpak/exports/bin:/opt/fv:/usr/lib/jvm/default/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl
	LANG                                en_CA.UTF-8
	SHELL                               /bin/zsh
	DISPLAY                             :0
	WAYLAND_DISPLAY                     wayland-0
	USER                                tristan
	XDG_MENU_PREFIX                     gnome-
	XDG_SESSION_DESKTOP                 gnome
	XDG_SESSION_TYPE                    wayland
	XDG_CURRENT_DESKTOP                 GNOME
	XDG_SESSION_CLASS                   user
	XDG_RUNTIME_DIR                     /run/user/1000
	XDG_DATA_DIRS                       /home/tristan/.local/share/flatpak/exports/share:/var/lib/flatpak/exports/share:/usr/local/share/:/usr/share/:/var/lib/snapd/desktop

Additional context
The problem persists with kitty --config NONE.

[kovidgoyal]

Sigh, more awesomeness from GNOME 42. When I return from travelling I
will investigate if there is something I can do in kitty's Wayland
backend to work around GNOME. At least I can reproduce this one, instead
of it being because of timing issues in mutter.

[fezboy]

This seems to have been introduced in #4855, as it is present at 11343d4, but not 6c628bc

[kovidgoyal]

Yes, quite likely, maybe @page-down wants to take a look, otherwise I will investigate when I return.

[v-ji]

At least for me, running kitty with --debug-keyboard shows a flood of events that don’t appear with X11:

...
text-input: enter event
text-input: done event: serial: 11 current_commit_serial: 11
on_key_input: glfw key: 0x0 native_code: 0x0 action: RELEASE mods: none text: '' state: 1 
text-input: updating cursor position: left=16 top=16 width=9 height=19
updated pre-edit text: ''
text-input: done event: serial: 12 current_commit_serial: 12
on_key_input: glfw key: 0x0 native_code: 0x0 action: RELEASE mods: none text: '' state: 1 
text-input: updating cursor position: left=16 top=16 width=9 height=19
updated pre-edit text: ''
text-input: done event: serial: 13 current_commit_serial: 13
on_key_input: glfw key: 0x0 native_code: 0x0 action: RELEASE mods: none text: '' state: 1 
text-input: updating cursor position: left=16 top=16 width=9 height=19
updated pre-edit text: ''
text-input: done event: serial: 14 current_commit_serial: 14
on_key_input: glfw key: 0x0 native_code: 0x0 action: RELEASE mods: none text: '' state: 1 
text-input: updating cursor position: left=16 top=16 width=9 height=19
updated pre-edit text: ''
...

There’s multiple hundreds of these per second.

[page-down]

Sorry for introducing this issue. However in the meantime I am also temporarily unable to access the test environment and I may need more time to come back.

If I remember correctly, the send_text mentioned in the association above is just a request to kitty to clear the pre-edit text, not sure why it would affect other processes and lead to a higher cpu usage. I may have missed something.

[kovidgoyal]

Seems like kitty is clearing pre-edit text, reporting it to gnome, gnome is telling it to clear the pre-edit text again in an endless loop. Probably just ignore the request to clear pre-edit text if it is already cleared, but I have to look at it in more detail when I have some time

[mo8it]

I am on Fedora Silverblue, the problem did only appear after the upgrade today to Gnome 42.1.
I did boot into the last image to verify that the issue is only on Gnome 42.1 and this is the case.
The upgrade that did cause this is the following:

Upgraded:
  gnome-classic-session 42.0-1.fc36 -> 42.1-2.fc36
  gnome-shell 42.0-3.fc36 -> 42.1-2.fc36
  gnome-shell-extension-apps-menu 42.0-1.fc36 -> 42.1-2.fc36
  gnome-shell-extension-common 42.0-1.fc36 -> 42.1-2.fc36
  gnome-shell-extension-launch-new-instance 42.0-1.fc36 -> 42.1-2.fc36
  gnome-shell-extension-places-menu 42.0-1.fc36 -> 42.1-2.fc36
  gnome-shell-extension-window-list 42.0-1.fc36 -> 42.1-2.fc36
  gtk-update-icon-cache 3.24.33-1.fc36 -> 3.24.34-1.fc36
  gtk3 3.24.33-1.fc36 -> 3.24.34-1.fc36
  mutter 42.0-6.fc36 -> 42.1-2.fc36

I hope that this is somehow helpful :)

[Gabriel-Alves-Cunha]

Hi, I'm on Fedora Linux 36 (Workstation Edition) with GNOME 42.1 on Wayland.
I also just had this problem when I noticed it was only when kitty was on focus.
I was using the most updated version and then I downgraded to 0.24.4 and the problem was gone.
Just came here to file a bug and saw this one :)

[mo8it]

@kovidgoyal

I don't want to put any pressure, but can you please make a release with the fix soon? Thanks :)

[kovidgoyal]

Just use the nightly builds

[gitaarik]

Thanks, the issue disappeared with the nightly build :)