High CPU usage per tab in Ghostty on Manjaro Linux

[plinkr]

I compiled the current version of Ghostty with zig build -p $HOME/.local -Doptimize=ReleaseFast

Ghostty 1.0.1-dev+0000000

Version
  - version: 1.0.1-dev+0000000
  - channel: tip
Build Config
  - Zig version: 0.13.0
  - build mode : builtin.OptimizeMode.ReleaseFast
  - app runtime: apprt.Runtime.gtk
  - font engine: font.main.Backend.fontconfig_freetype
  - renderer   : renderer.OpenGL
  - libxev     : main.Backend.io_uring
  - GTK version:
    build      : 4.14.5
    runtime    : 4.14.5
  - libadwaita : enabled
    build      : 1.5.3
    runtime    : 1.5.3

The problem I am presenting is that Ghostty is using 100% of each processor with every tab open, with each new tab, the CPU usage spikes to 100% for that additional core.
In the screenshots I am attaching, you can see what I am explaining, each new tab shows an increase in CPU usage. That reddish color indicates background usage, and most apps that monitor CPU usage, like htop or btop, do not detect this type of background usage. That plugin is the System monitor applet from Cinnamon.

I am using Manjaro Linux, and I am attaching the relevant info from sudo inxi -Fazy here:

System:
  Kernel: 5.15.165-1-MANJARO arch: x86_64 bits: 64 compiler: gcc v: 14.2.1
    clocksource: tsc avail: hpet,acpi_pm
    parameters: BOOT_IMAGE=/@/boot/vmlinuz-5.15-x86_64
    root=UUID=a9cbf476-db13-43bc-a095-49aa2591e826 rw rootflags=subvol=@ quiet
    udev.log_priority=3
  Desktop: Cinnamon v: 6.2.9 tk: GTK v: 3.24.43 wm: Muffin v: 6.2.0 tools:
    avail: cinnamon-screensaver dm: LightDM v: 1.32.0 Distro: Manjaro
    base: Arch Linux
CPU:
  Info: model: Intel Core i7-6700HQ socket: U3E1 bits: 64 type: MT MCP
    arch: Skylake-S gen: core 6 level: v3 note: check built: 2015
    process: Intel 14nm family: 6 model-id: 0x5E (94) stepping: 3
    microcode: 0xF0
  Topology: cpus: 1x dies: 1 cores: 4 threads: 8 tpc: 2 smt: enabled cache:
    L1: 256 KiB desc: d-4x32 KiB; i-4x32 KiB L2: 1024 KiB desc: 4x256 KiB
    L3: 6 MiB desc: 1x6 MiB
  Speed (MHz): avg: 2705 min/max: 800/3500 base/boost: 3100/8300 scaling:
    driver: intel_pstate governor: powersave volts: 1.1 V ext-clock: 100 MHz
    cores: 1: 2705 2: 2705 3: 2705 4: 2705 5: 2705 6: 2705 7: 2705 8: 2705
    bogomips: 41621
  Flags: avx avx2 ht lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx
  Vulnerabilities:
  Type: gather_data_sampling status: Vulnerable: No microcode
  Type: itlb_multihit status: KVM: VMX disabled
  Type: l1tf mitigation: PTE Inversion; VMX: conditional cache flushes, SMT
    vulnerable
  Type: mds mitigation: Clear CPU buffers; SMT vulnerable
  Type: meltdown mitigation: PTI
  Type: mmio_stale_data mitigation: Clear CPU buffers; SMT vulnerable
  Type: reg_file_data_sampling status: Not affected
  Type: retbleed mitigation: IBRS
  Type: spec_rstack_overflow status: Not affected
  Type: spec_store_bypass mitigation: Speculative Store Bypass disabled via
    prctl and seccomp
  Type: spectre_v1 mitigation: usercopy/swapgs barriers and __user pointer
    sanitization
  Type: spectre_v2 mitigation: IBRS; IBPB: conditional; STIBP: conditional;
    RSB filling; PBRSB-eIBRS: Not affected; BHI: Not affected
  Type: srbds mitigation: Microcode
  Type: tsx_async_abort mitigation: TSX disabled
Graphics:
  Device-1: Intel HD Graphics 530 vendor: CLEVO/KAPOK driver: i915 v: kernel
    arch: Gen-9 process: Intel 14n built: 2015-16 ports: active: eDP-1
    empty: none bus-ID: 00:02.0 chip-ID: 8086:191b class-ID: 0300
  Device-2: NVIDIA GM107M [GeForce GTX 960M] vendor: CLEVO/KAPOK
    driver: nvidia v: 550.107.02 alternate: nouveau,nvidia_drm non-free: 550.xx+
    status: current (as of 2024-09; EOL~2026-12-xx) arch: Maxwell code: GMxxx
    process: TSMC 28nm built: 2014-2019 pcie: gen: 2 speed: 5 GT/s lanes: 8
    link-max: gen: 3 speed: 8 GT/s lanes: 16 ports: active: none
    empty: DP-1,DP-2,HDMI-A-1 bus-ID: 01:00.0 chip-ID: 10de:139b class-ID: 0300
  Display: x11 server: X.org v: 1.21.1.13 with: Xwayland v: 24.1.2 driver: X:
    loaded: modesetting,nvidia gpu: i915 display-ID: :0 screens: 1
  Screen-1: 0 s-res: 1920x1080 s-size: <missing: xdpyinfo>
  Monitor-1: eDP-1 mapped: eDP-1-1 model: LG Display 0x046f built: 2014
    res: 1920x1080 hz: 60 dpi: 142 gamma: 1.2 size: 344x194mm (13.54x7.64")
    diag: 395mm (15.5") ratio: 16:9 modes: 1920x1080
  API: EGL v: 1.5 hw: drv: intel iris drv: nvidia platforms: device: 0
    drv: nvidia device: 2 drv: iris device: 3 drv: swrast gbm: drv: nvidia
    surfaceless: drv: nvidia x11: drv: nvidia inactive: wayland,device-1
  API: OpenGL v: 4.6.0 compat-v: 4.5 vendor: nvidia mesa v: 550.107.02
    glx-v: 1.4 direct-render: yes renderer: NVIDIA GeForce GTX 960M/PCIe/SSE2
    memory: 1.95 GiB
  API: Vulkan v: 1.3.279 layers: 1 device: 0 type: discrete-gpu
    name: NVIDIA GeForce GTX 960M driver: nvidia v: 550.107.02
    device-ID: 10de:139b surfaces: xcb,xlib device: 1 type: integrated-gpu
    name: Intel HD Graphics 530 (SKL GT2) driver: mesa intel v: 24.1.6-arch1.1
    device-ID: 8086:191b surfaces: xcb,xlib
Swap:
  Kernel: swappiness: 60 (default) cache-pressure: 100 (default) zswap: yes
    compressor: zstd max-pool: 20%
  ID-1: swap-1 type: file size: 512 MiB used: 488.4 MiB (95.4%) priority: -2
    file: /swap/swapfile
Info:
  Memory: total: 32 GiB available: 31.16 GiB used: 11.78 GiB (37.8%)
    igpu: 128 MiB
  Processes: 457 Power: uptime: 114d 12h 35m states: freeze,mem,disk
    suspend: deep avail: s2idle wakeups: 258 fails: 2 hibernate: platform
    avail: shutdown, reboot, suspend, test_resume image: 12.46 GiB
    services: csd-power,upowerd Init: systemd v: 256 default: graphical
    tool: systemctl

Here are the screenshots:

[rhodes-b]

I dont think tabs are supposed to get too many unique resources but can you try setting
gtk-single-instance = true in your config
https://ghostty.org/docs/help/gtk-single-instance
has some more info on what it does

[00-kat]

That's probably irrelevant.

[plinkr]

I changed the setting as you recommended, but the behavior is still the same

[00-kat]

Maybe it's related to #3224.

[plinkr]

They may be related, the slowness described in that discussion is also something I see here on Manjaro

[philippehenin]

Just wanted to help. I have been using ghostty on different linux laptops for a few days. It is nice and works flawlessly.

On my chromebook (debian 12), I have the high CPU problem. I have tried the .deb install the v1.0.1 and v1.0.0 build from sources. I see the strange behavior.

I did a small screencast to illustrate https://screencast.apps.chrome/1-MjA6K6nhMgpyFAp0fFtp8G53kCfBO3g?createdTime=2025-01-03T12%3A51%3A08.447Z

I hope it helps. It looks like software rendering vs. hardware video rendering, still searching…

I applied the "Epol" proposal, it is way better. But I am still a bit concern. For me, it is still doing too much cpu. But it is useable now.

https://screencast.apps.chrome/1-cd5ZeBq7WBnYo4rv12abaG-3rLmchfl?createdTime=2025-01-03T13%3A48%3A30.253Z

Compare to a "native" debian 12 (on old slower laptop) with normal cpu usage: https://youtu.be/i0-Jh3BXbMg.

P.

[plinkr]

In the second screencast you show, the ghostty you have in your Gits/ghostty folder is indeed compiled with the fixes using epoll instead of io_uring, but you are running the ghostty that is in your $PATH, which still has the backend using io_uring, and that's why it continues to show elevated iowait usage. Use the ghostty compiled with the changes, located at: ~/Gits/ghostty/zig-out/bin/ghostty.

In the screencast at the 0:40 second mark when starting ghostty, you can see that the backend is still set to io_uring and not epoll as it should be with the fix.

When starting ghostty, the console should display this:

$ zig-out/bin/ghostty 
info: ghostty version=1.0.2-dev+0000000
info: ghostty build optimize=ReleaseFast
info: runtime=apprt.Runtime.gtk
info: font_backend=font.main.Backend.fontconfig_freetype
info: dependency harfbuzz=8.4.0
info: dependency fontconfig=21402
info: renderer=renderer.OpenGL
info: libxev backend=main.Backend.epoll

take special notice to the line info: libxev backend=main.Backend.epoll

[philippehenin]

Effectively, my bad for the command.

No problem anymore. CPU normal with the correct executable.

philippehenin@penguin:~$ Gits/ghostty/zig-out/bin/ghostty 
info: ghostty version=1.0.1
info: ghostty build optimize=ReleaseFast
info: runtime=apprt.Runtime.gtk
info: font_backend=font.main.Backend.fontconfig_freetype
info: dependency harfbuzz=8.4.0
info: dependency fontconfig=21402
info: renderer=renderer.OpenGL
**info: libxev backend=main.Backend.epoll**
info(os): setlocale from env result=en_US.UTF-8
info(gtk): GTK version build=4.8.3 runtime=4.8.3
info: reading configuration file path=/home/philippehenin/.config/ghostty/config
info(config): default shell source=env value=/bin/bash
info(sentry): sentry envelope does not contain crash, discarding
info(gtk): libadwaita version build=1.2.2 runtime=1.2.2

Thank you for the great reply and the great terminal.
P.

[gzhechu]

I meet same situation in my openSUSE slowroll. I am using opensuse-slowroll with most recent update, KDE destop environment. I installed ghostty from prebuild binary for openSUSE following this instruction: https://ghostty.org/docs/install/binary#opensuse, and I noticed when I start ghostty, the CPU monitor applet shows servel high CPU usage, when I add a new tab, the CPU bar in applet synchronization increased. After I quit ghostty, the CPU bar resumed to normal.

robin@k8plus:~> cat /etc/os-release
NAME="openSUSE Tumbleweed-Slowroll"

VERSION="20250101"

ID="opensuse-slowroll"
ID_LIKE="opensuse-tumbleweed opensuse suse"
VERSION_ID="20250101"
PRETTY_NAME="openSUSE Tumbleweed-Slowroll"
ANSI_COLOR="0;32"

CPE 2.3 format, boo#1217921

CPE_NAME="cpe:2.3:o:opensuse:slowroll:20250101:::::::*"
#CPE 2.2 format
#CPE_NAME="cpe:/o:opensuse:slowroll:20250101"
BUG_REPORT_URL="https://bugzilla.opensuse.org"
SUPPORT_URL="https://bugs.opensuse.org"
HOME_URL="https://www.opensuse.org"
DOCUMENTATION_URL="https://en.opensuse.org/openSUSE:Slowroll"
LOGO="distributor-logo-Slowroll"

robin@k8plus:~> ghostty --version
Ghostty 1.0.1

Version

• version: 1.0.1
• channel: stable
  Build Config
• Zig version: 0.13.0
• build mode : builtin.OptimizeMode.ReleaseFast
• app runtime: apprt.Runtime.gtk
• font engine: font.main.Backend.fontconfig_freetype
• renderer : renderer.OpenGL
• libxev : main.Backend.io_uring
• GTK version:
  build : 4.16.12
  runtime : 4.16.7
• libadwaita : enabled
  build : 1.6.3
  runtime : 1.6.2
• libX11 : enabled
  robin@k8plus:~>

[plinkr]

Please read this post: #3224. It describes the reason for this problem, and one solution is to recompile ghostty by following the steps in this comment: #3224 (reply in thread)