A fast, lightweight and minimalistic Wayland terminal emulator
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4.1 KiB



All benchmarks are done using vtebench:

vtebench -h $(tput lines) -w $(tput cols) -b 104857600 alt-screen-random-write > ~/alt-random
vtebench -c -h $(tput lines) -w $(tput cols) -b 104857600 alt-screen-random-write > ~/alt-random-colors
vtebench -h $(tput lines) -w $(tput cols) -b 10485760 scrolling > ~/scrolling
vtebench -h $(tput lines) -w $(tput cols) -b 104857600 scrolling --fill-lines > ~/scrolling-filled-lines
vtebench -h $(tput lines) -w $(tput cols) -b 10485760 unicode-random-write > ~/unicode-random

They were "executed" using benchmark.py, which will load each file into memory, and then print it to the terminal. This is done 20 times for each test. Then it calculates the mean and standard deviation for each test.



CPU: i9-9900


Graphics: Radeon RX 5500XT

Terminal configuration

Geometry: 2040x1884

Font: Fantasque Sans Mono 10.00pt/23px

Scrollback: 10000 lines


Benchmark Foot (GCC+PGO) 1.7.0.r2 Foot 1.7.0.r2 Alacritty 0.7.2 URxvt 9.22 XTerm 366
alt-random 0.382s ±0.003 0.550s ±0.007 0.995s ±0.010 1.201s ±0.006 12.756s ±0.045
alt-random-colors 0.380s ±0.002 0.543s ±0.003 1.017s ±0.013 1.399s ±0.018 11.591s ±0.141
scrolling 1.302s ±0.019 1.284s ±0.052 1.107s ±0.028 1.097s ±0.015 37.537s ±0.121
scrolling-filled-lines 0.646s ±0.016 0.610s ±0.003 1.290s ±0.012 1.325s ±0.037 6.817s ±0.084
unicode-random 0.167s ±0.001 0.276s ±0.445 0.097s ±0.002 1 18.032s ±0.334 29.731s ±3.746



CPU: i5-8250U


Graphics: Intel UHD Graphics 620

Terminal configuration

Geometry: 945x1020

Font: Dina:pixelsize=12

Scrollback=10000 lines


Benchmark Foot (GCC+PGO) 1.7.0.r2 Foot (no PGO) 1.7.0.r2 Alacritty 0.7.2 URxvt 9.22 St 0.8.4 XTerm 366
alt-random 0.714s ±0.047 0.900s ±0.041 1.586s ±0.045 1.684s ±0.034 2.054s ±0.121 37.205s ±0.252
alt-random-colors 0.736s ±0.054 0.950s ±0.082 1.565s ±0.043 2.150s ±0.137 2.195s ±0.154 33.112s ±0.167
scrolling 1.593s ±0.070 1.559s ±0.055 1.517s ±0.079 1.462s ±0.052 3.308s ±0.133 134.432s ±0.436
scrolling-filled-lines 1.178s ±0.044 1.309s ±0.045 2.281s ±0.086 2.044s ±0.060 2.732s ±0.056 20.753s ±0.067
unicode-random 0.349s ±0.009 0.352s ±0.007 0.148s ±0.010 1 19.090s ±0.363 crashed 15.579s ±0.093

Alacritty and "unicode-random"

Alacritty is actually really slow at rendering this (whether it is fallback fonts in general, emojis, or something else, I don't know).

I believe the reason it finishes the benchmark so quickly is because it reads from the PTY in a separate thread, into a larger receive buffer which is then consumed by the main thread. This allows the client program to write its output much faster since it is no longer stalling on a blocked PTY.

This means Alacritty only needs to render a couple of frames since it can reach the final VT state almost immediately.

On the other hand, cat:ing the unicode-random test file in an endless loop, or just manually scrolling up after the benchmark is done is slow, which besides being felt (input lag), can be seen by setting debug.render_timer = true in alacritty.yml.