[jhchabran]

The delay in between typing and seeing it rendered, drawing large portions of text (which matters if you spend a lot of time in term based editors) etc ...

It's very subjective: some folks (me included) will notice the difference and feel frustrated if it's not fast enough, while others are scratching their head about how it actually makes a difference.

It could also be said, that it's of logical to expect certain things to be fast; especially when they've been around for so long. We're drawing text on the screen here, it should be fast.

Saying it matters with anything else than feeling/comfort would be overreaching.

[saurik]

The issue is that usually these terminals mean "higher throughput" when they say "faster", not "lower latency". The lowest-latency terminal in every test is Xterm, often by a LOT. Alacritty for a long time was actually quite bad at latency--and notably had a high variance on its latency, which is particularly miserable--but I think it improved recently? From what I remember of these benchmarks, someone using urxvt isn't going to be impressed by the supposed speed of Alacritty, if we are talking latency (and I agree: we should be, and everyone should use Xterm, which is actually an insanely good terminal).

As for throughput, I have lived in the terminal for decades, and as long as the various layers don't have massive buffers I honestly don't care how slow the terminal is: if I am dumping megabytes into my terminal backscroll I probably am going "oh shit" and am frantically hitting Ctrl-C... a slow terminal with a small buffer handles that almost immediately. I get the impression that there are maybe some use cases involving high-rate screen updates for apps that happen to run in consoles but are really GUIs... I don't use many of those and in fact try to avoid them, but I could maybe see an advantage for a high-throughput terminal to improve their simulated frame rate?

[GuB-42]

People writing fast terminal emulator care about throughput, latency and resource utilization. Kitty for instance deliberately limit throughput to keep both latency and CPU/GPU usage reasonable.

Also, by what metric is xterm so fast? I accept the idea that it is fast, even the fastest, but "a lot" seems suspicious to me. From the keyboard to the monitor, there is a lot of hardware and driver latency, I guess tens of milliseconds, so the effect of the terminal, should be relatively minor. I suspect xterm is so fast because the tool used to test it relies on the X server, and because xterm communicates with X directly, the latency will be really low from the point of view of X, but how is it end-to-end? Do we get the same results, with, say, Wayland?

[eviks]

here is some latency tests using an external camera, though that's Windows only, there might've been a similar one for Linux, but not sure

https://chadaustin.me/2024/02/windows-terminal-latency/

The other one where xterm is uber low is https://lwn.net/Articles/751763/ is using this tool with software-based screen capture https://pavelfatin.com/typometer/, not sure how reliable that is as a proxy for end-to-end (at the time of the benchmark Wayland wasn't supported)