3 ms·

I used to be a NetHack speedrunner. Pressing the keys real fast. All of it in terminals. I had the fastest run for almost 10 years. Input lag was a thing I thou

by adeon 2y ago

I used to be a NetHack speedrunner. Pressing the keys real fast. All of it in terminals. I had the fastest run for almost 10 years. Input lag was a thing I thought sometimes. Everything below is based on pure gut feelings because I never measured any of it. I've long wondered why some terminals and operating systems felt like they were pretty laggy. In the sense that if I press my character to move, how long until they actually move? iTerm2 on MacOS is worst offender. But I can't tell if it's iTerm2 or MacOS itself. I remember trying other terminals on Mac, and it was mostly the same. iTerm2 itself also had bunch of rendering options, but I couldn't get them to do anything I could actually feel affected input lag. One thought I had was: maybe iTerm2 added 1 frame lateness, and MacOS itself added another? But that would be ~30ms on a 60fps monitor which I can easily already tell on a server-connection NetHack. I also have no idea if measuring "N frames late" is actually a sensible way to think about this. I assume computers know when a key is pressed at a higher frequency? Linux xterm and rxvt were the fastest that I remember, on X11 (I've never used Wayland like in the article, well not for NetHack anyway). I have no idea how compositors work on any of these operating systems or X11/Wayland to say anything smart about them or why they would be slower or faster. Reading the article...I realized I have that same iPhone 15 Pro with 240fps recording. I could replicate that experiment, but testing out terminals on various operating systems instead I used to play on. So I could now test if my gut feeling was right all along or not. or maybe it lied to me all these years. I wrote the idea in the article down on my notes, maybe when I'm bored enough I'll try it :) and I can stop saying propaganda about iTerm2 being slow if it turns out I was completely wrong. Maybe I have easier time because all my NetHack days were 60fps, so I have more leeway in measurements. I'm not active in NetHack playing anymore, although I sometimes play it as a comfort game.

patal 2y ago
iTerm2 is on 45ms and more in this measuring: https://danluu.com/term-latency/ https://danluu.com/term-latency/ There, it's distinct in that other terminals have lower latency on the same system.
- adeon 2y ago
  Ooh that is interesting. Also noticed this passage: "When people measure actual end-to-end latency for games on normal computer setups, they usually find latencies in the 100ms range." That is really surprising to me. 100ms is HUGE. On NetHack, sshing into servers the difference between 50ms and 150ms is enormous. If do my experiment and I'm not too lazy I want to check on that 100ms figure, your link points to more sources which I didn't check on right now. I don't know if I'm blind but I can't tell when that article was written exactly. But it mentioned MacBook 2014 and Lubuntu 16.04 so maybe it's around mid 2010, 2016 possibly? (I should check properly if I do my experiments) The author in the Wayland vs X11 used mouse flicks on the video. Just now while writing I kind of had a thought if this needs some more deep thinking: how do I accurately measure "my finger touched this button and X milliseconds later character moved". Wondering what to consider as the "finger touched this button" event in a 240fps video. Maybe I can do what the author did and map a key to a mouse instead, because maybe there's a much-easier-to-see physical movement with a mouse. But then, am I really measuring faithfully my old NetHack-like environment? Or maybe this isn't really an issue and it'll be easy to tell. Too much for my small brain to think in the moment :) that link gave me at least some validation that iTerm2 maybe really is a bit slow, or at least was at that time. There's also bunch of terminals on that page I've never heard of. Today iTerm2 is my daily driver, but xterm is still really fast on my Fedora Linux system I have on the side.

by adeon 2y ago

patal 2y ago

iTerm2 is on 45ms and more in this measuring: https://danluu.com/term-latency/ https://danluu.com/term-latency/ There, it's distinct in that other terminals have lower latency on the same system.

adeon 2y ago
Ooh that is interesting. Also noticed this passage: "When people measure actual end-to-end latency for games on normal computer setups, they usually find latencies in the 100ms range." That is really surprising to me. 100ms is HUGE. On NetHack, sshing into servers the difference between 50ms and 150ms is enormous. If do my experiment and I'm not too lazy I want to check on that 100ms figure, your link points to more sources which I didn't check on right now. I don't know if I'm blind but I can't tell when that article was written exactly. But it mentioned MacBook 2014 and Lubuntu 16.04 so maybe it's around mid 2010, 2016 possibly? (I should check properly if I do my experiments) The author in the Wayland vs X11 used mouse flicks on the video. Just now while writing I kind of had a thought if this needs some more deep thinking: how do I accurately measure "my finger touched this button and X milliseconds later character moved". Wondering what to consider as the "finger touched this button" event in a 240fps video. Maybe I can do what the author did and map a key to a mouse instead, because maybe there's a much-easier-to-see physical movement with a mouse. But then, am I really measuring faithfully my old NetHack-like environment? Or maybe this isn't really an issue and it'll be easy to tell. Too much for my small brain to think in the moment :) that link gave me at least some validation that iTerm2 maybe really is a bit slow, or at least was at that time. There's also bunch of terminals on that page I've never heard of. Today iTerm2 is my daily driver, but xterm is still really fast on my Fedora Linux system I have on the side.