2024-07-31/02: add "Troubleshoting: terminal lag and solutions with N…

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2024-07-31/.02-troubleshooting-terminal-lag-and-solutions-with-nix.md

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+# Troubleshoting: terminal lag and solutions with Nix
+
+Inspired by this [blog post from
+Tavis](https://lock.cmpxchg8b.com/slowterm.html), I decided to document my own
+recent journey of reducing terminal lag startup. This post is way less
+interesting than the one from Tavis that uses a debugger to patch applications
+on the fly, but should still be interesting for some. And it also shows how
+powerful Nix can be for some things.
+
+For context, I have basically 3 systems where I interact with terminal
+frequently:
+
+- Thinkpad P14s Gen 1 running NixOS, with a reasonable fast CPU and disk
+- [MacBook Pro "M1
+  Pro"](https://everymac.com/systems/apple/macbook_pro/specs/macbook-pro-m1-pro-10-core-cpu-16-core-gpu-16-2021-specs.html)
+  (what an awful name scheme Apple) with a really fast CPU and disk, but of
+  course running macOS
+  + Sadly this is being phased-out since this is a job owned machine and I am
+    changing jobs right now, but will be replaced with another one soon™
+- [Chromebook Duet
+  3](https://chromeunboxed.com/lenovo-chromebook-duet-3-review-perfect-sequel)
+  running ChromeOS, with slow CPU and disk
+
+My experience is similar to Tavis, at around 300ms of startup time I don't care
+too much, but around 500ms+ is where I start to notice. I never had any issues
+with startup time in NixOS itself (I had issues with macOS before, but it was
+not actually the fault of macOS), but in the Chromebook it was awful: 600ms+
+with [hot
+start](https://www.instabug.com/blog/understanding-cold-hot-and-warm-app-launch-time),
+while cold start it could be multiple seconds.
+
+The shell that I used is ZSH, and we check how long it takes to start by using:
+
+```
+$ time zsh -ci exit
+zsh -ic exit  0.04s user 0.10s system 100% cpu 0.143 total
+```
+
+The `-i` flag here is important, because we are interested in the interactive
+use of ZSH. Without this flag ZSH will ignore your `~/.zshrc` file, and the
+results will be meaningless.
+
+To do a more interesting benchmark, we can use [`hyperfine`](https://github.com/sharkdp/hyperfine):
+
+```
+$ hyperfine "zsh -ic exit"
+Benchmark 1: zsh -ic exit
+  Time (mean ± σ):     145.4 ms ±   4.2 ms    [User: 49.8 ms, System: 97.3 ms]
+  Range (min … max):   138.6 ms … 155.3 ms    19 runs
+```
+
+Hyperfine will run the command multiple times and take care of things like
+shell startup time. A really great tool to have in your toolbox by the way, but
+I digress.