I made this: https://github.com/romkatv/zsh-bench Summary: - `zsh-bench` measures user-visible latency of interactive zsh: *input lag*, *command lag*, etc. You can use it to benchmark your own shell. - `human-bench` measures human perception of latency when using interactive zsh. You can use it to check how it feels to use zsh with specific latencies or to test whether you can tell a difference between 5ms and 0ms lag. - I've used `human-bench` to conduct a blind study on myself to find the maximum values of latencies that are indistinguishable from zero. For example, *command lag* below 10ms feels just like 0ms but anything above this value starts feeling sluggish. - I've used these threshold values to normalize benchmark results to see what is fast and what is slow. - Armed with this set of tools I've optimized two of my zsh projects: powerlevel10k and zsh4humans. They used to be fairly fast but now they are literally indistinguishable from instantaneous as far as human perception goes. - I've benchmarked many zsh techniques, plugins, frameworks and plugin managers and have shared my observations in the document together with a brief conclusion. This is unlikely to be of practical use to many here but hopefully will prove entertaining to a few. Roman.