Zsh Speedup

I’ve been experiencing some slowdowns in my shell lately, I could not explain why. But I am using Oh My Zsh, and after some searching I found a blog post by Matthew J. Clemente that has a complete walkthrough of how to diagnose and fix slow (Oh My Zsh) shells.

You start by measuring actual load times to set a base with a simple function you can put into your .zshrc file:

bash


timezsh() {
  shell=${1-$SHELL}
  for i in $(seq 1 10); do /usr/bin/time $shell -i -c exit; done
}

Now you can run timezsh and see how long it takes for your shell to start up and be ready. To figure out exactly which plugin is causing the slowdown you can run the following to see how long it takes for each plugin to be loaded in:

bash


# Load all of the plugins that were defined in ~/.zshrc  
for plugin ($plugins); do
  timer=$(($(gdate +%s%N)/1000000))
  if [ -f $ZSH_CUSTOM/plugins/$plugin/$plugin.plugin.zsh ]; then  
    source $ZSH_CUSTOM/plugins/$plugin/$plugin.plugin.zsh  
  elif [ -f $ZSH/plugins/$plugin/$plugin.plugin.zsh ]; then  
    source $ZSH/plugins/$plugin/$plugin.plugin.zsh  
  fi  
  now=$(($(gdate +%s%N)/1000000))
  elapsed=$(($now-$timer))  
  echo $elapsed":" $plugin  
done

In my case it was the kubectl plugin for Oh My Zsh, the fix was to use the given kubectl command to load in the autocomplete:

bash


function kubectl() {
    if ! type __start_kubectl >/dev/null 2>&1; then
        source <(command kubectl completion zsh)
    fi

    command kubectl "$@"
}

Now I can remove the plugin and lazy load the kubectl command every time I start up a new shell session.

Sometimes you don’t need a plugin for things, take each plugin you install seriously and check if you really need it. A slow shell is not great and a killer for productivity.

Source: https://blog.mattclemente.com/2020/06/26/oh-my-zsh-slow-to-load.html