Fix Slow Shell ZSH

Lately, my shell (zsh) feels slow to use. Even booting it for the first time feels like it is slow to render. It shouldn’t happen as I am using a beefy MacBook Pro. I also don’t don’t use any other zsh plugin other than git. So, I decided to investigate what is causing the slowness.

A quick search on the internet led me to the zsh profiling feature. I can profile the shell using this:

Put the following code at the start and end of your .zshrc file:

zmodload zsh/zprof # your zshrc file content here. zprof

Save it and source the ~/.zshrc file. Now, you can see the profiling output by running zprof.

num calls time self name ----------------------------------------------------------------------------------- 1) 1 3886.43 3886.43 93.04% 3348.16 3348.16 80.15% compinit 2) 831 381.00 0.46 9.12% 381.00 0.46 9.12% compdef 3) 2 169.68 84.84 4.06% 98.30 49.15 2.35% nvm 4) 1 86.15 86.15 2.06% 86.15 86.15 2.06% compdump 5) 2 71.57 35.78 1.71% 71.57 35.78 1.71% compaudit 6) 22 77.67 3.53 1.86% 58.00 2.64 1.39% _omz_source 7) 1 62.61 62.61 1.50% 54.07 54.07 1.29% nvm_ensure_version_installed 8) 1 209.63 209.63 5.02% 39.95 39.95 0.96% nvm_auto 9) 1 8.54 8.54 0.20% 8.54 8.54 0.20% nvm_is_version_installed 10) 1 8.33 8.33 0.20% 8.02 8.02 0.19% nvm_die_on_prefix 11) 1 6.24 6.24 0.15% 6.24 6.24 0.15% regexp-replace 12) 4 3.69 0.92 0.09% 3.69 0.92 0.09% add-zsh-hook 13) 1 3.62 3.62 0.09% 3.62 3.62 0.09% colors 14) 6 3.57 0.59 0.09% 3.57 0.59 0.09% is-at-least 15) 1 2.99 2.99 0.07% 2.99 2.99 0.07% zrecompile 16) 1 2.12 2.12 0.05% 2.12 2.12 0.05% test-ls-args 17) 1 0.44 0.44 0.01% 0.44 0.44 0.01% nvm_has 18) 2 0.31 0.16 0.01% 0.31 0.16 0.01% is_plugin 19) 4 0.31 0.08 0.01% 0.31 0.08 0.01% nvm_npmrc_bad_news_bears 20) 1 0.08 0.08 0.00% 0.04 0.04 0.00% complete 21) 3 0.04 0.01 0.00% 0.04 0.01 0.00% is_theme 22) 2 0.02 0.01 0.00% 0.02 0.01 0.00% bashcompinit 23) 2 0.02 0.01 0.00% 0.02 0.01 0.00% env_default 24) 1 209.65 209.65 5.02% 0.02 0.02 0.00% nvm_process_parameters 25) 1 0.01 0.01 0.00% 0.01 0.01 0.00% nvm_is_zsh ----------------------------------------------------------------------------------- 1) 1 3886.43 3886.43 93.04% 3348.16 3348.16 80.15% compinit 1/2 71.57 71.57 1.71% 0.28 0.28 compaudit [5] 1/1 86.15 86.15 2.06% 86.15 86.15 compdump [4] 818/831 380.55 0.47 9.11% 380.55 0.47 compdef [2] ----------------------------------------------------------------------------------- 818/831 380.55 0.47 9.11% 380.55 0.47 compinit [1] 12/831 0.41 0.03 0.01% 0.41 0.03 _omz_source [6] 1/831 0.04 0.04 0.00% 0.04 0.04 complete [20] 2) 831 381.00 0.46 9.12% 381.00 0.46 9.12% compdef ----------------------------------------------------------------------------------- 24) 1 209.65 209.65 5.02% 0.02 0.02 0.00% nvm_process_parameters 1/1 209.63 209.63 5.02% 39.95 39.95 nvm_auto [8] ----------------------------------------------------------------------------------- 1/1 209.63 209.63 5.02% 39.95 39.95 nvm_process_parameters [24] 8) 1 209.63 209.63 5.02% 39.95 39.95 0.96% nvm_auto 1/2 169.68 169.68 4.06% 4.92 4.92 nvm [3] ----------------------------------------------------------------------------------- 1/2 169.68 169.68 4.06% 4.92 4.92 nvm_auto [8] 1/2 164.76 164.76 3.94% 93.38 93.38 nvm [3] 3) 2 169.68 84.84 4.06% 98.30 49.15 2.35% nvm 1/1 0.44 0.44 0.01% 0.44 0.44 nvm_has [17] 1/1 8.33 8.33 0.20% 8.02 8.02 nvm_die_on_prefix [10] 1/1 62.61 62.61 1.50% 54.07 54.07 nvm_ensure_version_installed [7] 1/2 164.76 164.76 3.94% 93.38 93.38 nvm [3] ----------------------------------------------------------------------------------- 1/1 86.15 86.15 2.06% 86.15 86.15 compinit [1] 4) 1 86.15 86.15 2.06% 86.15 86.15 2.06% compdump ----------------------------------------------------------------------------------- 6) 22 77.67 3.53 1.86% 58.00 2.64 1.39% _omz_source 1/2 0.01 0.01 0.00% 0.01 0.01 bashcompinit [22] 2/2 0.02 0.01 0.00% 0.02 0.01 env_default [23] 12/831 0.41 0.03 0.01% 0.41 0.03 compdef [2] 1/1 2.12 2.12 0.05% 2.12 2.12 test-ls-args [16] 6/6 3.57 0.59 0.09% 3.57 0.59 is-at-least [14] 1/1 3.62 3.62 0.09% 3.62 3.62 colors [13] 4/4 3.69 0.92 0.09% 3.69 0.92 add-zsh-hook [12] 1/1 6.24 6.24 0.15% 6.24 6.24 regexp-replace [11] ----------------------------------------------------------------------------------- 1/2 71.57 71.57 1.71% 0.28 0.28 compinit [1] 1/2 71.29 71.29 1.71% 71.29 71.29 compaudit [5] 5) 2 71.57 35.78 1.71% 71.57 35.78 1.71% compaudit 1/2 71.29 71.29 1.71% 71.29 71.29 compaudit [5] ----------------------------------------------------------------------------------- 1/1 62.61 62.61 1.50% 54.07 54.07 nvm [3] 7) 1 62.61 62.61 1.50% 54.07 54.07 1.29% nvm_ensure_version_installed 1/1 8.54 8.54 0.20% 8.54 8.54 nvm_is_version_installed [9] ----------------------------------------------------------------------------------- 1/1 8.54 8.54 0.20% 8.54 8.54 nvm_ensure_version_installed [7] 9) 1 8.54 8.54 0.20% 8.54 8.54 0.20% nvm_is_version_installed ----------------------------------------------------------------------------------- 1/1 8.33 8.33 0.20% 8.02 8.02 nvm [3] 10) 1 8.33 8.33 0.20% 8.02 8.02 0.19% nvm_die_on_prefix 4/4 0.31 0.08 0.01% 0.31 0.08 nvm_npmrc_bad_news_bears [19] ----------------------------------------------------------------------------------- 1/1 6.24 6.24 0.15% 6.24 6.24 _omz_source [6] 11) 1 6.24 6.24 0.15% 6.24 6.24 0.15% regexp-replace ----------------------------------------------------------------------------------- 4/4 3.69 0.92 0.09% 3.69 0.92 _omz_source [6] 12) 4 3.69 0.92 0.09% 3.69 0.92 0.09% add-zsh-hook ----------------------------------------------------------------------------------- 1/1 3.62 3.62 0.09% 3.62 3.62 _omz_source [6] 13) 1 3.62 3.62 0.09% 3.62 3.62 0.09% colors ----------------------------------------------------------------------------------- 6/6 3.57 0.59 0.09% 3.57 0.59 _omz_source [6] 14) 6 3.57 0.59 0.09% 3.57 0.59 0.09% is-at-least ----------------------------------------------------------------------------------- 15) 1 2.99 2.99 0.07% 2.99 2.99 0.07% zrecompile ----------------------------------------------------------------------------------- 1/1 2.12 2.12 0.05% 2.12 2.12 _omz_source [6] 16) 1 2.12 2.12 0.05% 2.12 2.12 0.05% test-ls-args ----------------------------------------------------------------------------------- 1/1 0.44 0.44 0.01% 0.44 0.44 nvm [3] 17) 1 0.44 0.44 0.01% 0.44 0.44 0.01% nvm_has ----------------------------------------------------------------------------------- 18) 2 0.31 0.16 0.01% 0.31 0.16 0.01% is_plugin ----------------------------------------------------------------------------------- 4/4 0.31 0.08 0.01% 0.31 0.08 nvm_die_on_prefix [10] 19) 4 0.31 0.08 0.01% 0.31 0.08 0.01% nvm_npmrc_bad_news_bears ----------------------------------------------------------------------------------- 20) 1 0.08 0.08 0.00% 0.04 0.04 0.00% complete 1/831 0.04 0.04 0.00% 0.04 0.04 compdef [2] ----------------------------------------------------------------------------------- 21) 3 0.04 0.01 0.00% 0.04 0.01 0.00% is_theme ----------------------------------------------------------------------------------- 1/2 0.01 0.01 0.00% 0.01 0.01 _omz_source [6] 22) 2 0.02 0.01 0.00% 0.02 0.01 0.00% bashcompinit ----------------------------------------------------------------------------------- 2/2 0.02 0.01 0.00% 0.02 0.01 _omz_source [6] 23) 2 0.02 0.01 0.00% 0.02 0.01 0.00% env_default ----------------------------------------------------------------------------------- 25) 1 0.01 0.01 0.00% 0.01 0.01 0.00% nvm_is_zsh

If notice the output you would see the nvm showing prominently in it. It means it’s the reason for the slowness.

Here is my ~/.zshrc file for reference:

# If you come from bash you might have to change your $PATH. # export PATH=$HOME/bin:/usr/local/bin:$PATH # Path to your oh-my-zsh installation. export ZSH="$HOME/.oh-my-zsh" # Set name of the theme to load --- if set to "random", it will # load a random theme each time oh-my-zsh is loaded, in which case, # to know which specific one was loaded, run: echo $RANDOM_THEME # See https://github.com/ohmyzsh/ohmyzsh/wiki/Themes ZSH_THEME="robbyrussell" # Set list of themes to pick from when loading at random # Setting this variable when ZSH_THEME=random will cause zsh to load # a theme from this variable instead of looking in $ZSH/themes/ # If set to an empty array, this variable will have no effect. # ZSH_THEME_RANDOM_CANDIDATES=( "robbyrussell" "agnoster" ) # Uncomment the following line to use case-sensitive completion. # CASE_SENSITIVE="true" # Uncomment the following line to use hyphen-insensitive completion. # Case-sensitive completion must be off. _ and - will be interchangeable. # HYPHEN_INSENSITIVE="true" # Uncomment one of the following lines to change the auto-update behavior # zstyle ':omz:update' mode disabled # disable automatic updates # zstyle ':omz:update' mode auto # update automatically without asking # zstyle ':omz:update' mode reminder # just remind me to update when it's time # Uncomment the following line to change how often to auto-update (in days). # zstyle ':omz:update' frequency 13 # Uncomment the following line if pasting URLs and other text is messed up. # DISABLE_MAGIC_FUNCTIONS="true" # Uncomment the following line to disable colors in ls. # DISABLE_LS_COLORS="true" # Uncomment the following line to disable auto-setting terminal title. # DISABLE_AUTO_TITLE="true" # Uncomment the following line to enable command auto-correction. # ENABLE_CORRECTION="true" # Uncomment the following line to display red dots whilst waiting for completion. # You can also set it to another string to have that shown instead of the default red dots. # e.g. COMPLETION_WAITING_DOTS="%F{yellow}waiting...%f" # Caution: this setting can cause issues with multiline prompts in zsh < 5.7.1 (see #5765) # COMPLETION_WAITING_DOTS="true" # Uncomment the following line if you want to disable marking untracked files # under VCS as dirty. This makes repository status check for large repositories # much, much faster. # DISABLE_UNTRACKED_FILES_DIRTY="true" # Uncomment the following line if you want to change the command execution time # stamp shown in the history command output. # You can set one of the optional three formats: # "mm/dd/yyyy"|"dd.mm.yyyy"|"yyyy-mm-dd" # or set a custom format using the strftime function format specifications, # see 'man strftime' for details. # HIST_STAMPS="mm/dd/yyyy" # Would you like to use another custom folder than $ZSH/custom? # ZSH_CUSTOM=/path/to/new-custom-folder # Which plugins would you like to load? # Standard plugins can be found in $ZSH/plugins/ # Custom plugins may be added to $ZSH_CUSTOM/plugins/ # Example format: plugins=(rails git textmate ruby lighthouse) # Add wisely, as too many plugins slow down shell startup. plugins=(git) alias c='clear' alias activate='source venv/bin/activate' alias syncall='gco develop && ggpull && gco staging && ggpull && gco master && ggpull' alias vim="nvim" alias vi="nvim" alias v="nvim" source $ZSH/oh-my-zsh.sh # User configuration # export MANPATH="/usr/local/man:$MANPATH" # You may need to manually set your language environment # export LANG=en_US.UTF-8 # Preferred editor for local and remote sessions if [[ -n $SSH_CONNECTION ]]; then export EDITOR='vim' else export EDITOR='mvim' fi # Compilation flags # export ARCHFLAGS="-arch x86_64" # Set personal aliases, overriding those provided by oh-my-zsh libs, # plugins, and themes. Aliases can be placed here, though oh-my-zsh # users are encouraged to define aliases within the ZSH_CUSTOM folder. # For a full list of active aliases, run `alias`. # # Example aliases # alias zshconfig="mate ~/.zshrc" # alias ohmyzsh="mate ~/.oh-my-zsh" eval "$(zoxide init zsh)" . "$HOME/.cargo/env" export PATH="/opt/homebrew/opt/ruby/bin:$PATH" [ -f ~/.fzf.zsh ] && source ~/.fzf.zsh # export NVM_DIR="$HOME/.nvm" # [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh" # This loads nvm # [ -s "$NVM_DIR/bash_completion" ] && \. "$NVM_DIR/bash_completion" # This loads nvm bash_completion

Now, NVM is an useful tool, but it doesn’t need to be enabled all the time for my day to day development. So, I decided to just comment nvm for now and uncomment it as and when needed.

~Fin

Finally, my shell is back to normal speed. I hope this helps you too.