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Fix Slow Shell ZSH

July 02, 2024

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.


I’m a Software Engineer passionate about solving problems and pushing tech boundaries. I love reading, listening/playing music, appreciating/making art, and enjoying a good cup of coffee. I hope you enjoy reading my essays.

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