Improving ZSH startup performance
Adding profiling to ZSH
Add this line as the first one, to the very top of your ~/.zshrc:
zmodload zsh/zprof
And add this one to the very bottom of this same file:
zprof
Now, whenever you open up ZSH, you shall see a list of things which start and how much time each entry takes to load. For me it was like this:
num calls time self name
-----------------------------------------------------------------------------------
1) 1 1123.49 1123.49 87.59% 1123.49 1123.49 87.59% _pyenv-from-homebrew-installed
2) 1 84.02 84.02 6.55% 59.50 59.50 4.64% compinit
3) 3 26.94 8.98 2.10% 26.94 8.98 2.10% __sdkman_export_candidate_home
4) 3 25.77 8.59 2.01% 25.77 8.59 2.01% __sdkman_prepend_candidate_to_path
5) 2 24.52 12.26 1.91% 24.52 12.26 1.91% compaudit
6) 2 7.98 3.99 0.62% 7.98 3.99 0.62% grep-flag-available
7) 2 7.54 3.77 0.59% 7.54 3.77 0.59% env_default
8) 2 2.43 1.22 0.19% 2.43 1.22 0.19% _has
9) 23 2.43 0.11 0.19% 2.43 0.11 0.19% compdef
10) 1 1.09 1.09 0.09% 1.09 1.09 0.09% colors
11) 12 0.38 0.03 0.03% 0.38 0.03 0.03% is_plugin
12) 1 0.38 0.38 0.03% 0.38 0.38 0.03% is-at-least
13) 1 0.21 0.21 0.02% 0.21 0.21 0.02% _homebrew-installed
14) 1 0.03 0.03 0.00% 0.03 0.03 0.00% __sdkman_echo_debug
-----------------------------------------------------------------------------------
I was able to measure the total startup time by running time zsh -i -c exit. And the total startup time was almost two seconds.
zsh -i -c exit 1.16s user 0.73s system 100% cpu 1.889 total
As you can see, pyenv takes whole bunch of time (1123 millis!). So I do have the pyenv plugin for ZSH and I did disable it. Here’s what happened afterwards:
num calls time self name
-----------------------------------------------------------------------------------
1) 1 91.42 91.42 53.38% 62.48 62.48 36.48% compinit
2) 2 28.94 14.47 16.90% 28.94 14.47 16.90% compaudit
3) 3 28.62 9.54 16.71% 28.62 9.54 16.71% __sdkman_export_candidate_home
4) 3 27.65 9.22 16.14% 27.65 9.22 16.14% __sdkman_prepend_candidate_to_path
5) 2 8.27 4.14 4.83% 8.27 4.14 4.83% grep-flag-available
6) 2 8.22 4.11 4.80% 8.22 4.11 4.80% env_default
7) 2 2.55 1.28 1.49% 2.55 1.28 1.49% _has
8) 23 2.50 0.11 1.46% 2.50 0.11 1.46% compdef
9) 1 1.24 1.24 0.72% 1.24 1.24 0.72% colors
10) 1 0.41 0.41 0.24% 0.41 0.41 0.24% is-at-least
11) 10 0.37 0.04 0.21% 0.37 0.04 0.21% is_plugin
12) 1 0.02 0.02 0.01% 0.02 0.02 0.01% __sdkman_echo_debug
-----------------------------------------------------------------------------------
zsh -i -c exit 0.28s user 0.23s system 96% cpu 0.526 total
NVM
Not to forget I had NVM installed with the default settings.
With it I had the startup time of 1.9 seconds:
zsh -i -c exit 1.17s user 0.74s system 99% cpu 1.916 total
If you follow this simple instruction or just replace these two lines, initializing NVM in your ~/.zshrc file:
[ -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
with these lines:
if [ -s "$HOME/.nvm/nvm.sh" ] && [ ! "$(type __init_nvm)" = function ]; then
export NVM_DIR="$HOME/.nvm"
[ -s "$NVM_DIR/bash_completion" ] && . "$NVM_DIR/bash_completion"
declare -a __node_commands=('nvm' 'node' 'npm' 'yarn' 'gulp' 'grunt' 'webpack')
function __init_nvm() {
for i in "${__node_commands[@]}"; do unalias $i; done
. "$NVM_DIR"/nvm.sh
unset __node_commands
unset -f __init_nvm
}
for i in "${__node_commands[@]}"; do alias $i='__init_nvm && '$i; done
fi
The start-up time drops by 0.1 second. But it still is an improvement, right?