Can I profile my .zshrc/.zshenv?

Question

It seems like my shell is taking way too long to start up. Is there any way to profile it so I can figure out what\'s slowing it down so much?

Answer 1

You can start your timer at the first suspicious point in your ~/.zshrc (or at the beginning):

integer t0=$(date '+%s')  # move this around
... maybe something suspect ...

# End of zshrc
function {
    local -i t1 startup
    t1=$(date '+%s')
    startup=$(( t1 - t0 ))
    [[ $startup -gt 1 ]] && print "Hmm, poor shell startup time: $startup"
}
unset t0

This alerts me if ever I see a too-slow startup, and I leave it in as a permanent wrapper.

For more sophisticated measurements, there is a zsh module called zprof. It's as simple as temporarily wrapping the contents of your ~/.zshrc in a zmodload zsh/zprof and zprof. This will dump some verbose profiling tables that are easy enough to interpret.

More info in zshmodules(1) manpage.

When I find things that are particularly slow (rbenv init, vcs_info check-for-changes, antigen, nvm, zsh-mime-setup, interpreter version checking, etc) I add SLOW comments as reminders, and try to find workarounds. Slow startups can cause a lot grief, so I tend to avoid zsh packages/framewords whose inner workings I don't grok. compinit is the slowest thing I'm willing to live with and is ~half of total startup time.