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

Zsh has a profiling module. At the beginning of ~/.zshrc or ~/.zshenv add it like:

# Uncomment to use the profiling module
# zmodload zsh/zprof

Uncomment it, start a new interactive shell then run the command zprof. You will get a detailed list of items you can review to better understand where your performance bottlenecks are:

num  calls                time                       self            name
-----------------------------------------------------------------------------------
 1)    1           7.29     7.29   19.60%      7.29     7.29   19.60%  _p9k_init_ssh
 2)    2           6.72     3.36   18.06%      6.63     3.31   17.81%  gitstatus_start_impl
 3)    1           4.00     4.00   10.75%      4.00     4.00   10.75%  _p9k_must_init
 4)    3          19.28     6.43   51.80%      3.82     1.27   10.28%  (anon)
 5)    1           1.63     1.63    4.37%      1.63     1.63    4.37%  _p9k_restore_state_impl
 6)    1          16.92    16.92   45.46%      1.61     1.61    4.32%  _p9k_precmd_impl
 7)    1           7.13     7.13   19.16%      0.87     0.87    2.33%  _p9k_set_prompt
 8)   22           6.26     0.28   16.83%      0.84     0.04    2.27%  _p9k_build_segment
 9)   17           0.82     0.05    2.19%      0.82     0.05    2.19%  _p9k_param
10)    6           2.24     0.37    6.02%      0.74     0.12    1.98%  _p9k_left_prompt_segment
11)    5           0.59     0.12    1.60%      0.59     0.12    1.60%  add-zsh-hook
12)    1           3.05     3.05    8.20%      0.58     0.58    1.56%  prompt_dir

And here's a one-liner from speeding up zsh you'll appreciate if start time feels sporadic:

for i in $(seq 1 10); do /usr/bin/time zsh -i -c exit; done

Run that job and you should see output like:

        0.05 real         0.02 user         0.02 sys
        0.05 real         0.02 user         0.02 sys
        0.05 real         0.02 user         0.02 sys
        0.05 real         0.02 user         0.02 sys
        0.05 real         0.02 user         0.02 sys
        0.05 real         0.02 user         0.02 sys
        0.05 real         0.02 user         0.02 sys
        0.05 real         0.02 user         0.02 sys
        0.05 real         0.02 user         0.02 sys
        0.05 real         0.02 user         0.02 sys

Profit.