Is it possible to figure out which package/script takes most of the startup time?

Question

I used to run Emacs on Linux using Emacsclient, it is really easy and great experience:

emacs --daemon
emacsclient

When I work on a Windows machine, Emacs starts very slow. It seems there's no default support for emacsclient. So I decide to use the use-package package to reduce Emacs startup time. Since there're several packages, I'd like to know which cost the most startup time, and load it with use-package.

If I am not in the right direction, please correct me.

Answer 1

Since you said you are already using use-package, you can turn on its own verbose option that reports how long each package takes to load.

Use customize-option use-package-verbose or put this in your init file:

(setq use-package-verbose t)

Then restart Emacs and check your *Messages* buffer. The output will look something like:

Loading package dash...done (0.015s)
Loading package ido...done (0.109s)
Loading package company...done (0.125s)
Loading package elisp-slime-nav...done (0.047s)
Loading package smart-mode-line...done (0.046s)

By default times are reported that are longer than 0.01 seconds. You can change this threshold too, see use-package-minimum-reported-time.

Answer 2

This is based on Emacs 24.4.1 (KAEL) on Windows 7 from the emacs-w64 project, but should work on other releases of the same major version. Add this to your .emacs:

(load "server")
(unless (server-running-p) (server-start))

which will run the server if it's not running; taken from here. If you're using cygwin/msys/msys2 then you could add this to your .bashrc:

edit_file() {
        emacsclient -nqa "runemacs.exe" $1 &
}

alias edit=edit_file

or do the equivalent in a batch script for cmd. Now all you've to do is

edit 1.txt   # will start the server, if it's not running
edit 2.txt   # will send a request to the server to open this file

The explanation part is that emacsclient would run runemacs.exe if a server is not running; -q would be to silence it's success message. -n is to not wait for server to return; if not for -n, you should clean up the buffer using server-edit and not the usual kill-buffer.

One additional point is that, if you want to use emacsclient.exe from GUI instead of CLI/TUI then use emacsclientw.exe.