To see how much time was spent in kernelspace and userspace on boot, simply use:
$ systemd-analyze
Tip: If you boot via UEFI and use a boot loader which implements systemd’s Boot Loader Interface (which currently systemd-boot and GRUB do), systemd-analyze can additionally show you how much time was spent in the EFI firmware and the boot loader itself.
To list the started unit files, sorted by the time each of them took to start up:
$ systemd-analyze blame
At some points of the boot process, things can not proceed until a given unit succeeds. To see which units find themselves at these critical points in the startup chain, do:
$ systemd-analyze critical-chain
You can also create an SVG file which describes your boot process graphically, similar to Bootchart:
$ systemd-analyze plot > plot.svg
See systemd-analyze(1) for details.