[systemd-devel] Understanding systemd-analyze's plots

[Stefan Majewsky]

Hi,

my openSUSE 12.1 system boots in about 30 seconds, and I wanted to cut
that time down a bit, so I took a look at systemd-analyze's blame and
plot output.

But I do not really know how to interpret the results which I see in
the plot [1]. The startup sequence takes 20.5 seconds in userspace, of
which only the last 3 seconds seem to be spent on what I consider "the
interesting stuff": starting all sorts of services and finally
bringing up KDM.

The rest of the time seems to be spent activating the hardware,
various mounts and udev. (According to the LED on my notebook's case,
the disk is busy all the time.) To put my confusion into questions:

1. Why does the system need 6 seconds (from t=6.3s to t=12.3s on the
plot) to activate some tmpfs mounts?

2. Why is localnet.service activating for a whole 7 seconds? I looked
into it, it's only a SysV init script that sets hostname and
domainname from the config in /etc, yet it's number 1 in
systemd-analyze blame.

3. Why does it look like about nothing happens between t=13s and t=22s?

It might be that openSUSE's unit files (or SysV leftovers) are not yet
optimized for the early boot: For example, I seem to have saved some
seconds by masking lvm.service (I don't use LVM at all). But that
won't explain why systemd is actually slower on this stage of boot vs.
the old SysV init some distro versions ago.

Can someone enlighten me?

Greetings
Stefan

[1] http://imgur.com/3U4tg