Bug#763601: systemd: booting is extremely slow depending on order of "console" arguments to kernel

[Sven Ulland]

I'm hitting the same problem. I can reproduce it on systemd 215 and
sysv 2.88.

On Jessie with systemd 215, there is a consistent 30 second pause
between each line of output, and this regular output seems to be due
to systemd actually writing lots of output, seemingly via the kernel
kprintf function, which is directed to the IPMI serial-over-LAN (SoL)
console.

On Wheezy with sysv 2.88, there is nearly no output at all, since that
init system doesn't print using the kernel kprintf output. So there
are long pauses in between bursts of kernel console messages. I've
never really waited until init completion, since it takes such a long
time.

The issue seems to be related to how I configure my Dell C8220
server's serial console settings: In an attempt to make it wire the
IPMI serial-over-LAN (SoL) console to COM1 (3F8h) so that I could use
ttyS0 for the kernel console and also the getty login, I modified the
'serial_port_address' BIOS setting using the 'setupbios' tool, to the
value '2f8h_3f8h' (default value is '3f8h_2f8h'). This will remap the
COM port addresses, so that the internal SoL port ends up on COM1, and
the front/back physical port ends up on COM2 (but only after the BIOS
stage has completed). This is contrary to the default setup, where
COM1 connects to the physical port, and COM2 to the SoL port.

Rewriting the Linux kernel command line from:

   console=tty0 console=ttyS0,115200

to:

   console=ttyS0,115200 console=tty0

fixes the boot-up speed, but leaves the SoL console blank after having
written all the kernel console output: no getty is reachable/visible
on it, even if the getty processes are correctly running, both on
ttyS0 and ttyS1, at the correct baud rates.

Leaving the 'serial_port_address' BIOS setting at its default value of
'3f8h_2f8h' will make the boot-up work fine, with *either* order:

   console=tty0 console=ttyS0,115200 # OK!
   console=ttyS0,115200 console=tty0 # OK!

Carsten: Did you figure out anything more about the issue?

Sven