[systemd-devel] Start-up resource and prioritization control

[Umut Tezduyar Lindskog]

Hi,

We are starting many services between basic.target - multi-user.target
at the same time and due to this we are suffering from following two
subjects. What can we do to overcome these problems?

1) We would like to start a subset of services that are scheduled to
start between basic.target - multi-user.target before the rest and
there is no built in way to satisfy our needs.

a) We could use Before=, After= on services but the downside of this
kind of dependency is we have to edit every single service file with
Before=, After= directive. This is not the best option when the subset
of services we would like to start early might change between hardware
or product configuration.

b) The ongoing patch
http://lists.freedesktop.org/archives/systemd-devel/2014-March/018220.html
is promising but it seems to be stopped. Any reason?

c) A service running before basic.target and queriying systemd with
"systemctl show -p [Wants Requires] default.target" and adding
Before=, After= dependency on services on runtime. Doesn't seem so
efficient.


2) Due to starting too many services and due to having frequent
context switches (flushing of caches), we see that boot time is longer
than booting services sequentially.

a) Proposing a configuration to limit the number of jobs that are in
"activating" state.

b) "nice" value of the services can be changed to prioritize things
randomly but then we have to revert back the nice value once the boot
is completed. Doesn't seem so easy.


We are aware that our problem is mostly embedded platform specific. We
could solve our problem staticly with what systemd offers but a static
solution that is customized for one hardware is not the best solution
for another hardware. Having static solutions per hardware is
extremely hard to maintain and we would like to solve this problem
upstream instead of downstream magic.

Thanks,
Umut