[arch-general] On-boot delay due to timer units

[Leonid Isaev]

On Thu, 17 Apr 2014 21:31:07 +0200
Thomas Bächler <thomas at archlinux.org> wrote:

> Am 17.04.2014 20:56, schrieb Leonid Isaev:
> > Hi,
> > 
> > Since anacron jobs were replaced with timers, I am seeing a noticeable
> > delay before agetty prompt appears on machines which were unused for some
> > time (due to update/man-db timers starting up simultaneously).
> > 
> > TLDR: Anacron inserts a random delay between boot and running the jobs, so
> > is it possible to simulate this behavior by including e.g. "OnBootSec=..."
> > in the timers at next update? Or is this option incompatible with
> > OnCalendar?
> 
> OnBootSec would cause the timers to always run on boot, no matter how
> much time has passed, which is not what we want.

OK.

> 
> I don't think it is a problem that the timers run on boot, but rather
> that they delay Type=idle units, like agetty. From what the
> documentation says, there should not be any delay:
> 
> "Behavior of idle is very similar to simple; however, actual execution
> of the service binary is delayed until all jobs are dispatched."
> 
> I am confused why get a delay here.

I think the problem is the disk I/O generated due to e.g. man-db indexing,
because I see the hdd light is solid on. So, my guess is that two things can
happen: either the login prompt is delayed, or the prompt is shown but the
actual login will stall.

> 
> I think another solution in systemd would be introducing a holdoff time:
> Instead of running immediately on boot, the timer should be scheduled
> for boot+5min.

You are right -- that's the best way to put it. Except, I'd generate random
timeouts (distributed in some interval) for the corresponding services...

Thanks,
L.

-- 
Leonid Isaev
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