On-demand starting/stopping of cups [was: [Blueprint client-1305-printing-stack-with-mobile-in-mind] Printing Stack with Mobile in Mind]

[Dimitri John Ledkov]

On 4 February 2014 06:12, Martin Pitt <martin.pitt at ubuntu.com> wrote:
> Hello Till, all,
>
> thanks for picking this up and pioneering on-demand startup in Ubuntu!
> Unfortunately cups is probably the most complicated case for on-demand
> startup, so I have some remarks.
>
> Till Kamppeter [2014-02-03 18:11 -0000]:
>> Blueprint changed by Till Kamppeter:
>>
>> Whiteboard changed:
>> + tkamppeter, 2014-02-03:
>> +
>> + (After discussion with xnox on Desktop Sprint) For on-demand starting of
>> + daemons (avahi-daemon, cups, cups-browsed) instead of using Upstart
>> + bridges (which can get rather complex and is still buggy in Upstart) let
>> + them get started when the user opens the print dialog. Queues in the
>> + network get all visible within around 5 seconds. Stop daemons when
>> + dialog is closed, but let CUPS keep running for printing the job(s).
>> + CUPS has then to remove temporary queues and close by itself when queues
>> + empty out.
>
> Will this only be done on the phone or the desktop as well? I want to
> point out that starting daemons several times on demand like that is
> not universally better than always having them running as we do now.
> It trades using less memory against using more CPU/IO/battery as now
> the daemon loading, linking, and initialization has to be done several
> times.
>
> In a system with swap or plenty of memory (i. e. laptops) where you
> want to optimize for power it's generally better to not constantly
> stop and start services.
>
> On a phone this makes much more sense of course, as printing from a
> phone is a rare task, memory is usually scarce, and there usually is
> no swap.
>
> The initial starting on demand is always fine of course, provided that
> picking up remote printers is really that fast (it used to be 30
> seconds with the old browsing protocol?). So perhaps as a compromise,
> on a phone cups could still immediately quit after finishing its jobs,
> but on a desktop it would just keep running for e. g. an hour before
> it times out?
>
> I assume cups would never auto-quit and always auto-start at boot if
> you have printers that get shared remotely?
>

Yes, auto-quit is done when no queues are shared to remote clients and
all queues are empty.

Regards,

Dimitri.