[systemd-devel] Limitation on maximum number of systemd timers that can be active

[P.R.Dinesh]

Thank you very much Lennart for the help.  I was eager to know whether
there was any known limitation, hence this question.

Hi Andy,
I am currently building a diagnostics data collector that collects various
diagnostics data at different scheduled intervals as configured by the
user.
systemd-timer is used for running the schedules. I need to enforce a limit
on the maximum number of schedules the user can use for this feature.
Currently, I am deciding the limit, hence interested in the maximum value
upto which we can allow the user to configure without creating
much/noticeable performance impact.

I will do a performance testing in raspberry pi 3 and share my observation.

Thank you all for your support

On Wed, Feb 3, 2021 at 9:35 PM Lennart Poettering <lennart at poettering.net>
wrote:

> On Mi, 03.02.21 12:16, P.R.Dinesh (pr.dinesh at gmail.com) wrote:
>
> > Do we have any limitation on the maximum number of systemd timers / units
> > that can be active in the system?
>
> We currently enforce a limit of 128K units. This is controlled by
> the MANAGER_MAX_NAMES define, which is hard compiled in.
>
> > Will it consume high cpu/memory if we configure 1000s of systemd timers?
>
> It will consume a bit of memory, but I'd guess it should scale OK.
>
> All scalability issues regarding number of units we saw many years
> ago, by now all slow paths have been fixed I am aware of. I mean, we
> can certainly still optimize stuff (i.e. "systemctl daemon-reload" is
> expensive), but things to my knowledge having a few K of units should
> be totally Ok. (But then again I don't run things like that myself, my
> knowledge is purely based on feedback, or the recent lack thereof)
>
> Lennart
>
> --
> Lennart Poettering, Berlin
>


-- 
With Kind Regards,
P R Dinesh
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