[systemd-devel] Plot time data anomalies

[Lennart Poettering]

On Mi, 11.01.23 11:53, Joshua Zivkovic (joshua.zivkovic at codethink.co.uk) wrote:

> Hello,
>
> I've been working on adding JSON and table output to `systemd-analyze
> plot`, to allow programmatic access to the data presented in the SVG
> produced by `systemd-analyze plot`. Whilst using this data I have
> noticed some irregularities in the initialisation times associated with
> a variety of units. It seems as though these units are being activated,
> deactivated and then reactivated because they have recorded
> deactivation times that are before the recorded activation time.
>
> Looking at some of these units, they don't use the `Restart=`
> configuration so it's unusual that they are seemingly being restarted.
>
> These irregularities are dealt with by forcing the values to some other
> recorded value of that unit through a series of conditions in the SVG
> production code.
>
> I'm interested in whether this means that the times for unit
> initialisation, presented by `plot`, aren't entirely accurate and if
> there is anything that can be done about this.

You should read them with a grain of salt. And you should only run the
tool shortly after booting (i.e. where there's a reasonably chance no
service has been restarted yet). If you do it later then the data is
going to be garbage because of the discrepancy between what we
actually track (startup time of most recent invocation) to what people
might expect (startup time of first invocation).

Also note that services that are not referenced by anything (and
didn't fail) might have been unloaded (i.e. "GC'ed"), which means
their startup timing info is released and won't show up in the
displayed data either.

Lennart

--
Lennart Poettering, Berlin