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Diffstat (limited to 'man')
| -rw-r--r-- | man/systemd.xml | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/man/systemd.xml b/man/systemd.xml index 77aade8158..b166e534a5 100644 --- a/man/systemd.xml +++ b/man/systemd.xml @@ -392,6 +392,25 @@ <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry> for details about these target units.</para> + <para>systemd only keeps a minimal set of units loaded into memory. Specifically, the only units that are kept + loaded into memory are those for which at least one of the following conditions is true:</para> + + <orderedlist> + <listitem><para>It is in an active, activating, deactivating or failed state (i.e. in any unit state except for <literal>dead</literal>)</para></listitem> + <listitem><para>It has a job queued for it</para></listitem> + <listitem><para>It is a dependency of some sort of at least one other unit that is loaded into memory</para></listitem> + <listitem><para>It has some form of resource still allocated (e.g. a service unit that is inactive but for which + a process is still lingering that ignored the request to be terminated)</para></listitem> + <listitem><para>It has been pinned into memory programmatically by a D-Bus call</para></listitem> + </orderedlist> + + <para>systemd will automatically and implicitly load units from disk — if they are not loaded yet — as soon as + operations are requested for them. Thus, in many respects, the fact whether a unit is loaded or not is invisible to + clients. Use <command>systemctl list-units --all</command> to comprehensively list all units currently loaded. Any + unit for which none of the conditions above applies is promptly unloaded. Note that when a unit is unloaded from + memory its accounting data is flushed out too. However, this data is generally not lost, as a journal log record + is generated declaring the consumed resources whenever a unit shuts down.</para> + <para>Processes systemd spawns are placed in individual Linux control groups named after the unit which they belong to in the private systemd hierarchy. (see <ulink |