to any of these options, the list of
timers is reset, and all prior
assignments will have no
- effect.</para></listitem>
+ effect.</para>
+
+ <para>Note that timers are not
+ necessarily expired at the precise
+ time configured with these settings,
+ as they are subject to the
+ <varname>AccuracySec=</varname>
+ setting below.</para></listitem>
</varlistentry>
<term><varname>OnCalendar=</varname></term>
<listitem><para>Defines realtime
- (i.e. wallclock) timers via calendar
+ (i.e. wallclock) timers with calendar
event expressions. See
<citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>
for more information on the syntax of
calendar event expressions. Otherwise
the semantics are similar to
<varname>OnActiveSec=</varname> and
- related settings.</para></listitem>
+ related settings.</para>
+
+ <para>Note that timers are not
+ necessarily expired at the precise
+ time configured with this setting,
+ as it is subject to the
+ <varname>AccuracySec=</varname>
+ setting below.</para></listitem>
</varlistentry>
+ <varlistentry>
+ <term><varname>AccuracySec=</varname></term>
+
+ <listitem><para>Specify the accuracy
+ the timer shall elapse with. Defaults
+ to 1min. The timer is scheduled to
+ expire within a time window starting
+ with the time specified in
+ <varname>OnCalendar=</varname>,
+ <varname>OnActiveSec=</varname>,
+ <varname>OnBootSec=</varname>,
+ <varname>OnStartupSec=</varname>,
+ <varname>OnUnitActiveSec=</varname> or
+ <varname>OnUnitInactiveSec=</varname>
+ and ending the time configured with
+ <varname>AccuracySec=</varname>
+ later. Within this time window the
+ expiry time will be placed at a
+ host-specific, randomized but stable
+ position, that is synchronized between
+ all local timer units. This is done in
+ order to distribute the wake-up time
+ in networked installations, as well as
+ optimizing power consumption to
+ suppress unnecessary CPU wake-ups. To
+ get best accuracy set this option to
+ 1us. Note that the timer is still
+ subject to the timer slack configured
+ via
+ <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>'s
+ <varname>TimerSlackNSec=</varname>
+ setting. See
+ <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ for details. To optimize power
+ consumption make sure to set this
+ value as high as possible and as low
+ as necessary.</para></listitem>
+ </varlistentry>
<varlistentry>
<term><varname>Unit=</varname></term>
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
</para>
</refsect1>
SD_BUS_PROPERTY("NextElapseUSecRealtime", "t", bus_property_get_usec, offsetof(Timer, next_elapse_monotonic), SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("NextElapseUSecMonotonic", "t", bus_property_get_usec, offsetof(Timer, next_elapse_realtime), SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("Result", "s", property_get_result, offsetof(Timer, result), SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
+ SD_BUS_PROPERTY("AccuracyUSec", "t", bus_property_get_usec, offsetof(Timer, accuracy_usec), 0),
SD_BUS_VTABLE_END
};
t->next_elapse_monotonic = (usec_t) -1;
t->next_elapse_realtime = (usec_t) -1;
+ t->accuracy_usec = USEC_PER_MINUTE;
}
void timer_free_values(Timer *t) {
}
static void timer_dump(Unit *u, FILE *f, const char *prefix) {
+ char buf[FORMAT_TIMESPAN_MAX];
Timer *t = TIMER(u);
Unit *trigger;
TimerValue *v;
fprintf(f,
"%sTimer State: %s\n"
"%sResult: %s\n"
- "%sUnit: %s\n",
+ "%sUnit: %s\n"
+ "%sAccuracy: %s\n",
prefix, timer_state_to_string(t->state),
prefix, timer_result_to_string(t->result),
- prefix, trigger ? trigger->id : "n/a");
+ prefix, trigger ? trigger->id : "n/a",
+ prefix, format_timespan(buf, sizeof(buf), t->accuracy_usec, 1));
LIST_FOREACH(value, v, t->values) {
r = sd_event_source_set_enabled(t->monotonic_event_source, SD_EVENT_ONESHOT);
} else
- r = sd_event_add_monotonic(UNIT(t)->manager->event, t->next_elapse_monotonic, 0, timer_dispatch, t, &t->monotonic_event_source);
+ r = sd_event_add_monotonic(UNIT(t)->manager->event, t->next_elapse_monotonic, t->accuracy_usec, timer_dispatch, t, &t->monotonic_event_source);
if (r < 0)
goto fail;
r = sd_event_source_set_enabled(t->realtime_event_source, SD_EVENT_ONESHOT);
} else
- r = sd_event_add_realtime(UNIT(t)->manager->event, t->next_elapse_realtime, 0, timer_dispatch, t, &t->realtime_event_source);
+ r = sd_event_add_realtime(UNIT(t)->manager->event, t->next_elapse_realtime, t->accuracy_usec, timer_dispatch, t, &t->realtime_event_source);
if (r < 0)
goto fail;