diff --git a/NEWS b/NEWS
index ba92740d7c..4bda0b2977 100644
--- a/NEWS
+++ b/NEWS
@@ -159,11 +159,9 @@ CHANGES WITH 247 in spe:
to the service.
* Timer units gained a new FixedRandomDelay= boolean setting. If
- enabled the random delay configured with RandomizedDelaySec= is
- hashed from the unit name, system identity, and execution context, so
- that always the same offset is used for the same unit on the same
- system run in the same context, in a way that is stable across system
- reboots.
+ enabled, the random delay configured with RandomizedDelaySec= is
+ selected in a way that is stable on a given system (though still
+ different for different units).
* Socket units gained a new setting Timestamping= that takes "us", "ns"
or "off". This controls the SO_TIMESTAMP/SO_TIMESTAMPNS socket
diff --git a/man/systemd.timer.xml b/man/systemd.timer.xml
index 7c1a4917e5..9fe7ff3255 100644
--- a/man/systemd.timer.xml
+++ b/man/systemd.timer.xml
@@ -240,44 +240,41 @@
RandomizedDelaySec=
- Delay the timer by a randomly selected, evenly
- distributed amount of time between 0 and the specified time
- value. Defaults to 0, indicating that no randomized delay
- shall be applied. Each timer unit will determine this delay
- randomly before each iteration, and the delay will simply be
- added on top of the next determined elapsing time. This is
- useful to stretch dispatching of similarly configured timer
- events over a certain amount time, to avoid that they all fire
- at the same time, possibly resulting in resource
- congestion. Note the relation to
- AccuracySec= above: the latter allows the
- service manager to coalesce timer events within a specified
- time range in order to minimize wakeups, the former does the
- opposite: it stretches timer events over a time range, to make
- it unlikely that they fire simultaneously. If
- RandomizedDelaySec= and
- AccuracySec= are used in conjunction, first
- the randomized delay is added, and then the result is
- possibly further shifted to coalesce it with other timer
- events happening on the system. As mentioned above
- AccuracySec= defaults to 1min and
- RandomizedDelaySec= to 0, thus encouraging
- coalescing of timer events. In order to optimally stretch
- timer events over a certain range of time, make sure to set
- RandomizedDelaySec= to a higher value, and
- AccuracySec=1us.
+ Delay the timer by a randomly selected, evenly distributed amount of time between 0
+ and the specified time value. Defaults to 0, indicating that no randomized delay shall be applied.
+ Each timer unit will determine this delay randomly before each iteration, and the delay will simply
+ be added on top of the next determined elapsing time, unless modified with
+ FixedRandomDelay=, see below.
+
+ This setting is useful to stretch dispatching of similarly configured timer events over a
+ certain time interval, to prevent them from firing all at the same time, possibly resulting in
+ resource congestion.
+
+ Note the relation to AccuracySec= above: the latter allows the service
+ manager to coalesce timer events within a specified time range in order to minimize wakeups, while
+ this setting does the opposite: it stretches timer events over an interval, to make it unlikely that
+ they fire simultaneously. If RandomizedDelaySec= and
+ AccuracySec= are used in conjunction, first the randomized delay is added, and
+ then the result is possibly further shifted to coalesce it with other timer events happening on the
+ system. As mentioned above AccuracySec= defaults to 1 minute and
+ RandomizedDelaySec= to 0, thus encouraging coalescing of timer events. In order to
+ optimally stretch timer events over a certain range of time, set
+ AccuracySec=1us and RandomizedDelaySec= to some higher value.
+ FixedRandomDelay=
- Takes a boolean argument. If true, some amount of time between 0 and
- RandomizedDelaySec= is chosen and added as the delay for each timer iteration. As this
- delay will not be recalculated on each run, this effectively creates a fixed offset for each iteration.
- The distribution between 0 and RandomizedDelaySec= is deterministic and based on
- a combination of the machine ID, whether the timer is run by the user/system manager, the service manager's
- user ID, and the timer's unit name. Has no effect if
- RandomizedDelaySec= is set to 0. Defaults to .
+ Takes a boolean argument. When enabled, the randomized offset specified by
+ RandomizedDelaySec= is reused for all firings of the same timer. For a given timer
+ unit, the offset depends on the machine ID, user identifier and timer name, which means that it is
+ stable between restarts of the manager. This effectively creates a fixed offset for an individual
+ timer, reducing the jitter in firings of this timer, while still avoiding firing at the same time as
+ other similarly configured timers.
+
+ This setting has no effect if RandomizedDelaySec= is set to 0. Defaults to
+ .