diff options
| -rw-r--r-- | man/systemd.timer.xml | 43 | ||||
| -rw-r--r-- | src/core/dbus-timer.c | 17 | ||||
| -rw-r--r-- | src/core/load-fragment-gperf.gperf.m4 | 1 | ||||
| -rw-r--r-- | src/core/timer.c | 28 | ||||
| -rw-r--r-- | src/core/timer.h | 1 | ||||
| -rw-r--r-- | src/shared/bus-util.c | 17 |
6 files changed, 101 insertions, 6 deletions
diff --git a/man/systemd.timer.xml b/man/systemd.timer.xml index 5826773a99..fd03bda9cd 100644 --- a/man/systemd.timer.xml +++ b/man/systemd.timer.xml @@ -190,13 +190,12 @@ <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 + 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 + order to optimize 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> @@ -204,6 +203,38 @@ this value as high as possible and as low as necessary.</para></listitem> </varlistentry> + + <varlistentry> + <term><varname>RandomSec=</varname></term> + + <listitem><para>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 each time it is started, 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 + <varname>AccuracySec=</varname> 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 + <varname>RandomSec=</varname> and + <varname>AccuracySec=</varname> are used in conjunction, first + the a randomized time is added, and the result is then + possibly shifted further to coalesce it with other timer + events possibly happening on the system. As mentioned above + <varname>AccuracySec=</varname> defaults to 1min and + <varname>RandomSec=</varname> 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 + <varname>RandomSec=</varname> to a higher value, and + <varname>AccuracySec=1us</varname>.</para></listitem> + </varlistentry> + <varlistentry> <term><varname>Unit=</varname></term> diff --git a/src/core/dbus-timer.c b/src/core/dbus-timer.c index 2e6c479c3a..4bee82df07 100644 --- a/src/core/dbus-timer.c +++ b/src/core/dbus-timer.c @@ -180,6 +180,7 @@ const sd_bus_vtable bus_timer_vtable[] = { BUS_PROPERTY_DUAL_TIMESTAMP("LastTriggerUSec", offsetof(Timer, last_trigger), 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), SD_BUS_VTABLE_PROPERTY_CONST), + SD_BUS_PROPERTY("RandomUSec", "t", bus_property_get_usec, offsetof(Timer, random_usec), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("Persistent", "b", bus_property_get_bool, offsetof(Timer, persistent), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("WakeSystem", "b", bus_property_get_bool, offsetof(Timer, wake_system), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("RemainAfterElapse", "b", bus_property_get_bool, offsetof(Timer, remain_after_elapse), SD_BUS_VTABLE_PROPERTY_CONST), @@ -283,6 +284,22 @@ static int bus_timer_set_transient_property( return 1; + } else if (streq(name, "RandomUSec")) { + usec_t u = 0; + + r = sd_bus_message_read(message, "t", &u); + if (r < 0) + return r; + + if (mode != UNIT_CHECK) { + char time[FORMAT_TIMESPAN_MAX]; + + t->random_usec = u; + unit_write_drop_in_private_format(UNIT(t), mode, name, "RandomSec=%s\n", format_timespan(time, sizeof(time), u, USEC_PER_MSEC)); + } + + return 1; + } else if (streq(name, "WakeSystem")) { int b; diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4 index 0dbe38d7e5..c64850802e 100644 --- a/src/core/load-fragment-gperf.gperf.m4 +++ b/src/core/load-fragment-gperf.gperf.m4 @@ -347,6 +347,7 @@ Timer.Persistent, config_parse_bool, 0, Timer.WakeSystem, config_parse_bool, 0, offsetof(Timer, wake_system) Timer.RemainAfterElapse, config_parse_bool, 0, offsetof(Timer, remain_after_elapse) Timer.AccuracySec, config_parse_sec, 0, offsetof(Timer, accuracy_usec) +Timer.RandomSec, config_parse_sec, 0, offsetof(Timer, random_usec) Timer.Unit, config_parse_trigger_unit, 0, 0 m4_dnl Path.PathExists, config_parse_path_spec, 0, 0 diff --git a/src/core/timer.c b/src/core/timer.c index 0587452cfb..6b0f8e8616 100644 --- a/src/core/timer.c +++ b/src/core/timer.c @@ -27,6 +27,7 @@ #include "dbus-timer.h" #include "fs-util.h" #include "parse-util.h" +#include "random-util.h" #include "special.h" #include "string-table.h" #include "string-util.h" @@ -330,6 +331,28 @@ static usec_t monotonic_to_boottime(usec_t t) { return 0; } +static void add_random(Timer *t, usec_t *v) { + char s[FORMAT_TIMESPAN_MAX]; + usec_t add; + + assert(t); + assert(*v); + + if (t->random_usec == 0) + return; + if (*v == USEC_INFINITY) + return; + + add = random_u64() % t->random_usec; + + if (*v + add < *v) /* overflow */ + *v = (usec_t) -2; /* Highest possible value, that is not USEC_INFINITY */ + else + *v += add; + + log_unit_info(UNIT(t), "Adding %s random time.", format_timespan(s, sizeof(s), add, 0)); +} + static void timer_enter_waiting(Timer *t, bool initial) { bool found_monotonic = false, found_realtime = false; usec_t ts_realtime, ts_monotonic; @@ -452,6 +475,8 @@ static void timer_enter_waiting(Timer *t, bool initial) { char buf[FORMAT_TIMESPAN_MAX]; usec_t left; + add_random(t, &t->next_elapse_monotonic_or_boottime); + left = t->next_elapse_monotonic_or_boottime > ts_monotonic ? t->next_elapse_monotonic_or_boottime - ts_monotonic : 0; log_unit_debug(UNIT(t), "Monotonic timer elapses in %s.", format_timespan(buf, sizeof(buf), left, 0)); @@ -486,6 +511,9 @@ static void timer_enter_waiting(Timer *t, bool initial) { if (found_realtime) { char buf[FORMAT_TIMESTAMP_MAX]; + + add_random(t, &t->next_elapse_realtime); + log_unit_debug(UNIT(t), "Realtime timer elapses at %s.", format_timestamp(buf, sizeof(buf), t->next_elapse_realtime)); if (t->realtime_event_source) { diff --git a/src/core/timer.h b/src/core/timer.h index 6bc9fbed3d..0599f07818 100644 --- a/src/core/timer.h +++ b/src/core/timer.h @@ -58,6 +58,7 @@ struct Timer { Unit meta; usec_t accuracy_usec; + usec_t random_usec; LIST_HEAD(TimerValue, values); usec_t next_elapse_realtime; diff --git a/src/shared/bus-util.c b/src/shared/bus-util.c index dab4934901..38281045b8 100644 --- a/src/shared/bus-util.c +++ b/src/shared/bus-util.c @@ -1442,6 +1442,23 @@ int bus_append_unit_property_assignment(sd_bus_message *m, const char *assignmen return bus_log_create_error(r); return 0; + + } else if (streq(field, "RandomSec")) { + usec_t t; + + r = parse_sec(eq, &t); + if (r < 0) + return log_error_errno(r, "Failed to parse RandomSec= parameter: %s", eq); + + r = sd_bus_message_append_basic(m, SD_BUS_TYPE_STRING, "RandomUSec"); + if (r < 0) + return bus_log_create_error(r); + + r = sd_bus_message_append(m, "v", "t", t); + if (r < 0) + return bus_log_create_error(r); + + return 0; } r = sd_bus_message_append_basic(m, SD_BUS_TYPE_STRING, field); |