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systemd/0699-core-make-manager-event-loop-rate-limit-configurable.patch
Jan Macku 85341d5909 systemd-257-31 
Resolves: RHEL-161564
2026-07-27 09:49:00 +02:00

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From b084721752f93a3077df5b2d12ec3124f82dbc73 Mon Sep 17 00:00:00 2001
From: Michal Sekletar <msekleta@redhat.com>
Date: Wed, 13 May 2026 16:20:55 +0200
Subject: [PATCH] core: make manager event loop rate limit configurable
Co-developed-by: Claude Opus 4.6 <noreply@anthropic.com>
(cherry picked from commit e1c63fd4c0657a7fc7b749c64283ab4dbc6fb39e)
Resolves: RHEL-161564
---
man/org.freedesktop.systemd1.xml | 14 ++++++++++++++
man/systemd-system.conf.xml | 17 +++++++++++++++++
src/core/dbus-manager.c | 2 ++
src/core/main.c | 32 ++++++++++++++++++++++++++++++++
src/core/manager-serialize.c | 3 +++
src/core/manager.c | 3 +--
src/core/manager.h | 2 ++
src/core/system.conf.in | 2 ++
src/core/user.conf.in | 4 +++-
9 files changed, 76 insertions(+), 3 deletions(-)
diff --git a/man/org.freedesktop.systemd1.xml b/man/org.freedesktop.systemd1.xml
index 0b6be4c755..cc50db7f77 100644
--- a/man/org.freedesktop.systemd1.xml
+++ b/man/org.freedesktop.systemd1.xml
@@ -476,6 +476,10 @@ node /org/freedesktop/systemd1 {
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly b DefaultBlockIOAccounting = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
+ readonly t EventLoopRateLimitIntervalUSec = ...;
+ @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
+ readonly u EventLoopRateLimitBurst = ...;
+ @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly b DefaultIOAccounting = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly b DefaultIPAccounting = ...;
@@ -718,6 +722,10 @@ node /org/freedesktop/systemd1 {
<!--property DefaultBlockIOAccounting is not documented!-->
+ <!--property EventLoopRateLimitIntervalUSec is not documented!-->
+
+ <!--property EventLoopRateLimitBurst is not documented!-->
+
<!--property DefaultIOAccounting is not documented!-->
<!--property DefaultIPAccounting is not documented!-->
@@ -1164,6 +1172,10 @@ node /org/freedesktop/systemd1 {
<variablelist class="dbus-property" generated="True" extra-ref="DefaultBlockIOAccounting"/>
+ <variablelist class="dbus-property" generated="True" extra-ref="EventLoopRateLimitIntervalUSec"/>
+
+ <variablelist class="dbus-property" generated="True" extra-ref="EventLoopRateLimitBurst"/>
+
<variablelist class="dbus-property" generated="True" extra-ref="DefaultIOAccounting"/>
<variablelist class="dbus-property" generated="True" extra-ref="DefaultIPAccounting"/>
@@ -12241,6 +12253,8 @@ $ gdbus introspect --system --dest org.freedesktop.systemd1 \
<varname>ShutdownStartTimestamp</varname>,
<varname>ShutdownStartTimestampMonotonic</varname>, and
<varname>SoftRebootsCount</varname> were added in version 256.</para>
+ <para><varname>EventLoopRateLimitIntervalUSec</varname>, and
+ <varname>EventLoopRateLimitBurst</varname> were added in version 261.</para>
</refsect2>
<refsect2>
<title>Unit Objects</title>
diff --git a/man/systemd-system.conf.xml b/man/systemd-system.conf.xml
index 23d09cfb37..1c71e54457 100644
--- a/man/systemd-system.conf.xml
+++ b/man/systemd-system.conf.xml
@@ -625,6 +625,23 @@
<xi:include href="version-info.xml" xpointer="v253"/></listitem>
</varlistentry>
+
+ <varlistentry>
+ <term><varname>EventLoopRateLimitIntervalSec=</varname></term>
+ <term><varname>EventLoopRateLimitBurst=</varname></term>
+
+ <listitem><para>Configures the rate limiting applied to the manager's main event loop. If the event
+ loop iterates more than <varname>EventLoopRateLimitBurst=</varname> times within
+ <varname>EventLoopRateLimitIntervalSec=</varname>, event processing is briefly paused to prevent
+ excessive CPU usage. <varname>EventLoopRateLimitIntervalSec=</varname> defaults to 1s.
+ <varname>EventLoopRateLimitBurst=</varname> defaults to 50000. These settings can also be set on the
+ kernel command line via
+ <varname>systemd.event_loop_ratelimit_interval_sec=</varname> and
+ <varname>systemd.event_loop_ratelimit_burst=</varname>.</para>
+
+ <xi:include href="version-info.xml" xpointer="v261"/></listitem>
+ </varlistentry>
+
</variablelist>
</refsect1>
diff --git a/src/core/dbus-manager.c b/src/core/dbus-manager.c
index d516f30c96..3be3a536fe 100644
--- a/src/core/dbus-manager.c
+++ b/src/core/dbus-manager.c
@@ -3144,6 +3144,8 @@ const sd_bus_vtable bus_manager_vtable[] = {
SD_BUS_PROPERTY("DefaultStartLimitBurst", "u", bus_property_get_unsigned, offsetof(Manager, defaults.start_limit.burst), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("DefaultCPUAccounting", "b", bus_property_get_bool, offsetof(Manager, defaults.cpu_accounting), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("DefaultBlockIOAccounting", "b", bus_property_get_bool, offsetof(Manager, defaults.blockio_accounting), SD_BUS_VTABLE_PROPERTY_CONST),
+ SD_BUS_PROPERTY("EventLoopRateLimitIntervalUSec", "t", bus_property_get_usec, offsetof(Manager, event_loop_ratelimit.interval), SD_BUS_VTABLE_PROPERTY_CONST),
+ SD_BUS_PROPERTY("EventLoopRateLimitBurst", "u", bus_property_get_unsigned, offsetof(Manager, event_loop_ratelimit.burst), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("DefaultIOAccounting", "b", bus_property_get_bool, offsetof(Manager, defaults.io_accounting), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("DefaultIPAccounting", "b", bus_property_get_bool, offsetof(Manager, defaults.ip_accounting), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("DefaultMemoryAccounting", "b", bus_property_get_bool, offsetof(Manager, defaults.memory_accounting), SD_BUS_VTABLE_PROPERTY_CONST),
diff --git a/src/core/main.c b/src/core/main.c
index 506bc00f1d..971ad50b7e 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -160,6 +160,8 @@ static void *arg_random_seed;
static size_t arg_random_seed_size;
static usec_t arg_reload_limit_interval_sec;
static unsigned arg_reload_limit_burst;
+static usec_t arg_event_loop_ratelimit_interval_sec;
+static unsigned arg_event_loop_ratelimit_burst;
/* A copy of the original environment block */
static char **saved_env = NULL;
@@ -569,6 +571,28 @@ static int parse_proc_cmdline_item(const char *key, const char *value, void *dat
return 0;
}
+ } else if (proc_cmdline_key_streq(key, "systemd.event_loop_ratelimit_interval_sec")) {
+
+ if (proc_cmdline_value_missing(key, value))
+ return 0;
+
+ r = parse_sec(value, &arg_event_loop_ratelimit_interval_sec);
+ if (r < 0) {
+ log_warning_errno(r, "Failed to parse systemd.event_loop_ratelimit_interval_sec= argument '%s', ignoring: %m", value);
+ return 0;
+ }
+
+ } else if (proc_cmdline_key_streq(key, "systemd.event_loop_ratelimit_burst")) {
+
+ if (proc_cmdline_value_missing(key, value))
+ return 0;
+
+ r = safe_atou(value, &arg_event_loop_ratelimit_burst);
+ if (r < 0) {
+ log_warning_errno(r, "Failed to parse systemd.event_loop_ratelimit_burst= argument '%s', ignoring: %m", value);
+ return 0;
+ }
+
} else if (streq(key, "quiet") && !value) {
if (arg_show_status == _SHOW_STATUS_INVALID)
@@ -833,6 +857,8 @@ static int parse_config_file(void) {
{ "Manager", "DefaultOOMScoreAdjust", config_parse_oom_score_adjust, 0, NULL },
{ "Manager", "ReloadLimitIntervalSec", config_parse_sec, 0, &arg_reload_limit_interval_sec },
{ "Manager", "ReloadLimitBurst", config_parse_unsigned, 0, &arg_reload_limit_burst },
+ { "Manager", "EventLoopRateLimitIntervalSec", config_parse_sec, 0, &arg_event_loop_ratelimit_interval_sec },
+ { "Manager", "EventLoopRateLimitBurst", config_parse_unsigned, 0, &arg_event_loop_ratelimit_burst },
#if ENABLE_SMACK
{ "Manager", "DefaultSmackProcessLabel", config_parse_string, 0, &arg_defaults.smack_process_label },
#else
@@ -918,6 +944,8 @@ static void set_manager_settings(Manager *m) {
* counter on every daemon-reload. */
m->reload_reexec_ratelimit.interval = arg_reload_limit_interval_sec;
m->reload_reexec_ratelimit.burst = arg_reload_limit_burst;
+ m->event_loop_ratelimit.interval = arg_event_loop_ratelimit_interval_sec;
+ m->event_loop_ratelimit.burst = arg_event_loop_ratelimit_burst;
manager_set_watchdog(m, WATCHDOG_RUNTIME, arg_runtime_watchdog);
manager_set_watchdog(m, WATCHDOG_REBOOT, arg_reboot_watchdog);
@@ -2776,6 +2804,10 @@ static void reset_arguments(void) {
arg_reload_limit_interval_sec = 0;
arg_reload_limit_burst = 0;
+
+ arg_event_loop_ratelimit_interval_sec = 1 * USEC_PER_SEC;
+ arg_event_loop_ratelimit_burst = 50000;
+
}
static void determine_default_oom_score_adjust(void) {
diff --git a/src/core/manager-serialize.c b/src/core/manager-serialize.c
index b225799ed9..a0923b2203 100644
--- a/src/core/manager-serialize.c
+++ b/src/core/manager-serialize.c
@@ -157,6 +157,7 @@ int manager_serialize(
(void) serialize_ratelimit(f, "dump-ratelimit", &m->dump_ratelimit);
(void) serialize_ratelimit(f, "reload-reexec-ratelimit", &m->reload_reexec_ratelimit);
+ (void) serialize_ratelimit(f, "event-loop-ratelimit", &m->event_loop_ratelimit);
(void) serialize_id128(f, "bus-id", m->bus_id);
bus_track_serialize(m->subscribed, f, "subscribed");
@@ -523,6 +524,8 @@ int manager_deserialize(Manager *m, FILE *f, FDSet *fds) {
deserialize_ratelimit(&m->dump_ratelimit, "dump-ratelimit", val);
else if ((val = startswith(l, "reload-reexec-ratelimit=")))
deserialize_ratelimit(&m->reload_reexec_ratelimit, "reload-reexec-ratelimit", val);
+ else if ((val = startswith(l, "event-loop-ratelimit=")))
+ deserialize_ratelimit(&m->event_loop_ratelimit, "event-loop-ratelimit", val);
else if ((val = startswith(l, "soft-reboots-count="))) {
unsigned n;
diff --git a/src/core/manager.c b/src/core/manager.c
index 22efab33df..ef17f873b4 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -3412,7 +3412,6 @@ static int manager_dispatch_jobs_in_progress(sd_event_source *source, usec_t use
}
int manager_loop(Manager *m) {
- RateLimit rl = { .interval = 1*USEC_PER_SEC, .burst = 50000 };
int r;
assert(m);
@@ -3429,7 +3428,7 @@ int manager_loop(Manager *m) {
(void) watchdog_ping();
- if (!ratelimit_below(&rl)) {
+ if (!ratelimit_below(&m->event_loop_ratelimit)) {
/* Yay, something is going seriously wrong, pause a little */
log_warning("Looping too fast. Throttling execution a little.");
sleep(1);
diff --git a/src/core/manager.h b/src/core/manager.h
index 66ad04baf5..63726f70ab 100644
--- a/src/core/manager.h
+++ b/src/core/manager.h
@@ -504,6 +504,8 @@ struct Manager {
RateLimit dump_ratelimit;
sd_event_source *memory_pressure_event_source;
+ /* Rate limit for the manager event loop */
+ RateLimit event_loop_ratelimit;
/* For NFTSet= */
FirewallContext *fw_ctx;
diff --git a/src/core/system.conf.in b/src/core/system.conf.in
index 4fe420c344..f095d5bf8e 100644
--- a/src/core/system.conf.in
+++ b/src/core/system.conf.in
@@ -82,3 +82,5 @@
#DefaultSmackProcessLabel=
#ReloadLimitIntervalSec=
#ReloadLimitBurst=
+#EventLoopRateLimitIntervalSec=1s
+#EventLoopRateLimitBurst=50000
diff --git a/src/core/user.conf.in b/src/core/user.conf.in
index 14f0eae7f8..fa81824c65 100644
--- a/src/core/user.conf.in
+++ b/src/core/user.conf.in
@@ -56,4 +56,6 @@
#DefaultMemoryPressureWatch=auto
#DefaultSmackProcessLabel=
#ReloadLimitIntervalSec=
-#ReloadLimitBurst
+#ReloadLimitBurst=
+#EventLoopRateLimitIntervalSec=1s
+#EventLoopRateLimitBurst=50000
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