Merge branch 'mdns-throttle-update-polling' into integration

esphome/components/mdns/mdns_component.h

@@ -48,6 +48,25 @@ class MDNSComponent : public Component {
 #if (defined(USE_ESP8266) || defined(USE_RP2040)) && defined(USE_ARDUINO)
   void loop() override;
 #endif
+
+  // Throttle interval for MDNS.update() on platforms that require polling (ESP8266, RP2040).
+  //
+  // On these platforms, MDNS.update() calls _process(true) which only manages timer-driven
+  // state machines (probe/announce timeouts and service query cache TTLs). Incoming mDNS
+  // packets are handled independently via the lwIP onRx UDP callback and are NOT affected
+  // by how often update() is called.
+  //
+  // The shortest internal timer is the 250ms probe interval (RFC 6762 Section 8.1).
+  // Announcement intervals are 1000ms and cache TTL checks are on the order of seconds
+  // to minutes. A 50ms polling interval provides sufficient resolution for all timers
+  // while reducing CPU overhead by ~84% compared to calling every loop iteration.
+  //
+  // In steady state (after the ~8 second boot probe/announce phase completes), update()
+  // checks timers that are set to never expire, making every call pure overhead.
+  //
+  // Tasmota uses a 50ms main loop cycle with mDNS working correctly, confirming this
+  // interval is safe in production.
+  static constexpr uint32_t MDNS_UPDATE_INTERVAL_MS = 50;
   float get_setup_priority() const override { return setup_priority::AFTER_CONNECTION; }
 
 #ifdef USE_MDNS_EXTRA_SERVICES
@@ -110,6 +129,9 @@ class MDNSComponent : public Component {
 #endif
 #ifdef USE_MDNS_STORE_SERVICES
   StaticVector<MDNSService, MDNS_SERVICE_COUNT> services_{};
+#endif
+#if (defined(USE_ESP8266) || defined(USE_RP2040)) && defined(USE_ARDUINO)
+  uint32_t last_update_{0};
 #endif
   void compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUNT> &services, char *mac_address_buf);
 };

esphome/components/mdns/mdns_esp8266.cpp

@@ -38,7 +38,17 @@ static void register_esp8266(MDNSComponent *, StaticVector<MDNSService, MDNS_SER
 
 void MDNSComponent::setup() { this->setup_buffers_and_register_(register_esp8266); }
 
-void MDNSComponent::loop() { MDNS.update(); }
+void MDNSComponent::loop() {
+  // Throttle MDNS.update() to avoid calling it every loop iteration (~120 Hz).
+  // The update() function only manages timer-driven probe/announce state machines
+  // and service query cache TTLs. Incoming mDNS packets are processed independently
+  // via the lwIP onRx callback and do not depend on update() frequency.
+  const uint32_t now = App.get_loop_component_start_time();
+  if (now - this->last_update_ < MDNS_UPDATE_INTERVAL_MS)
+    return;
+  this->last_update_ = now;
+  MDNS.update();
+}
 
 void MDNSComponent::on_shutdown() {
   MDNS.close();

esphome/components/mdns/mdns_rp2040.cpp

@@ -37,7 +37,17 @@ static void register_rp2040(MDNSComponent *, StaticVector<MDNSService, MDNS_SERV
 
 void MDNSComponent::setup() { this->setup_buffers_and_register_(register_rp2040); }
 
-void MDNSComponent::loop() { MDNS.update(); }
+void MDNSComponent::loop() {
+  // Throttle MDNS.update() to avoid calling it every loop iteration (~120 Hz).
+  // The update() function only manages timer-driven probe/announce state machines
+  // and service query cache TTLs. Incoming mDNS packets are processed independently
+  // via the lwIP onRx callback and do not depend on update() frequency.
+  const uint32_t now = App.get_loop_component_start_time();
+  if (now - this->last_update_ < MDNS_UPDATE_INTERVAL_MS)
+    return;
+  this->last_update_ = now;
+  MDNS.update();
+}
 
 void MDNSComponent::on_shutdown() {
   MDNS.close();