From 591c0e9c6566668d76a4142c0f27aed5fc4b225c Mon Sep 17 00:00:00 2001 From: "J. Nick Koston" Date: Tue, 10 Feb 2026 14:28:26 -0600 Subject: [PATCH] [mdns] Remove mDNS from per-iteration loop on ESP8266 and RP2040 On ESP8266 and RP2040, MDNS.update() was called every loop iteration (~120 Hz) but only manages timer-driven probe/announce state machines. Incoming mDNS packets are handled independently via the lwIP onRx UDP callback and are unaffected by update() frequency. Replace the loop() override with set_interval() at 50ms. This removes the component from the loop list entirely via has_overridden_loop(), eliminating all per-iteration overhead including virtual dispatch. The 50ms interval provides sufficient resolution for all internal timers (shortest is 250ms probe interval per RFC 6762 Section 8.1). --- esphome/components/mdns/mdns_component.h | 25 +++++++++++++++++++++--- esphome/components/mdns/mdns_esp8266.cpp | 11 ++++++++--- esphome/components/mdns/mdns_rp2040.cpp | 11 ++++++++--- 3 files changed, 38 insertions(+), 9 deletions(-) diff --git a/esphome/components/mdns/mdns_component.h b/esphome/components/mdns/mdns_component.h index f696cfff1c..32f8f16ec1 100644 --- a/esphome/components/mdns/mdns_component.h +++ b/esphome/components/mdns/mdns_component.h @@ -45,9 +45,28 @@ class MDNSComponent : public Component { void setup() override; void dump_config() override; -#if (defined(USE_ESP8266) || defined(USE_RP2040)) && defined(USE_ARDUINO) - void loop() override; -#endif + // Polling interval for MDNS.update() on platforms that require it (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 completely removing mDNS from the per-iteration loop list. + // + // 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. + // + // By using set_interval() instead of overriding loop(), the component is excluded from + // the main loop list via has_overridden_loop(), eliminating all per-iteration overhead + // including virtual dispatch. + 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 diff --git a/esphome/components/mdns/mdns_esp8266.cpp b/esphome/components/mdns/mdns_esp8266.cpp index dcbe5ebd52..295a408cbd 100644 --- a/esphome/components/mdns/mdns_esp8266.cpp +++ b/esphome/components/mdns/mdns_esp8266.cpp @@ -36,9 +36,14 @@ static void register_esp8266(MDNSComponent *, StaticVectorsetup_buffers_and_register_(register_esp8266); } - -void MDNSComponent::loop() { MDNS.update(); } +void MDNSComponent::setup() { + this->setup_buffers_and_register_(register_esp8266); + // Schedule MDNS.update() via set_interval() instead of overriding loop(). + // This removes the component from the per-iteration loop list entirely, + // eliminating virtual dispatch overhead on every main loop cycle. + // See MDNS_UPDATE_INTERVAL_MS comment in mdns_component.h for safety analysis. + this->set_interval(MDNS_UPDATE_INTERVAL_MS, []() { MDNS.update(); }); +} void MDNSComponent::on_shutdown() { MDNS.close(); diff --git a/esphome/components/mdns/mdns_rp2040.cpp b/esphome/components/mdns/mdns_rp2040.cpp index e4a9b60cdb..05d991c1fa 100644 --- a/esphome/components/mdns/mdns_rp2040.cpp +++ b/esphome/components/mdns/mdns_rp2040.cpp @@ -35,9 +35,14 @@ static void register_rp2040(MDNSComponent *, StaticVectorsetup_buffers_and_register_(register_rp2040); } - -void MDNSComponent::loop() { MDNS.update(); } +void MDNSComponent::setup() { + this->setup_buffers_and_register_(register_rp2040); + // Schedule MDNS.update() via set_interval() instead of overriding loop(). + // This removes the component from the per-iteration loop list entirely, + // eliminating virtual dispatch overhead on every main loop cycle. + // See MDNS_UPDATE_INTERVAL_MS comment in mdns_component.h for safety analysis. + this->set_interval(MDNS_UPDATE_INTERVAL_MS, []() { MDNS.update(); }); +} void MDNSComponent::on_shutdown() { MDNS.close();