From 706fdc66fb9cfeba7f1f0e00cc914ff69026757f Mon Sep 17 00:00:00 2001 From: "J. Nick Koston" Date: Sun, 8 Mar 2026 08:38:16 -1000 Subject: [PATCH] [scheduler] Use std::atomic instead of std::atomic for remove flag GCC on Xtensa (ESP32) generates an indirect function call for std::atomic::load() instead of inlining it. This adds unnecessary call overhead on the scheduler hot path where the remove flag is checked multiple times per loop iteration. std::atomic::load() inlines correctly on all platforms, producing a simple load instruction with memory barrier. This eliminates 5 indirect calls and saves 30 bytes of flash on the scheduler hot path. --- esphome/core/scheduler.h | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/esphome/core/scheduler.h b/esphome/core/scheduler.h index cefbdd1b223..eb6cea4f37d 100644 --- a/esphome/core/scheduler.h +++ b/esphome/core/scheduler.h @@ -178,9 +178,11 @@ class Scheduler { uint16_t next_execution_high_; // Upper 16 bits (millis_major counter) #ifdef ESPHOME_THREAD_MULTI_ATOMICS - // Multi-threaded with atomics: use atomic for lock-free access - // Place atomic separately since it can't be packed with bit fields - std::atomic remove{false}; + // Multi-threaded with atomics: use atomic uint8_t for lock-free access. + // std::atomic is not used because GCC on Xtensa generates an indirect + // function call for std::atomic::load() instead of inlining it. + // std::atomic inlines correctly on all platforms. + std::atomic remove{0}; // Bit-packed fields (4 bits used, 4 bits padding in 1 byte) enum Type : uint8_t { TIMEOUT, INTERVAL } type : 1; @@ -204,7 +206,7 @@ class Scheduler { next_execution_low_(0), next_execution_high_(0), #ifdef ESPHOME_THREAD_MULTI_ATOMICS - // remove is initialized in the member declaration as std::atomic{false} + // remove is initialized in the member declaration type(TIMEOUT), name_type_(NameType::STATIC_STRING), is_retry(false) { @@ -508,7 +510,7 @@ class Scheduler { // Multi-threaded with atomics: use atomic store with appropriate ordering // Release ordering when setting to true ensures cancellation is visible to other threads // Relaxed ordering when setting to false is sufficient for initialization - item->remove.store(removed, removed ? std::memory_order_release : std::memory_order_relaxed); + item->remove.store(removed ? 1 : 0, removed ? std::memory_order_release : std::memory_order_relaxed); #else // Single-threaded (ESPHOME_THREAD_SINGLE) or // multi-threaded without atomics (ESPHOME_THREAD_MULTI_NO_ATOMICS): direct write