Merge remote-tracking branch 'upstream-ssh/scheduler-pool-unbounded-freelist' into integration

esphome/core/application.cpp

@@ -25,6 +25,10 @@ namespace esphome {
 
 static const char *const TAG = "app";
 
+// Delay after setup() finishes before trimming the scheduler freelist of its post-boot peak.
+// 10 s is well past the bulk of post-setup async work (Wi-Fi/MQTT connects, first-read latency).
+static constexpr uint32_t SCHEDULER_FREELIST_TRIM_DELAY_MS = 10000;
+
 // Helper function for insertion sort of components by priority
 // Using insertion sort instead of std::stable_sort saves ~1.3KB of flash
 // by avoiding template instantiations (std::rotate, std::stable_sort, lambdas)
@@ -112,6 +116,9 @@ void Application::setup() {
 
   ESP_LOGI(TAG, "setup() finished successfully!");
 
+  // Trim the scheduler freelist of its post-boot peak once startup churn settles.
+  this->scheduler.set_timeout(this, SCHEDULER_FREELIST_TRIM_DELAY_MS, [this]() { this->scheduler.trim_freelist(); });
+
 #ifdef USE_SETUP_PRIORITY_OVERRIDE
   // Clear setup priority overrides to free memory
   clear_setup_priority_overrides();

esphome/core/scheduler.cpp

@@ -913,6 +913,38 @@ void Scheduler::recycle_item_main_loop_(SchedulerItem *item) {
 #endif
 }
 
+void Scheduler::trim_freelist() {
+  LockGuard guard{this->lock_};
+  SchedulerItem *item = this->scheduler_item_pool_head_;
+  size_t freed = 0;
+  while (item != nullptr) {
+    SchedulerItem *next = item->next_free;
+    delete item;
+#ifdef ESPHOME_DEBUG_SCHEDULER
+    this->debug_live_items_--;
+#endif
+    item = next;
+    freed++;
+  }
+  this->scheduler_item_pool_head_ = nullptr;
+  this->scheduler_item_pool_size_ = 0;
+
+  // The vectors that back items_/to_add_/defer_queue_ also retain their boot-peak
+  // capacity (std::vector grows by doubling). Swap each with a same-content copy to
+  // reclaim the slack -- the new vector is sized exactly to its current contents.
+  std::vector<SchedulerItem *>(this->items_).swap(this->items_);
+  std::vector<SchedulerItem *>(this->to_add_).swap(this->to_add_);
+#ifndef ESPHOME_THREAD_SINGLE
+  std::vector<SchedulerItem *>(this->defer_queue_).swap(this->defer_queue_);
+#endif
+
+#ifdef ESPHOME_DEBUG_SCHEDULER
+  ESP_LOGD(TAG, "Freelist trimmed (%zu items freed)", freed);
+#else
+  (void) freed;
+#endif
+}
+
 #ifdef ESPHOME_DEBUG_SCHEDULER
 void Scheduler::debug_log_timer_(const SchedulerItem *item, NameType name_type, const char *static_name,
                                  uint32_t hash_or_id, SchedulerItem::Type type, uint32_t delay, uint64_t now) {

esphome/core/scheduler.h

@@ -132,6 +132,12 @@ class Scheduler {
   // @return Timestamp of the last item that ran, or `now` unchanged if none ran.
   uint32_t call(uint32_t now);
 
+  // Reclaim memory held by the post-boot peak. Frees every SchedulerItem in the
+  // recycle freelist and shrinks items_/to_add_/defer_queue_ vector capacity to
+  // their current sizes (std::vector grows by doubling and otherwise retains the
+  // peak). Live items in those vectors are preserved.
+  void trim_freelist();
+
   // Move items from to_add_ into the main heap.
   // IMPORTANT: This method should only be called from the main thread (loop task).
   // Inlined: the fast path (nothing to add) is just an atomic load / empty check.