[api] Inline DeferredBatch::add_item to eliminate push_back call barrier (#15353)

esphome/components/api/api_connection.cpp

@@ -132,8 +132,6 @@ APIConnection::APIConnection(std::unique_ptr<socket::Socket> sock, APIServer *pa
 #endif
 }
 
-uint32_t APIConnection::get_batch_delay_ms_() const { return this->parent_->get_batch_delay(); }
-
 void APIConnection::start() {
   this->last_traffic_ = App.get_loop_component_start_time();
 
@@ -2072,37 +2070,9 @@ void APIConnection::on_fatal_error() {
   this->flags_.remove = true;
 }
 
-void __attribute__((flatten)) APIConnection::DeferredBatch::push_item(const BatchItem &item) { items.push_back(item); }
+bool APIConnection::schedule_message_front_(EntityBase *entity, uint8_t message_type, uint8_t estimated_size) {
-
+  this->deferred_batch_.add_item_front(entity, message_type, estimated_size);
-void APIConnection::DeferredBatch::add_item(EntityBase *entity, uint8_t message_type, uint8_t estimated_size,
+  return this->schedule_batch_();
-                                            uint8_t aux_data_index) {
-  // Check if we already have a message of this type for this entity
-  // This provides deduplication per entity/message_type combination
-  // O(n) but optimized for RAM and not performance.
-  // Skip deduplication for events - they are edge-triggered, every occurrence matters
-#ifdef USE_EVENT
-  if (message_type != EventResponse::MESSAGE_TYPE)
-#endif
-  {
-    for (const auto &item : items) {
-      if (item.entity == entity && item.message_type == message_type)
-        return;  // Already queued
-    }
-  }
-  // No existing item found (or event), add new one
-  this->push_item({entity, message_type, estimated_size, aux_data_index});
-}
-
-void APIConnection::DeferredBatch::add_item_front(EntityBase *entity, uint8_t message_type, uint8_t estimated_size) {
-  // Add high priority message and swap to front
-  // This avoids expensive vector::insert which shifts all elements
-  // Note: We only ever have one high-priority message at a time (ping OR disconnect)
-  // If we're disconnecting, pings are blocked, so this simple swap is sufficient
-  this->push_item({entity, message_type, estimated_size, AUX_DATA_UNUSED});
-  if (items.size() > 1) {
-    // Swap the new high-priority item to the front
-    std::swap(items.front(), items.back());
-  }
 }
 
 bool APIConnection::send_message_smart_(EntityBase *entity, uint8_t message_type, uint8_t estimated_size,

esphome/components/api/api_connection.h

@@ -644,11 +644,28 @@ class APIConnection final : public APIServerConnectionBase {
 
     // Add item to the batch (with deduplication)
     void add_item(EntityBase *entity, uint8_t message_type, uint8_t estimated_size,
-                  uint8_t aux_data_index = AUX_DATA_UNUSED);
+                  uint8_t aux_data_index = AUX_DATA_UNUSED) {
+      // Dedup: O(n) scan but optimized for RAM over performance
+      // Skip deduplication for events - they are edge-triggered, every occurrence matters
+#ifdef USE_EVENT
+      if (message_type != EventResponse::MESSAGE_TYPE)
+#endif
+      {
+        for (const auto &item : this->items) {
+          if (item.entity == entity && item.message_type == message_type)
+            return;  // Already queued
+        }
+      }
+      this->items.push_back({entity, message_type, estimated_size, aux_data_index});
+    }
     // Add item to the front of the batch (for high priority messages like ping)
-    void add_item_front(EntityBase *entity, uint8_t message_type, uint8_t estimated_size);
+    void add_item_front(EntityBase *entity, uint8_t message_type, uint8_t estimated_size) {
-    // Single push_back site to avoid duplicate _M_realloc_insert instantiation
+      // Swap to front avoids expensive vector::insert which shifts all elements
-    void push_item(const BatchItem &item);
+      this->items.push_back({entity, message_type, estimated_size, AUX_DATA_UNUSED});
+      if (this->items.size() > 1) {
+        std::swap(this->items.front(), this->items.back());
+      }
+    }
 
     // Clear all items
     void clear() {
@@ -713,7 +730,7 @@ class APIConnection final : public APIServerConnectionBase {
   ActiveIterator active_iterator_{ActiveIterator::NONE};
   // Total: 2 (flags) + 2 + 2 + 1 = 7 bytes, then 1 byte padding to next 4-byte boundary
 
-  uint32_t get_batch_delay_ms_() const;
+  uint32_t get_batch_delay_ms_() const { return this->parent_->get_batch_delay(); }
   // Message will use 8 more bytes than the minimum size, and typical
   // MTU is 1500. Sometimes users will see as low as 1460 MTU.
   // If its IPv6 the header is 40 bytes, and if its IPv4
@@ -780,10 +797,8 @@ class APIConnection final : public APIServerConnectionBase {
   }
 
   // Helper function to schedule a high priority message at the front of the batch
-  bool schedule_message_front_(EntityBase *entity, uint8_t message_type, uint8_t estimated_size) {
+  // Out-of-line: callers (on_shutdown, check_keepalive_) are cold paths
-    this->deferred_batch_.add_item_front(entity, message_type, estimated_size);
+  bool schedule_message_front_(EntityBase *entity, uint8_t message_type, uint8_t estimated_size);
-    return this->schedule_batch_();
-  }
 
   // Helper function to log client messages with name and peername
   void log_client_(int level, const LogString *message);