Optimize API component memory usage by reordering class members to reduce padding (#9111)

esphome/components/api/api_connection.cpp

@@ -61,8 +61,8 @@ void APIConnection::start() {
   APIError err = this->helper_->init();
   if (err != APIError::OK) {
     on_fatal_error();
-    ESP_LOGW(TAG, "%s: Helper init failed: %s errno=%d", this->client_combined_info_.c_str(), api_error_to_str(err),
+    ESP_LOGW(TAG, "%s: Helper init failed: %s errno=%d", this->get_client_combined_info().c_str(),
-             errno);
+             api_error_to_str(err), errno);
     return;
   }
   this->client_info_ = helper_->getpeername();
@@ -91,7 +91,7 @@ void APIConnection::loop() {
     // when network is disconnected force disconnect immediately
     // don't wait for timeout
     this->on_fatal_error();
-    ESP_LOGW(TAG, "%s: Network unavailable; disconnecting", this->client_combined_info_.c_str());
+    ESP_LOGW(TAG, "%s: Network unavailable; disconnecting", this->get_client_combined_info().c_str());
     return;
   }
   if (this->next_close_) {
@@ -104,7 +104,7 @@ void APIConnection::loop() {
   APIError err = this->helper_->loop();
   if (err != APIError::OK) {
     on_fatal_error();
-    ESP_LOGW(TAG, "%s: Socket operation failed: %s errno=%d", this->client_combined_info_.c_str(),
+    ESP_LOGW(TAG, "%s: Socket operation failed: %s errno=%d", this->get_client_combined_info().c_str(),
              api_error_to_str(err), errno);
     return;
   }
@@ -118,12 +118,12 @@ void APIConnection::loop() {
     } else if (err != APIError::OK) {
       on_fatal_error();
       if (err == APIError::SOCKET_READ_FAILED && errno == ECONNRESET) {
-        ESP_LOGW(TAG, "%s: Connection reset", this->client_combined_info_.c_str());
+        ESP_LOGW(TAG, "%s: Connection reset", this->get_client_combined_info().c_str());
       } else if (err == APIError::CONNECTION_CLOSED) {
-        ESP_LOGW(TAG, "%s: Connection closed", this->client_combined_info_.c_str());
+        ESP_LOGW(TAG, "%s: Connection closed", this->get_client_combined_info().c_str());
       } else {
-        ESP_LOGW(TAG, "%s: Reading failed: %s errno=%d", this->client_combined_info_.c_str(), api_error_to_str(err),
+        ESP_LOGW(TAG, "%s: Reading failed: %s errno=%d", this->get_client_combined_info().c_str(),
-                 errno);
+                 api_error_to_str(err), errno);
       }
       return;
     } else {
@@ -157,7 +157,7 @@ void APIConnection::loop() {
     // Disconnect if not responded within 2.5*keepalive
     if (now - this->last_traffic_ > (KEEPALIVE_TIMEOUT_MS * 5) / 2) {
       on_fatal_error();
-      ESP_LOGW(TAG, "%s is unresponsive; disconnecting", this->client_combined_info_.c_str());
+      ESP_LOGW(TAG, "%s is unresponsive; disconnecting", this->get_client_combined_info().c_str());
     }
   } else if (now - this->last_traffic_ > KEEPALIVE_TIMEOUT_MS && now > this->next_ping_retry_) {
     ESP_LOGVV(TAG, "Sending keepalive PING");
@@ -166,7 +166,7 @@ void APIConnection::loop() {
       this->next_ping_retry_ = now + ping_retry_interval;
       this->ping_retries_++;
       std::string warn_str = str_sprintf("%s: Sending keepalive failed %u time(s);",
-                                         this->client_combined_info_.c_str(), this->ping_retries_);
+                                         this->get_client_combined_info().c_str(), this->ping_retries_);
       if (this->ping_retries_ >= max_ping_retries) {
         on_fatal_error();
         ESP_LOGE(TAG, "%s disconnecting", warn_str.c_str());
@@ -233,7 +233,7 @@ DisconnectResponse APIConnection::disconnect(const DisconnectRequest &msg) {
   // remote initiated disconnect_client
   // don't close yet, we still need to send the disconnect response
   // close will happen on next loop
-  ESP_LOGD(TAG, "%s disconnected", this->client_combined_info_.c_str());
+  ESP_LOGD(TAG, "%s disconnected", this->get_client_combined_info().c_str());
   this->next_close_ = true;
   DisconnectResponse resp;
   return resp;
@@ -1544,8 +1544,7 @@ bool APIConnection::try_send_log_message(int level, const char *tag, const char
 HelloResponse APIConnection::hello(const HelloRequest &msg) {
   this->client_info_ = msg.client_info;
   this->client_peername_ = this->helper_->getpeername();
-  this->client_combined_info_ = this->client_info_ + " (" + this->client_peername_ + ")";
+  this->helper_->set_log_info(this->get_client_combined_info());
-  this->helper_->set_log_info(this->client_combined_info_);
   this->client_api_version_major_ = msg.api_version_major;
   this->client_api_version_minor_ = msg.api_version_minor;
   ESP_LOGV(TAG, "Hello from client: '%s' | %s | API Version %" PRIu32 ".%" PRIu32, this->client_info_.c_str(),
@@ -1567,7 +1566,7 @@ ConnectResponse APIConnection::connect(const ConnectRequest &msg) {
   // bool invalid_password = 1;
   resp.invalid_password = !correct;
   if (correct) {
-    ESP_LOGD(TAG, "%s connected", this->client_combined_info_.c_str());
+    ESP_LOGD(TAG, "%s connected", this->get_client_combined_info().c_str());
     this->connection_state_ = ConnectionState::AUTHENTICATED;
     this->parent_->get_client_connected_trigger()->trigger(this->client_info_, this->client_peername_);
 #ifdef USE_HOMEASSISTANT_TIME
@@ -1673,7 +1672,7 @@ bool APIConnection::try_to_clear_buffer(bool log_out_of_space) {
   APIError err = this->helper_->loop();
   if (err != APIError::OK) {
     on_fatal_error();
-    ESP_LOGW(TAG, "%s: Socket operation failed: %s errno=%d", this->client_combined_info_.c_str(),
+    ESP_LOGW(TAG, "%s: Socket operation failed: %s errno=%d", this->get_client_combined_info().c_str(),
              api_error_to_str(err), errno);
     return false;
   }
@@ -1695,10 +1694,10 @@ bool APIConnection::send_buffer(ProtoWriteBuffer buffer, uint16_t message_type)
   if (err != APIError::OK) {
     on_fatal_error();
     if (err == APIError::SOCKET_WRITE_FAILED && errno == ECONNRESET) {
-      ESP_LOGW(TAG, "%s: Connection reset", this->client_combined_info_.c_str());
+      ESP_LOGW(TAG, "%s: Connection reset", this->get_client_combined_info().c_str());
     } else {
-      ESP_LOGW(TAG, "%s: Packet write failed %s errno=%d", this->client_combined_info_.c_str(), api_error_to_str(err),
+      ESP_LOGW(TAG, "%s: Packet write failed %s errno=%d", this->get_client_combined_info().c_str(),
-               errno);
+               api_error_to_str(err), errno);
     }
     return false;
   }
@@ -1707,11 +1706,11 @@ bool APIConnection::send_buffer(ProtoWriteBuffer buffer, uint16_t message_type)
 }
 void APIConnection::on_unauthenticated_access() {
   this->on_fatal_error();
-  ESP_LOGD(TAG, "%s requested access without authentication", this->client_combined_info_.c_str());
+  ESP_LOGD(TAG, "%s requested access without authentication", this->get_client_combined_info().c_str());
 }
 void APIConnection::on_no_setup_connection() {
   this->on_fatal_error();
-  ESP_LOGD(TAG, "%s requested access without full connection", this->client_combined_info_.c_str());
+  ESP_LOGD(TAG, "%s requested access without full connection", this->get_client_combined_info().c_str());
 }
 void APIConnection::on_fatal_error() {
   this->helper_->close();
@@ -1860,10 +1859,10 @@ void APIConnection::process_batch_() {
   if (err != APIError::OK && err != APIError::WOULD_BLOCK) {
     on_fatal_error();
     if (err == APIError::SOCKET_WRITE_FAILED && errno == ECONNRESET) {
-      ESP_LOGW(TAG, "%s: Connection reset during batch write", this->client_combined_info_.c_str());
+      ESP_LOGW(TAG, "%s: Connection reset during batch write", this->get_client_combined_info().c_str());
     } else {
-      ESP_LOGW(TAG, "%s: Batch write failed %s errno=%d", this->client_combined_info_.c_str(), api_error_to_str(err),
+      ESP_LOGW(TAG, "%s: Batch write failed %s errno=%d", this->get_client_combined_info().c_str(),
-               errno);
+               api_error_to_str(err), errno);
     }
   }
 

esphome/components/api/api_connection.h

@@ -275,7 +275,13 @@ class APIConnection : public APIServerConnection {
   bool try_to_clear_buffer(bool log_out_of_space);
   bool send_buffer(ProtoWriteBuffer buffer, uint16_t message_type) override;
 
-  std::string get_client_combined_info() const { return this->client_combined_info_; }
+  std::string get_client_combined_info() const {
+    if (this->client_info_ == this->client_peername_) {
+      // Before Hello message, both are the same (just IP:port)
+      return this->client_info_;
+    }
+    return this->client_info_ + " (" + this->client_peername_ + ")";
+  }
 
   // Buffer allocator methods for batch processing
   ProtoWriteBuffer allocate_single_message_buffer(uint16_t size);
@@ -432,37 +438,44 @@ class APIConnection : public APIServerConnection {
   // Helper function to get estimated message size for buffer pre-allocation
   static uint16_t get_estimated_message_size(uint16_t message_type);
 
-  enum class ConnectionState {
+  // Pointers first (4 bytes each, naturally aligned)
+  std::unique_ptr<APIFrameHelper> helper_;
+  APIServer *parent_;
+
+  // 4-byte aligned types
+  uint32_t last_traffic_;
+  uint32_t next_ping_retry_{0};
+  int state_subs_at_ = -1;
+
+  // Strings (12 bytes each on 32-bit)
+  std::string client_info_;
+  std::string client_peername_;
+
+  // 2-byte aligned types
+  uint16_t client_api_version_major_{0};
+  uint16_t client_api_version_minor_{0};
+
+  // Group all 1-byte types together to minimize padding
+  enum class ConnectionState : uint8_t {
     WAITING_FOR_HELLO,
     CONNECTED,
     AUTHENTICATED,
   } connection_state_{ConnectionState::WAITING_FOR_HELLO};
-
+  uint8_t log_subscription_{ESPHOME_LOG_LEVEL_NONE};
   bool remove_{false};
-
-  std::unique_ptr<APIFrameHelper> helper_;
-
-  std::string client_info_;
-  std::string client_peername_;
-  std::string client_combined_info_;
-  uint32_t client_api_version_major_{0};
-  uint32_t client_api_version_minor_{0};
-#ifdef USE_ESP32_CAMERA
-  esp32_camera::CameraImageReader image_reader_;
-#endif
-
   bool state_subscription_{false};
-  int log_subscription_{ESPHOME_LOG_LEVEL_NONE};
-  uint32_t last_traffic_;
-  uint32_t next_ping_retry_{0};
-  uint8_t ping_retries_{0};
   bool sent_ping_{false};
   bool service_call_subscription_{false};
   bool next_close_ = false;
-  APIServer *parent_;
+  uint8_t ping_retries_{0};
+  // 8 bytes used, no padding needed
+
+  // Larger objects at the end
   InitialStateIterator initial_state_iterator_;
   ListEntitiesIterator list_entities_iterator_;
-  int state_subs_at_ = -1;
+#ifdef USE_ESP32_CAMERA
+  esp32_camera::CameraImageReader image_reader_;
+#endif
 
   // Function pointer type for message encoding
   using MessageCreatorPtr = uint16_t (*)(EntityBase *, APIConnection *, uint32_t remaining_size, bool is_single);

esphome/components/api/api_frame_helper.h

@@ -125,38 +125,6 @@ class APIFrameHelper {
     const uint8_t *current_data() const { return data.data() + offset; }
   };
 
-  // Queue of data buffers to be sent
-  std::deque<SendBuffer> tx_buf_;
-
-  // Common state enum for all frame helpers
-  // Note: Not all states are used by all implementations
-  // - INITIALIZE: Used by both Noise and Plaintext
-  // - CLIENT_HELLO, SERVER_HELLO, HANDSHAKE: Only used by Noise protocol
-  // - DATA: Used by both Noise and Plaintext
-  // - CLOSED: Used by both Noise and Plaintext
-  // - FAILED: Used by both Noise and Plaintext
-  // - EXPLICIT_REJECT: Only used by Noise protocol
-  enum class State {
-    INITIALIZE = 1,
-    CLIENT_HELLO = 2,  // Noise only
-    SERVER_HELLO = 3,  // Noise only
-    HANDSHAKE = 4,     // Noise only
-    DATA = 5,
-    CLOSED = 6,
-    FAILED = 7,
-    EXPLICIT_REJECT = 8,  // Noise only
-  };
-
-  // Current state of the frame helper
-  State state_{State::INITIALIZE};
-
-  // Helper name for logging
-  std::string info_;
-
-  // Socket for communication
-  socket::Socket *socket_{nullptr};
-  std::unique_ptr<socket::Socket> socket_owned_;
-
   // Common implementation for writing raw data to socket
   APIError write_raw_(const struct iovec *iov, int iovcnt);
 
@@ -169,15 +137,41 @@ class APIFrameHelper {
   APIError write_raw_(const struct iovec *iov, int iovcnt, socket::Socket *socket, std::vector<uint8_t> &tx_buf,
                       const std::string &info, StateEnum &state, StateEnum failed_state);
 
+  // Pointers first (4 bytes each)
+  socket::Socket *socket_{nullptr};
+  std::unique_ptr<socket::Socket> socket_owned_;
+
+  // Common state enum for all frame helpers
+  // Note: Not all states are used by all implementations
+  // - INITIALIZE: Used by both Noise and Plaintext
+  // - CLIENT_HELLO, SERVER_HELLO, HANDSHAKE: Only used by Noise protocol
+  // - DATA: Used by both Noise and Plaintext
+  // - CLOSED: Used by both Noise and Plaintext
+  // - FAILED: Used by both Noise and Plaintext
+  // - EXPLICIT_REJECT: Only used by Noise protocol
+  enum class State : uint8_t {
+    INITIALIZE = 1,
+    CLIENT_HELLO = 2,  // Noise only
+    SERVER_HELLO = 3,  // Noise only
+    HANDSHAKE = 4,     // Noise only
+    DATA = 5,
+    CLOSED = 6,
+    FAILED = 7,
+    EXPLICIT_REJECT = 8,  // Noise only
+  };
+
+  // Containers (size varies, but typically 12+ bytes on 32-bit)
+  std::deque<SendBuffer> tx_buf_;
+  std::string info_;
+  std::vector<struct iovec> reusable_iovs_;
+  std::vector<uint8_t> rx_buf_;
+
+  // Group smaller types together
+  uint16_t rx_buf_len_ = 0;
+  State state_{State::INITIALIZE};
   uint8_t frame_header_padding_{0};
   uint8_t frame_footer_size_{0};
-
+  // 5 bytes total, 3 bytes padding
-  // Reusable IOV array for write_protobuf_packets to avoid repeated allocations
-  std::vector<struct iovec> reusable_iovs_;
-
-  // Receive buffer for reading frame data
-  std::vector<uint8_t> rx_buf_;
-  uint16_t rx_buf_len_ = 0;
 
   // Common initialization for both plaintext and noise protocols
   APIError init_common_();
@@ -213,19 +207,28 @@ class APINoiseFrameHelper : public APIFrameHelper {
   APIError init_handshake_();
   APIError check_handshake_finished_();
   void send_explicit_handshake_reject_(const std::string &reason);
+
+  // Pointers first (4 bytes each)
+  NoiseHandshakeState *handshake_{nullptr};
+  NoiseCipherState *send_cipher_{nullptr};
+  NoiseCipherState *recv_cipher_{nullptr};
+
+  // Shared pointer (8 bytes on 32-bit = 4 bytes control block pointer + 4 bytes object pointer)
+  std::shared_ptr<APINoiseContext> ctx_;
+
+  // Vector (12 bytes on 32-bit)
+  std::vector<uint8_t> prologue_;
+
+  // NoiseProtocolId (size depends on implementation)
+  NoiseProtocolId nid_;
+
+  // Group small types together
   // Fixed-size header buffer for noise protocol:
   // 1 byte for indicator + 2 bytes for message size (16-bit value, not varint)
   // Note: Maximum message size is UINT16_MAX (65535), with a limit of 128 bytes during handshake phase
   uint8_t rx_header_buf_[3];
   uint8_t rx_header_buf_len_ = 0;
-
+  // 4 bytes total, no padding
-  std::vector<uint8_t> prologue_;
-
-  std::shared_ptr<APINoiseContext> ctx_;
-  NoiseHandshakeState *handshake_{nullptr};
-  NoiseCipherState *send_cipher_{nullptr};
-  NoiseCipherState *recv_cipher_{nullptr};
-  NoiseProtocolId nid_;
 };
 #endif  // USE_API_NOISE
 
@@ -252,6 +255,12 @@ class APIPlaintextFrameHelper : public APIFrameHelper {
 
  protected:
   APIError try_read_frame_(ParsedFrame *frame);
+
+  // Group 2-byte aligned types
+  uint16_t rx_header_parsed_type_ = 0;
+  uint16_t rx_header_parsed_len_ = 0;
+
+  // Group 1-byte types together
   // Fixed-size header buffer for plaintext protocol:
   // We now store the indicator byte + the two varints.
   // To match noise protocol's maximum message size (UINT16_MAX = 65535), we need:
@@ -263,8 +272,7 @@ class APIPlaintextFrameHelper : public APIFrameHelper {
   uint8_t rx_header_buf_[6];  // 1 byte indicator + 5 bytes for varints (3 for size + 2 for type)
   uint8_t rx_header_buf_pos_ = 0;
   bool rx_header_parsed_ = false;
-  uint16_t rx_header_parsed_type_ = 0;
+  // 8 bytes total, no padding needed
-  uint16_t rx_header_parsed_len_ = 0;
 };
 #endif
 

esphome/components/api/api_server.h

@@ -142,19 +142,27 @@ class APIServer : public Component, public Controller {
   }
 
  protected:
-  bool shutting_down_ = false;
+  // Pointers and pointer-like types first (4 bytes each)
   std::unique_ptr<socket::Socket> socket_ = nullptr;
-  uint16_t port_{6053};
+  Trigger<std::string, std::string> *client_connected_trigger_ = new Trigger<std::string, std::string>();
+  Trigger<std::string, std::string> *client_disconnected_trigger_ = new Trigger<std::string, std::string>();
+
+  // 4-byte aligned types
   uint32_t reboot_timeout_{300000};
   uint32_t batch_delay_{100};
   uint32_t last_connected_{0};
+
+  // Vectors and strings (12 bytes each on 32-bit)
   std::vector<std::unique_ptr<APIConnection>> clients_;
   std::string password_;
   std::vector<uint8_t> shared_write_buffer_;  // Shared proto write buffer for all connections
   std::vector<HomeAssistantStateSubscription> state_subs_;
   std::vector<UserServiceDescriptor *> user_services_;
-  Trigger<std::string, std::string> *client_connected_trigger_ = new Trigger<std::string, std::string>();
+
-  Trigger<std::string, std::string> *client_disconnected_trigger_ = new Trigger<std::string, std::string>();
+  // Group smaller types together
+  uint16_t port_{6053};
+  bool shutting_down_ = false;
+  // 3 bytes used, 1 byte padding
 
 #ifdef USE_API_NOISE
   std::shared_ptr<APINoiseContext> noise_ctx_ = std::make_shared<APINoiseContext>();