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[api] Outline keepalive ping logic from APIConnection::loop()

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Extract the keepalive ping/disconnect cold path into a separate
noinline check_keepalive_() method. This code only fires once per
minute but was contributing ~110 bytes to the hot loop() body that
runs every ~16ms.

Results on ESP32 (xtensa):
- loop(): 374 → 263 bytes (-111 bytes, -30%)
- check_keepalive_(): 136 bytes (new, cold path)
- Net: +25 bytes total (call overhead), but the hot path icache
  footprint is significantly reduced.
This commit is contained in:
J. Nick Koston
2026-02-27 23:02:30 -10:00
parent 6c0998f220
commit 2e490d9121
2 changed files with 32 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files
esphome/components/api/api_connection.cpp
+28 -18
View File
@@ -242,24 +242,11 @@ void APIConnection::loop() {
return;
}
if (this->flags_.sent_ping) {
// Disconnect if not responded within 2.5*keepalive
if (now - this->last_traffic_ > KEEPALIVE_DISCONNECT_TIMEOUT) {
on_fatal_error();
this->log_client_(ESPHOME_LOG_LEVEL_WARN, LOG_STR("is unresponsive; disconnecting"));
}
} else if (now - this->last_traffic_ > KEEPALIVE_TIMEOUT_MS && !this->flags_.remove) {
// Only send ping if we're not disconnecting
ESP_LOGVV(TAG, "Sending keepalive PING");
PingRequest req;
this->flags_.sent_ping = this->send_message(req, PingRequest::MESSAGE_TYPE);
if (!this->flags_.sent_ping) {
// If we can't send the ping request directly (tx_buffer full),
// schedule it at the front of the batch so it will be sent with priority
ESP_LOGW(TAG, "Buffer full, ping queued");
this->schedule_message_front_(nullptr, PingRequest::MESSAGE_TYPE, PingRequest::ESTIMATED_SIZE);
this->flags_.sent_ping = true; // Mark as sent to avoid scheduling multiple pings
}
// Keepalive: only call into the cold path when enough time has elapsed.
// When sent_ping is true, last_traffic_ hasn't been updated so this
// condition is already satisfied — covers both send-ping and disconnect cases.
if (now - this->last_traffic_ > KEEPALIVE_TIMEOUT_MS) {
this->check_keepalive_(now);
}
#ifdef USE_API_HOMEASSISTANT_STATES
@@ -275,6 +262,29 @@ void APIConnection::loop() {
#endif
}
void APIConnection::check_keepalive_(uint32_t now) {
// Caller guarantees: now - last_traffic_ > KEEPALIVE_TIMEOUT_MS
if (this->flags_.sent_ping) {
// Disconnect if not responded within 2.5*keepalive
if (now - this->last_traffic_ > KEEPALIVE_DISCONNECT_TIMEOUT) {
on_fatal_error();
this->log_client_(ESPHOME_LOG_LEVEL_WARN, LOG_STR("is unresponsive; disconnecting"));
}
} else if (!this->flags_.remove) {
// Only send ping if we're not disconnecting
ESP_LOGVV(TAG, "Sending keepalive PING");
PingRequest req;
this->flags_.sent_ping = this->send_message(req, PingRequest::MESSAGE_TYPE);
if (!this->flags_.sent_ping) {
// If we can't send the ping request directly (tx_buffer full),
// schedule it at the front of the batch so it will be sent with priority
ESP_LOGW(TAG, "Buffer full, ping queued");
this->schedule_message_front_(nullptr, PingRequest::MESSAGE_TYPE, PingRequest::ESTIMATED_SIZE);
this->flags_.sent_ping = true; // Mark as sent to avoid scheduling multiple pings
}
}
}
void APIConnection::process_active_iterator_() {
// Caller ensures active_iterator_ != NONE
if (this->active_iterator_ == ActiveIterator::LIST_ENTITIES) {
esphome/components/api/api_connection.h
+4
View File
@@ -370,6 +370,10 @@ class APIConnection final : public APIServerConnectionBase {
return this->client_supports_api_version(1, 14) ? MAX_INITIAL_PER_BATCH : MAX_INITIAL_PER_BATCH_LEGACY;
}
// Send keepalive ping or disconnect unresponsive client.
// Cold path — extracted from loop() to reduce instruction cache pressure.
void __attribute__((noinline)) check_keepalive_(uint32_t now);
// Process active iterator (list_entities/initial_state) during connection setup.
// Extracted from loop() — only runs during initial handshake, NONE in steady state.
void __attribute__((noinline)) process_active_iterator_();