[benchmark] Add plaintext API frame write benchmarks (#15036)

tests/benchmarks/components/api/bench_plaintext_frame.cpp

@@ -0,0 +1,162 @@
+#include "esphome/core/defines.h"
+#ifdef USE_API_PLAINTEXT
+
+#include <benchmark/benchmark.h>
+#include <fcntl.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include "esphome/components/api/api_frame_helper_plaintext.h"
+#include "esphome/components/api/api_pb2.h"
+#include "esphome/components/api/api_buffer.h"
+
+namespace esphome::api::benchmarks {
+
+static constexpr int kInnerIterations = 2000;
+
+// Helper to drain accumulated data from the read side of a socket
+// to prevent the write side from blocking.
+static void drain_socket(int fd) {
+  char buf[65536];
+  while (::read(fd, buf, sizeof(buf)) > 0) {
+  }
+}
+
+// Helper to create a TCP loopback connection with an APIPlaintextFrameHelper
+// on the write end. Returns the helper and the read-side fd.
+// Uses real TCP sockets so TCP_NODELAY succeeds during init().
+static std::pair<std::unique_ptr<APIPlaintextFrameHelper>, int> create_plaintext_helper() {
+  // Create a TCP listener on loopback
+  int listen_fd = ::socket(AF_INET, SOCK_STREAM, 0);
+  int opt = 1;
+  ::setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
+
+  struct sockaddr_in addr {};
+  addr.sin_family = AF_INET;
+  addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+  addr.sin_port = 0;  // OS-assigned port
+  ::bind(listen_fd, reinterpret_cast<struct sockaddr *>(&addr), sizeof(addr));
+  ::listen(listen_fd, 1);
+
+  // Get the assigned port
+  socklen_t addr_len = sizeof(addr);
+  ::getsockname(listen_fd, reinterpret_cast<struct sockaddr *>(&addr), &addr_len);
+
+  // Connect from client side
+  int write_fd = ::socket(AF_INET, SOCK_STREAM, 0);
+  ::connect(write_fd, reinterpret_cast<struct sockaddr *>(&addr), sizeof(addr));
+
+  // Accept on server side (this is our read fd)
+  int read_fd = ::accept(listen_fd, nullptr, nullptr);
+  ::close(listen_fd);
+
+  // Make both ends non-blocking
+  int flags = ::fcntl(write_fd, F_GETFL, 0);
+  ::fcntl(write_fd, F_SETFL, flags | O_NONBLOCK);
+  flags = ::fcntl(read_fd, F_GETFL, 0);
+  ::fcntl(read_fd, F_SETFL, flags | O_NONBLOCK);
+
+  // Increase socket buffer sizes to reduce drain frequency
+  int bufsize = 1024 * 1024;
+  ::setsockopt(write_fd, SOL_SOCKET, SO_SNDBUF, &bufsize, sizeof(bufsize));
+  ::setsockopt(read_fd, SOL_SOCKET, SO_RCVBUF, &bufsize, sizeof(bufsize));
+
+  auto sock = std::make_unique<socket::Socket>(write_fd);
+  auto helper = std::make_unique<APIPlaintextFrameHelper>(std::move(sock));
+  helper->init();
+
+  return {std::move(helper), read_fd};
+}
+
+// --- Write a single SensorStateResponse through plaintext framing ---
+// Measures the full write path: header construction, varint encoding,
+// iovec assembly, and socket write.
+
+static void PlaintextFrame_WriteSensorState(benchmark::State &state) {
+  auto [helper, read_fd] = create_plaintext_helper();
+  uint8_t padding = helper->frame_header_padding();
+
+  // Pre-init buffer to typical TCP MSS size to avoid benchmarking
+  // heap allocation — in real use the buffer is reused across writes.
+  APIBuffer buffer;
+  buffer.reserve(1460);
+
+  for (auto _ : state) {
+    for (int i = 0; i < kInnerIterations; i++) {
+      buffer.clear();
+      SensorStateResponse msg;
+      msg.key = 0x12345678;
+      msg.state = 23.5f;
+      msg.missing_state = false;
+
+      uint32_t size = msg.calculate_size();
+      buffer.resize(padding + size);
+      ProtoWriteBuffer writer(&buffer, padding);
+      msg.encode(writer);
+
+      helper->write_protobuf_packet(SensorStateResponse::MESSAGE_TYPE, writer);
+
+      if ((i & 0xFF) == 0)
+        drain_socket(read_fd);
+    }
+    drain_socket(read_fd);
+    benchmark::DoNotOptimize(helper.get());
+  }
+  state.SetItemsProcessed(state.iterations() * kInnerIterations);
+
+  ::close(read_fd);
+}
+BENCHMARK(PlaintextFrame_WriteSensorState);
+
+// --- Write a batch of 5 SensorStateResponses in one call ---
+// Measures batched write: multiple messages assembled into one writev.
+
+static void PlaintextFrame_WriteBatch5(benchmark::State &state) {
+  auto [helper, read_fd] = create_plaintext_helper();
+  uint8_t padding = helper->frame_header_padding();
+  uint8_t footer = helper->frame_footer_size();
+
+  // Pre-init buffer to typical TCP MSS size to avoid benchmarking
+  // heap allocation — in real use the buffer is reused across writes.
+  APIBuffer buffer;
+  buffer.reserve(1460);
+
+  for (auto _ : state) {
+    for (int i = 0; i < kInnerIterations; i++) {
+      buffer.clear();
+      MessageInfo messages[5] = {{0, 0, 0}, {0, 0, 0}, {0, 0, 0}, {0, 0, 0}, {0, 0, 0}};
+
+      for (int j = 0; j < 5; j++) {
+        uint16_t offset = buffer.size();
+        SensorStateResponse msg;
+        msg.key = static_cast<uint32_t>(j);
+        msg.state = 23.5f + static_cast<float>(j);
+        msg.missing_state = false;
+
+        uint32_t size = msg.calculate_size();
+        buffer.resize(offset + padding + size + footer);
+        ProtoWriteBuffer writer(&buffer, offset + padding);
+        msg.encode(writer);
+
+        messages[j] = MessageInfo(SensorStateResponse::MESSAGE_TYPE, offset, size);
+      }
+
+      helper->write_protobuf_messages(ProtoWriteBuffer(&buffer, 0), std::span<const MessageInfo>(messages, 5));
+
+      if ((i & 0xFF) == 0)
+        drain_socket(read_fd);
+    }
+    drain_socket(read_fd);
+    benchmark::DoNotOptimize(helper.get());
+  }
+  state.SetItemsProcessed(state.iterations() * kInnerIterations);
+
+  ::close(read_fd);
+}
+BENCHMARK(PlaintextFrame_WriteBatch5);
+
+}  // namespace esphome::api::benchmarks
+
+#endif  // USE_API_PLAINTEXT