[EchoClient] make linked futures optional

While we haven't figured out why the version using linked futures breaks
we can use a simpler implementation which calls submitAndWait on both futures
separately

apps/EchoClient.cpp

@@ -9,7 +9,6 @@
 #include <unistd.h>
 
 #include <algorithm>	// for find
-#include <array>
 #include <atomic>
 #include <cerrno>		 // for errno, ECANCELED
 #include <chrono>		 // for nanoseconds, duration, durat...
@@ -57,6 +56,7 @@ size_t execution_seconds = 0;
 size_t clients = CLIENTS;
 size_t size = SIZE;
 size_t server_backlog = SERVER_BACKLOG;
+bool linked_futures;
 
 std::atomic<bool> terminate = false;
 
@@ -72,6 +72,60 @@ struct ClientResult* clientResults;
 
 struct addrinfo* server;
 
+static auto clientIteration(SendFuture& sendFuture, RecvFuture& recvFuture) -> nanoseconds {
+	auto send_start = high_resolution_clock::now();
+	int32_t bytes_send = sendFuture.submitAndWait();
+	auto send_end = high_resolution_clock::now();
+
+	if (bytes_send < 0) {
+		errno = -bytes_send;
+		DIE_MSG_ERRNO("send failed");
+	}
+
+	auto recv_start = high_resolution_clock::now();
+	int32_t bytes_recv = recvFuture.submitAndWait();
+	auto recv_end = high_resolution_clock::now();
+
+	if (bytes_recv < 0) {
+		errno = -bytes_recv;
+		DIE_MSG_ERRNO("recv failed");
+	}
+
+	return duration_cast<nanoseconds>((send_end - send_start) + (recv_end - recv_start));
+}
+
+static auto clientIterationLinked(SendFuture& sendFuture, RecvFuture& recvFuture) -> nanoseconds {
+	recvFuture.setDependency(sendFuture);
+
+	auto start = high_resolution_clock::now();
+	int32_t res = recvFuture.submitAndWait();
+	auto end = high_resolution_clock::now();
+
+	if (res <= 0) {
+		// recv failed
+		if (res != -ECANCELED) {
+			if (res == 0) {
+				DIE_MSG("server closed the connection");
+			}
+
+			errno = -res;
+			DIE_MSG_ERRNO("receive failed");
+		}
+
+		// send failed
+		int32_t send_res = sendFuture.wait();
+		if (send_res < 0) {
+			errno = -send_res;
+			DIE_MSG_ERRNO("send failed");
+		}
+
+		// send must send less than expected because recvFuture returned -ECANCELED
+		DIE_MSG("short send" << send_res);
+	}
+
+	return duration_cast<nanoseconds>(end - start);
+}
+
 static void clientFunc(uint64_t client_id, Semaphore& readySem, Semaphore& startSem, CPS& cps) {
 	int client_sock = socket(server->ai_family, server->ai_socktype, server->ai_protocol);
 	if (client_sock < 0) {
@@ -94,9 +148,8 @@ static void clientFunc(uint64_t client_id, Semaphore& readySem, Semaphore& start
 		DIE_MSG_ERRNO("setsockopt failed");
 	}
 
-	std::array<char*, 2> buf;
-	buf[0] = new char[size];
-	buf[1] = new char[size];
+	auto* outBuf = new char[size];
+	auto* inBuf = new char[size];
 	uint64_t avg_ns = 0;
 
 	readySem.release();
@@ -104,43 +157,17 @@ static void clientFunc(uint64_t client_id, Semaphore& readySem, Semaphore& start
 
 	size_t i = 0;
 	while (i < iterations && !terminate.load(std::memory_order_relaxed)) {
-		char* outBuf = buf[i % 2];
-		char* inBuf = buf[(i + 1) % 2];
-
 		SendFuture sendFuture(client_sock, outBuf, size, MSG_NOSIGNAL);
 		RecvFuture recvFuture(client_sock, inBuf, size, MSG_WAITALL);
-		recvFuture.setDependency(sendFuture);
-
-		auto start = high_resolution_clock::now();
-		int32_t res = recvFuture.submitAndWait();
-		auto end = high_resolution_clock::now();
-
-		if (res <= 0) {
-			// recv failed
-			if (res != -ECANCELED) {
-				if (res == 0) {
-					DIE_MSG("server closed the connection");
-				}
-
-				errno = -res;
-				DIE_MSG_ERRNO("receive failed");
-			}
-
-			// send failed
-			int32_t send_res = sendFuture.wait();
-			if (send_res < 0) {
-				errno = -send_res;
-				DIE_MSG_ERRNO("send failed");
-			}
-
-			DIE_MSG("short send" << send_res);
-		}
 
-		if (memcmp(outBuf, inBuf, size) != 0) {
-			DIE_MSG("got unexpected echo from server");
+		nanoseconds duration;
+		if (linked_futures) {
+			duration = clientIterationLinked(sendFuture, recvFuture);
+		} else {
+			duration = clientIteration(sendFuture, recvFuture);
 		}
 
-		auto duration = duration_cast<nanoseconds>(end - start);
+		// TODO: replace with emper::math::RunningAverage when !127 is merged
 		uint64_t ns = duration.count();
 		if (unlikely(avg_ns == 0)) {
 			avg_ns = ns;
@@ -149,6 +176,10 @@ static void clientFunc(uint64_t client_id, Semaphore& readySem, Semaphore& start
 			avg_ns /= 2;
 		}
 
+		if (memcmp(outBuf, inBuf, size) != 0) {
+			DIE_MSG("got unexpected echo from server");
+		}
+
 		i++;
 	}
 
@@ -160,8 +191,8 @@ static void clientFunc(uint64_t client_id, Semaphore& readySem, Semaphore& start
 	// cf.setDependency(shut_f);
 	cf.submit();
 
-	delete[] buf[0];
-	delete[] buf[1];
+	delete[] inBuf;
+	delete[] outBuf;
 
 	cf.wait();
 
@@ -186,10 +217,11 @@ static auto existsOption(int argc, char** argv, const std::string& option) -> bo
 }
 
 static void printUsage(char* name) {
-	std::cerr << "Usage: " << name
-						<< "[-h] [-p <port>] [-c <clients>] [-a <address>] [-s <size>] [-b <server backlog>]"
-							 " [-f <output-file>]  [-i <iterations> | -t <execution time in sec>]"
-						<< std::endl;
+	std::cerr
+			<< "Usage: " << name
+			<< "[-h] [-p <port>] [-c <clients>] [-a <address>] [-s <size>] [-b <server backlog>]"
+				 " [-f <output-file>]  [-i <iterations> | -t <execution time in sec>] [--linked-futures]"
+			<< std::endl;
 }
 
 auto main(int argc, char* argv[]) -> int {
@@ -238,6 +270,8 @@ auto main(int argc, char* argv[]) -> int {
 		server_backlog = strtol(server_backlog_s, nullptr, DECIMAL);
 	}
 
+	linked_futures = getOption(argc, argv, "--linked-futures");
+
 	int out_fd = STDOUT_FILENO;
 	char* output_file = getOption(argc, argv, "-f");
 
@@ -293,7 +327,7 @@ auto main(int argc, char* argv[]) -> int {
 			startSemaphore.release();
 		}
 
-		// await the clients
+		// await client termination
 		cps.wait();
 
 		if (execution_seconds) {