refactor syscall measurement logic and improve command-line argument parsing (9e915abd) · Commits · hpc / syscall_timing

src/opendevnull.cpp

+95 −88

Original line number	Diff line number	Diff line
		@@ -15,7 +15,39 @@ bool always_syscall =
		false; // whether to call the original syscall after the hook
		bool verbose = false; // whether to print debug messages

		int main(int argc, char *argv[]) {

		// Function to measure syscall time
		template <typename PreFunc, typename PostFunc>
		double
		measure_syscall_time(PreFunc pre, PostFunc post, double reps) {
		const int inner_loop_size = 1000000; // Size of the inner loop (1 million)
		int repext =
		static_cast<int>(reps / inner_loop_size); // Outer loop iterations
		int repint = inner_loop_size; // Inner loop iterations
		double remainder = std::fmod(reps, inner_loop_size); // Remaining iterations
		struct timespec start, end;
		clock_gettime(CLOCK_MONOTONIC, &start);

		for(int i = 0; i < repext; ++i) {
		for(int j = 0; j < repint; ++j) {
		auto result = pre();
		post(result);
		}
		}

		for(int j = 0; j < remainder; ++j) {
		auto result = pre();
		post(result);
		}

		clock_gettime(CLOCK_MONOTONIC, &end);
		return (end.tv_sec - start.tv_sec) * 1e6 +
		(end.tv_nsec - start.tv_nsec) / 1e3;
		}


		int
		main(int argc, char* argv[]) {
		// Parse command-line arguments
		std::string syscall;
		for(int i = 1; i < argc; ++i) {
		@@ -24,14 +56,16 @@ int main(int argc, char *argv[]) {
		if(i + 1 < argc) {
		syscall = argv[++i];
		} else {
		std::cerr << "Error: --syscall requires an argument" << std::endl;
		std::cerr << "Error: --syscall requires an argument"
		<< std::endl;
		return 1;
		}
		} else if(arg == "--reps") {
		if(i + 1 < argc) {
		reps = atof(argv[++i]);
		if(reps <= 0) {
		std::cerr << "Error: --reps requires a positive integer" << std::endl;
		std::cerr << "Error: --reps requires a positive integer"
		<< std::endl;
		return 1;
		}
		} else {
		@@ -48,12 +82,6 @@ int main(int argc, char *argv[]) {
		}
		}

		const int inner_loop_size = 1000000; // Size of the inner loop (1 million)
		int repext =
		static_cast<int>(reps / inner_loop_size); // Outer loop iterations
		int repint = inner_loop_size; // Inner loop iterations
		double remainder =
		std::fmod(reps, inner_loop_size); // Remaining iterations

		// Validate that --syscall is provided
		if(syscall.empty()) {
		@@ -61,42 +89,21 @@ int main(int argc, char *argv[]) {
		return 1;
		}

		// Handle the --syscall option
		if (syscall == "open") {

		struct timespec start, end;
		clock_gettime(CLOCK_MONOTONIC, &start);

		for (int i = 0; i < repext; ++i) {
		for (int j = 0; j < repint; ++j) {
		// Handle the --syscall option
		auto pre_open = []() {
		int fd = openat(AT_FDCWD, "/dev/null", O_RDWR, 0);
		if(verbose) {
		std::cout << "open() returned " << fd << std::endl;
		std::cout << "openat() returned " << fd << std::endl;
		}
		return fd;
		};

		auto post_open = [](int fd) {
		close(fd);
		}
		}
		for (int j = 0; j < remainder; ++j) {
		int fd = openat(AT_FDCWD, "/dev/null", O_RDWR, 0);
		if (verbose) {
		std::cout << "open() returned " << fd << std::endl;
		}
		close(fd);
		}

		clock_gettime(CLOCK_MONOTONIC, &end);
		double time_taken =
		(end.tv_sec - start.tv_sec) * 1e6 + (end.tv_nsec - start.tv_nsec) / 1e3;
		};

		std::cout << "Mean time taken: " << time_taken / reps << " microseconds"
		<< std::endl;
		} else if (syscall == "getpid") {
		struct timespec start, end;
		clock_gettime(CLOCK_MONOTONIC, &start);

		for (int i = 0; i < repext; ++i) {
		for (int j = 0; j < repint; ++j) {
		auto pre_getpid = []() {
		int ret = getpid();
		if(verbose) {
		std::cout << "getpid() returned " << ret << std::endl;
		@@ -104,22 +111,22 @@ int main(int argc, char *argv[]) {
		if(always_syscall) {
		syscall_no_intercept(SYS_getpid);
		}
		}
		}
		return ret;
		};

		for (int j = 0; j < remainder; ++j) {
		int ret = getpid();
		if (verbose) {
		std::cout << "getpid() returned " << ret << std::endl;
		}
		if (always_syscall) {
		syscall_no_intercept(SYS_getpid);
		}
		}
		auto post_getpid = [](int) {
		};

		clock_gettime(CLOCK_MONOTONIC, &end);
		double time_taken =
		(end.tv_sec - start.tv_sec) * 1e6 + (end.tv_nsec - start.tv_nsec) / 1e3;
		double time_taken = 0.0;

		if(syscall == "open") {
		time_taken = measure_syscall_time(pre_open, post_open, reps);
		} else if(syscall == "getpid") {
		time_taken = measure_syscall_time(pre_getpid, post_getpid, reps);
		} else {
		std::cerr << "Error: Unsupported syscall '" << syscall << "'" << std::endl;
		return 1;
		}

		std::cout << "Mean time taken: " << time_taken / reps << " microseconds"
		<< std::endl;