C/C++ • Achieving maximum data throughput with Raspberry Pi 5

Code:

#define _GNU_SOURCE#include <stdio.h>#include <stdlib.h>#include <string.h>#include <fcntl.h>#include <unistd.h>#include <sys/types.h>#include <sys/stat.h>#include <time.h>#include <sys/resource.h>#define BLOCK_SIZE 4096#define FILE_SIZE (30 * 1024 * 1024)  // 30 MB, which is a multiple of BLOCK_SIZE#define NUM_FILES 50int main(int argc, char *argv[]) {    if (argc != 2) {        fprintf(stderr, "Usage: %s <destination_directory>\n", argv[0]);        return 1;    }    char *dest_dir = argv[1];    int fd;    char *buffer;    ssize_t bytes_written;    struct timespec start, end;    // Allocate aligned memory for O_DIRECT for the entire file size    if (posix_memalign((void **)&buffer, BLOCK_SIZE, FILE_SIZE) != 0) {        perror("Error allocating aligned memory");        return 1;    }    memset(buffer, 'A', FILE_SIZE);    struct rusage usage_start, usage_end;    getrusage(RUSAGE_SELF, &usage_start);    clock_gettime(CLOCK_MONOTONIC, &start);    for (int i = 0; i < NUM_FILES; i++) {        char filename[256];        snprintf(filename, sizeof(filename), "%s/testfile_%04d.dat", dest_dir, i);        fd = open(filename, O_WRONLY | O_CREAT | O_DIRECT, 0644);        if (fd == -1) {            perror("Error opening file");            free(buffer);            return 1;        }        bytes_written = write(fd, buffer, FILE_SIZE);        if (bytes_written != FILE_SIZE) {            perror("Error writing to file");            close(fd);            free(buffer);            return 1;        }        close(fd);    }    clock_gettime(CLOCK_MONOTONIC, &end);    free(buffer);    getrusage(RUSAGE_SELF, &usage_end);    double elapsed = (end.tv_sec - start.tv_sec) + (end.tv_nsec - start.tv_nsec) / 1e9;    //double speed = (FILE_SIZE * NUM_FILES) / (1024 * 1024) / elapsed;    double speed = ((long long)FILE_SIZE * NUM_FILES) / (1024.0 * 1024.0) / elapsed;    //printf("Total data written: %d MB\n", (FILE_SIZE * NUM_FILES) / (1024 * 1024));    printf("Total data written: %lld MB\n", ((long long)FILE_SIZE * NUM_FILES) / (1024 * 1024));    printf("Time taken: %.2f seconds\n", elapsed);    printf("Write speed: %.2f MB/s\n", speed);double user_cpu_time_used = (usage_end.ru_utime.tv_sec - usage_start.ru_utime.tv_sec) +                                (usage_end.ru_utime.tv_usec - usage_start.ru_utime.tv_usec) / 1e6;    double system_cpu_time_used = (usage_end.ru_stime.tv_sec - usage_start.ru_stime.tv_sec) +                                  (usage_end.ru_stime.tv_usec - usage_start.ru_stime.tv_usec) / 1e6;    printf("User CPU time used: %.2f seconds\n", user_cpu_time_used);    printf("System CPU time used: %.2f seconds\n", system_cpu_time_used);    return 0;}

Code:

gcc test_speed_multi.c -o test_speed_multi -lrt

Code:

./test_speed_multi /media/SSD/