Basic terminal benchmark program

termbench.c

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <stdint.h>
#include <stdlib.h>

void writestr(int fd, const char* str) {
  write(fd, str, strlen(str));
}

#define LINES_PER_WRITE 128
#define LINE_BUFFER 80
#define TOTAL_BUFFER (LINE_BUFFER*LINES_PER_WRITE)

int main() {
  char str[LINES_PER_WRITE];
  int fd = fileno(stdout);
  memset(str, 'x', LINE_BUFFER);
  str[LINE_BUFFER-1] = '\n';

  char* buffer = malloc(TOTAL_BUFFER);
  for (int i = 0; i < LINES_PER_WRITE; ++i)
    memcpy(buffer + i * LINE_BUFFER, str, LINE_BUFFER);

  int n = 128;
  for (int i = 0; i < 999; ++i) {
    struct timespec before;
    struct timespec after;
    clock_gettime(CLOCK_MONOTONIC, &before);
    writestr(fd, "\x1b[?1049h");
    for (int i = 0; i < n; ++i) {
      write(fd, buffer, TOTAL_BUFFER);
    }
    fsync(fd);
    clock_gettime(CLOCK_MONOTONIC, &after);
    writestr(fd, "\x1b[?1049l");

    uint64_t delta_secs = after.tv_sec - before.tv_sec;
    int64_t delta_nsecs = after.tv_nsec - before.tv_nsec;
    if (delta_nsecs < 0) {
      delta_nsecs += 1000000000;
      delta_secs -= 1;
    }
    delta_nsecs += delta_secs * 1000000000;
    int lines_written = LINES_PER_WRITE * n;
    printf("lines=%d nsecs=l%ld lines/sec=%llu\n", n, delta_nsecs, (lines_written * 1000000000ull) / delta_nsecs);
    if (delta_nsecs > 1000000000)
      break;
    n = (n * 1050000000ull) / delta_nsecs;
  }

  free(buffer);
  return 0;
}