Test vfs measurement activity with stap script.

mmaptest.c

/* I can be built with gcc -o mmaptest mmaptest.c -O0 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <err.h>
#include <sysexits.h>

#include <sys/stat.h>
#include <sys/mman.h>
#include <fcntl.h>

#define FILENAME "./test_map.bin"
#define MAP_SIZE 1048576

int main(const int argc, const char **argv) {
  int fd = -1, i=0;
  int shareflag = 0;
  char *map = NULL;
  char r=0, w=0;

  if (argc < 2)
    errx(EX_SOFTWARE, "Must supply the argument 'private' or 'shared' to determine map mode");

  if (strncmp(argv[1], "shared", 8) == 0)
    shareflag = MAP_SHARED;
  else
  if (strncmp(argv[1], "private", 8) == 0)
    shareflag = MAP_PRIVATE;
  else
    errx(EX_SOFTWARE, "Must supply the argument 'private' or 'shared' to determine map mode");

  /* Create the file */
  if ((fd = open(FILENAME, O_CLOEXEC|O_RDWR|O_CREAT, S_IRUSR|S_IWUSR)) < 0)
    err(EX_OSERR, "Cannot create file %s", FILENAME);

  /* Make this file the right size */
  if (ftruncate(fd, MAP_SIZE))
    err(EX_OSERR, "Cannot truncate file %s", FILENAME);

  printf("File has been created.\n");

  /* Map the file, close the fd, unlink the file */
  if ((map = mmap(NULL, MAP_SIZE, PROT_READ|PROT_WRITE, shareflag, fd, 0)) == MAP_FAILED)
    err(EX_OSERR, "Could not create memory map");
  close(fd);
  fd = -1;

  if (unlink(FILENAME))
    errx(EX_OSERR, "Could not delete the filename %s", FILENAME);

  printf("Map has been generated\n");

  /* Do it */
  while (1) {
    printf("Doing map work..\n");
    for (i=0; i < MAP_SIZE; i++) {
      r = map[i];
      map[i] = w++ % 256;
    }
    usleep(500000);
  }

  exit(0);
}