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#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
static pthread_barrier_t barrier;
static unsigned long extent_size;
static unsigned long num_extents;
struct dio_thread_data {
int fd;
int thread_id;
};
static void *dio_thread(void *arg)
{
struct dio_thread_data *data = arg;
off_t off;
ssize_t ret;
void *buf;
if ((errno = posix_memalign(&buf, extent_size / 2, extent_size / 2))) {
perror("malloc");
return NULL;
}
memset(buf, 0, extent_size / 2);
off = (num_extents - 1) * extent_size;
if (data->thread_id)
off += extent_size / 2;
while (off >= 0) {
pthread_barrier_wait(&barrier);
ret = pread(data->fd, buf, extent_size / 2, off);
if (ret == -1)
perror("pread");
off -= extent_size;
}
free(buf);
return NULL;
}
int main(int argc, char **argv)
{
struct dio_thread_data data[2];
pthread_t thread;
int fd;
if (argc != 4) {
fprintf(stderr, "usage: %s EXTENT_SIZE NUM_EXTENTS PATH\n",
argv[0]);
return EXIT_FAILURE;
}
extent_size = strtoul(argv[1], NULL, 0);
num_extents = strtoul(argv[2], NULL, 0);
errno = pthread_barrier_init(&barrier, NULL, 2);
if (errno) {
perror("pthread_barrier_init");
return EXIT_FAILURE;
}
fd = open(argv[3], O_RDONLY | O_DIRECT);
if (fd == -1) {
perror("open");
return EXIT_FAILURE;
}
data[0].fd = fd;
data[0].thread_id = 0;
errno = pthread_create(&thread, NULL, dio_thread, &data[0]);
if (errno) {
perror("pthread_create");
close(fd);
return EXIT_FAILURE;
}
data[1].fd = fd;
data[1].thread_id = 1;
dio_thread(&data[1]);
pthread_join(thread, NULL);
close(fd);
return EXIT_SUCCESS;
}
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