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readfile.c
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readfile.c
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/*
* gcc -o readfile readfile.c -lpthread
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <limits.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <pthread.h>
#include <strings.h>
#include <string.h>
#include <errno.h>
struct thread_data {
char *path;
int chunk_size;
int loops;
int index;
};
void *func_to_run(void *arg)
{
struct thread_data *pd = (struct thread_data *)arg;
int fd;
void *buf = NULL;
int cnt;
ssize_t n;
buf = malloc(pd->chunk_size);
if (!buf) {
printf("thread %u: out of memory.\n", (unsigned int)pthread_self());
return NULL;
}
fd = open(pd->path, O_RDONLY | O_DIRECT, S_IREAD);
if (fd < 0) {
printf("thread %u: unable to open %s [%s].\n", (unsigned int)pthread_self(), pd->path, strerror(errno));
return NULL;
}
for(cnt = 0; cnt < pd->loops; cnt++) {
if(lseek(fd, pd->index * pd->chunk_size, SEEK_SET) < 0) {
printf("thread %u: failed to lseek [%s].\n", (unsigned int)pthread_self(), strerror(errno));
break;
}
n = read(fd, buf, pd->chunk_size);
if (n < 0) {
printf("thread %u: failed to read [%s]\n", (unsigned int)pthread_self(), strerror(errno));
break;
}
}
free(buf);
close(fd);
return NULL;
}
#define DEFAULT_THREADS 10
#define DEFAULT_LOOPS 100000
#define DEFAULT_CHUNKSIZE 1024*1024
void usage(char **argv)
{
printf("Usage:\n");
printf(" %s [-n <threads>] [-l <loops>] [-c <chunk_size>] <path to file>\n", argv[0]);
printf(" -n <threads>: Number of threads to read the same file, default %d\n", DEFAULT_THREADS);
printf(" -l <loops>: Number of loops to repeat the read op, default %d\n", DEFAULT_LOOPS);
printf(" -c <chunk_size>: chunk size of the read op, default %d\n", DEFAULT_CHUNKSIZE);
}
int main(int argc, char **argv)
{
if (argc < 2) {
usage(argv);
exit(1);
}
pthread_t *tids = NULL;
struct thread_data *tdata = NULL;
int nthreads = DEFAULT_THREADS;
int i;
int c;
int ret = 0;
char *path = NULL;
int chunk_size = DEFAULT_CHUNKSIZE;
int loops = DEFAULT_LOOPS;
while ((c = getopt(argc, argv, "n:l:c:")) != -1) {
switch(c) {
case 'n':
nthreads = atoi(optarg);
break;
case 'l':
loops = atoi(optarg);
break;
case 'c':
chunk_size = atoi(optarg);
break;
case ':':
printf("-%c without arg\n", optopt);
exit(1);
break;
default:
exit(2);
}
}
if (optind >= argc) {
fprintf(stderr, "ERROR: missing path.\n");
exit(1);
}
path = argv[optind];
printf("threads = %d\n", nthreads);
printf("loops = %d\n", loops);
printf("chunk_size = %d\n", chunk_size);
printf("path = %s\n", path);
tids = calloc(nthreads, sizeof(pthread_t));
tdata = calloc(nthreads, sizeof(struct thread_data));
for(i = 0; i < nthreads; i++) {
tdata[i].path = path;
tdata[i].chunk_size = chunk_size;
tdata[i].loops = loops;
tdata[i].index = i;
if(pthread_create(&tids[i], NULL, func_to_run, &tdata[i]) != 0) {
fprintf(stderr, "ERROR: failed to create thread\n");
ret = 3;
goto done;
}
}
for(i = 0; i < nthreads; i++) {
(void) pthread_join(tids[i], NULL);
}
done:
if(tids) free(tids);
if(tdata) free(tdata);
printf("DONE.\n");
return(ret);
}