This is the test program I've been using to test fsync() latency.
- Ted
/*
* fsync-tester.c
*
* Written by Theodore Ts'o, 3/21/09.
*
* This file may be redistributed under the terms of the GNU Public
* License, version 2.
*/
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <time.h>
#include <fcntl.h>
#include <string.h>
#define SIZE (1024*1024)
static float timeval_subtract(struct timeval *tv1, struct timeval *tv2)
{
return ((tv1->tv_sec - tv2->tv_sec) +
((float) (tv1->tv_usec - tv2->tv_usec)) / 1000000);
}
int main(int argc, char **argv)
{
int fd;
struct timeval tv, tv2;
char buf[SIZE];
fd = open("fsync-tester.tst-file", O_WRONLY|O_CREAT);
if (fd < 0) {
perror("open");
exit(1);
}
memset(buf, 'a', SIZE);
while (1) {
pwrite(fd, buf, SIZE, 0);
gettimeofday(&tv, NULL);
fsync(fd);
gettimeofday(&tv2, NULL);
printf("fsync time: %5.4f\n", timeval_subtract(&tv2, &tv));
sleep(1);
}
}
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