kqueue periodic timer confusion
- From: Paul Albrecht <albrecht@xxxxxxxxxx>
- Date: Wed, 11 Jul 2012 14:52:12 -0500
Hi,
Sorry about this repost but I'm confused about the responses I received
in my last post so I'm looking for some clarification.
Specifically, I though I could use the kqueue timer as essentially a
"drop in" replacement for linuxfd_create/read, but was surprised that
the accuracy of the kqueue timer is much less than what I need for my
application.
So my confusion at this point is whether this is consider to be a bug or
"feature"?
Here's some test code if you want to verify the problem:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
int
main(void)
{
int i,msec;
int kq,nev;
struct kevent inqueue;
struct kevent outqueue;
struct timeval start,end;
if ((kq = kqueue()) == -1) {
fprintf(stderr, "kqueue error!? errno = %s", strerror(errno));
exit(EXIT_FAILURE);
}
EV_SET(&inqueue, 1, EVFILT_TIMER, EV_ADD | EV_ENABLE, 0, 20, 0);
gettimeofday(&start, 0);
for (i = 0; i < 50; i++) {
if ((nev = kevent(kq, &inqueue, 1, &outqueue, 1, NULL)) == -1) {
fprintf(stderr, "kevent error!? errno = %s", strerror(errno));
exit(EXIT_FAILURE);
} else if (outqueue.flags & EV_ERROR) {
fprintf(stderr, "EV_ERROR: %s\n", strerror(outqueue.data));
exit(EXIT_FAILURE);
}
}
gettimeofday(&end, 0);
msec = ((end.tv_sec - start.tv_sec) * 1000) + (((1000000 + end.tv_usec - start.tv_usec) / 1000) - 1000);
printf("msec = %d\n", msec);
close(kq);
return EXIT_SUCCESS;
}
--
Paul Albrecht
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