Date: Thu, 2 Oct 2014 13:13:36 -0500 From: Paul Albrecht <palbrecht@glccom.com> To: Adrian Chadd <adrian@freebsd.org> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: freebsd 10 kqueue timer regression Message-ID: <8587D819-AA2F-4387-A4E9-523014384672@glccom.com> In-Reply-To: <CAJ-VmonJQKWeW7K6%2BjY6=FpmZrm%2B6HQOuBmhhjJEapyVpwNFdQ@mail.gmail.com> References: <8ABC0977-FB8F-45E7-ACCC-BFA92EE22E1C@glccom.com> <CAJ-VmonJQKWeW7K6%2BjY6=FpmZrm%2B6HQOuBmhhjJEapyVpwNFdQ@mail.gmail.com>
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On Oct 2, 2014, at 12:18 PM, Adrian Chadd <adrian@freebsd.org> wrote: > On 2 October 2014 08:07, Paul Albrecht <palbrecht@glccom.com> wrote: >>=20 >> Hi, >>=20 >> What=92s up with freebsd 10? I=92m testing some code that uses the = kqueue timer for timing and it doesn=92t work because the precision of = the timer is off. >=20 > Can you provide a test case for it? Here=92s the code: #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 =3D kqueue()) =3D=3D -1) { fprintf(stderr, "kqueue error!? errno =3D %s", = strerror(errno)); exit(EXIT_FAILURE); } EV_SET(&inqueue, 1, EVFILT_TIMER, EV_ADD | EV_ENABLE, 0, 20, 0); gettimeofday(&start, 0); for (i =3D 0; i < 50; i++) { if ((nev =3D kevent(kq, &inqueue, 1, &outqueue, 1, = NULL)) =3D=3D -1) { fprintf(stderr, "kevent error!? errno =3D %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 =3D ((end.tv_sec - start.tv_sec) * 1000) + (((1000000 + = end.tv_usec - start.tv_usec) / 1000) - 1000); printf("msec =3D %d\n", msec); close(kq); return EXIT_SUCCESS; } When I run it on my system I get these results: ./a.out msec =3D 1072 ./a.out msec =3D 1071 ./a.out msec =3D 1071 Which is over about 3.5 times the wait time per second. >=20 > I just chased down one of those recently; maybe it's the same thing > (callout() API changes.) >=20 >=20 > -a
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