Date: Wed, 21 Jul 2004 18:13:10 +1000 From: John Birrell <jb@cimlogic.com.au> To: current@freebsd.org Subject: nanosleep returning early Message-ID: <20040721081310.GJ22160@freebsd3.cimlogic.com.au>
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Today I increased HZ in a current kernel to 1000 when adding dummynet.
Now I find that nanosleep regularly comes back a little early.
Can anyone explain why?
I would have expected that the *overrun* beyond the required time to vary,
but never that it would come back early.
------------------
#include <stdio.h>
#include <time.h>
#include <sys/time.h>
#include <unistd.h>
int main(int argc,char *argv[])
{
struct timespec rmt;
struct timespec rqt;
struct timeval abstime;
struct timeval curtime;
gettimeofday(&curtime,NULL);
rqt.tv_sec = 5;
rqt.tv_nsec = 50000000;
abstime.tv_sec = curtime.tv_sec + rqt.tv_sec;
abstime.tv_usec = curtime.tv_usec + rqt.tv_nsec / 1000;
if (abstime.tv_usec >= 1000000) {
abstime.tv_sec += 1;
abstime.tv_usec -= 1000000;
}
printf("curtime %ld.%06ld\n",curtime.tv_sec,curtime.tv_usec);
printf("rqt %ld.%09ld\n",(long) rqt.tv_sec,rqt.tv_nsec);
if (nanosleep(&rqt,&rmt) != 0) {
} else if (gettimeofday(&curtime,NULL) != 0) {
} else if (curtime.tv_sec < abstime.tv_sec || (curtime.tv_sec == abstime.tv_sec && curtime.tv_usec < abstime.tv_usec)) {
printf("Early: curtime %ld.%06ld abstime %ld.%06ld\n",curtime.tv_sec,curtime.tv_usec,abstime.tv_sec,abstime.tv_usec);
}
return(0);
}
------------------
--
John Birrell
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