Hello,
I have found that FreeBSD has a very good precision of small sleeps --
what's holding Linux back from doing the same? Using the code snippet below,
FBSD yields between 2 and 80 us on the average while Linux is at
"constantly" ~100 (with HZ=1000) and ~1000 (HZ=100).
Jan Engelhardt
--
#include <sys/time.h>
#include <stdio.h>
#include <time.h>
#define MICROSECOND 1000000
static unsigned long calc_ovcorr(unsigned long ad, int rd) {
struct timespec s = {.tv_sec = 0, .tv_nsec = ad};
struct timeval start, stop;
unsigned long av = 0;
int count = rd;
while(count--) {
gettimeofday(&start, NULL);
nanosleep(&s, NULL);
gettimeofday(&stop, NULL);
av += MICROSECOND * (stop.tv_sec - start.tv_sec) +
stop.tv_usec - start.tv_usec;
}
av /= rd;
fprintf(stderr, " %lu us\n", av);
return av;
}
int main(void) {
calc_ovcorr(0, 100);
return 0;
}
//eof
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