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再论精确延时(usleep,nanosleep,select)
/*
make: gcc -o test_sleep test_sleep.c
*/
/* #include "comm_main.h" */
#include <stdio.h>;
#include <stdlib.h>;
#include <time.h>;
#include <sys/time.h>;
#include <errno.h>;
#include <string.h>;
#include <unistd.h>;
#include <sys/types.h>;
#define PRINT_USEAGE { \
fprintf(stderr,"\n Usage: %s usec ",argv[0]); \
fprintf(stderr,"\n\n" ;\
}
int
main (int argc, char **argv)
{
unsigned int nTimeTestSec = 0; /* sec */
unsigned int nTimeTest = 0; /* usec */
struct timeval tvBegin;
struct timeval tvNow;
int ret = 0;
unsigned int nDelay = 0; /* usec */
fd_set rfds;
struct timeval tv;
int fd = 1;
int i = 0;
struct timespec req;
unsigned int delay[20] =
{ 500000, 100000, 50000, 10000, 1000, 900, 500, 100, 10, 1, 0 };
int nReduce = 0; /* 误差 */
#if 0
if (argc < 2)
{
PRINT_USEAGE;
exit (1);
}
nDelay = atoi (argv[1]);
#endif
fprintf (stderr, "%18s%12s%12s%12s\n", "function", "time(usec)", "realTime",
"reduce";
fprintf (stderr,
"-------------------------------------------------------------------\n";
for (i = 0; i < 20; i++)
{
if (delay <= 0)
break;
nDelay = delay;
/* test usleep */
gettimeofday (&tvBegin, NULL);
ret = usleep (nDelay);
if (-1 == ret)
{
fprintf (stderr, " usleep error . errno=%d [%s]\n", errno,
strerror (errno));
}
gettimeofday (&tvNow, NULL);
nTimeTest =
(tvNow.tv_sec - tvBegin.tv_sec) * 1000000 + tvNow.tv_usec -
tvBegin.tv_usec;
nReduce = nTimeTest - nDelay;
fprintf (stderr, "\t usleep %8u %8u %8d\n", nDelay, nTimeTest,
nReduce);
/* test nanosleep */
gettimeofday (&tvBegin, NULL);
req.tv_sec = nDelay / 1000000;
req.tv_nsec = (nDelay % 1000000) * 1000;
ret = nanosleep (&req, NULL);
if (-1 == ret)
{
fprintf (stderr, "\t nanosleep %8u not support\n", nDelay);
}
else
{
gettimeofday (&tvNow, NULL);
nTimeTest =
(tvNow.tv_sec - tvBegin.tv_sec) * 1000000 + tvNow.tv_usec -
tvBegin.tv_usec;
nReduce = nTimeTest - nDelay;
fprintf (stderr, "\t nanosleep %8u %8u %8d\n", nDelay,
nTimeTest, nReduce);
}
/* test select */
gettimeofday (&tvBegin, NULL);
FD_ZERO (&rfds);
FD_SET (fd, &rfds);
tv.tv_sec = 0;
tv.tv_usec = nDelay;
ret = select (0, NULL, NULL, NULL, &tv);
if (-1 == ret)
{
fprintf (stderr, " select error . errno=%d [%s]\n", errno,
strerror (errno));
}
gettimeofday (&tvNow, NULL);
nTimeTest =
(tvNow.tv_sec - tvBegin.tv_sec) * 1000000 + tvNow.tv_usec -
tvBegin.tv_usec;
nReduce = nTimeTest - nDelay;
fprintf (stderr, "\t select %8u %8u %8d\n", nDelay, nTimeTest,
nReduce);
}
return 0;
} |
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发表于 2004-06-04 11:06
