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/*

* test minimum select time

*

* ./prog usec [method [duration]]

*/

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <string.h>

#include <sys/time.h>

#include <poll.h>

#include <inttypes.h>

enum { M_SELECT =0 , M_POLL, M_USLEEP };

static const char *names[] = { "select", "poll", "usleep" };

int

main(int argc, char *argv[])

{

struct timeval ta, tb, prev;

int usec = 1, total = 0, method = M_SELECT;

uint32_t *vals = NULL;

uint32_t i, count = 0;

#define LIM 1000000

if (argc > 1)

usec = atoi(argv[1]);

if (usec <= 0)

usec = 1;

else if (usec > 500000)

usec = 500000;

if (argc > 2) {

if (!strcmp(argv[2], "poll"))

method = M_POLL;

else if (!strcmp(argv[2], "usleep"))

method = M_USLEEP;

}

if (argc > 3)

total = atoi(argv[3]);

if (total < 1)

total = 1;

else if (total > 10)

total = 10;

fprintf(stderr, "testing %s for %dus over %ds\n",

names[method], usec, total);

gettimeofday(&ta, NULL);

prev = ta;

vals = calloc(LIM, sizeof(uint32_t));

for (;;) {

if (method == M_SELECT) {

struct timeval to = { 0, usec };

select(0, NULL, NULL, NULL, &to);

} else if (method == M_POLL) {

poll(NULL, 0, usec/1000);

} else {

usleep(usec);

}

gettimeofday(&tb, NULL);

timersub(&tb, &prev, &prev);

if (count < LIM)

vals[count] = prev.tv_usec;

count++;

prev = tb;

timersub(&tb, &ta, &tb);

if (tb.tv_sec > total)

break;

}

fprintf(stderr, "%dus actually took %dus\n",

usec, (int)(tb.tv_sec * 1000000 + tb.tv_usec) / count );

for (i = 0; i < count && i < LIM; i++)

fprintf(stdout, "%d\n", vals[i]);

return 0;

}