t-poller.c

/*gcc -o t-poller t-poller.c -lpthread*/#include <stdio.h>#include <stdlib.h>#include <string.h>
#include <unistd.h>
#include <poll.h>
#include <pthread.h>
#include <sys/time.h>
#include <sys/resource.h>

#define THREADS 1000
#define ITERATIONS 1000
void * child(void * ptr)
{
    struct pollfd pfd;
    struct rusage ru1, ru2;
    int diff, total;
    int fd = *(int*)ptr;

    total = 0;

    memset(&pfd, 0, sizeof(pfd));
    pfd.fd = fd;
    pfd.events = 0;
    while (write(fd, "foo\n", 4) == 4) {
        getrusage(RUSAGE_SELF, &ru1);
        if (poll(&pfd, 1, 100) != 0)
            break;
        getrusage(RUSAGE_SELF, &ru2);

        diff = ru2.ru_nvcsw - ru1.ru_nvcsw;        if (diff > 2) {
            total += diff;
            printf("volcs for poll() = %d\n", diff);
        }

    }
    printf("%d exited. total %d\n", (int)getpid(), total);
    fprintf(stderr, "%d\n", total);

    return (void *)NULL;

}

int main(void)
{
    struct pollfd pfds[2];
    int i, iterations, fd[2];
    char buf[1024];
    pthread_t threads[THREADS];

    iterations = 0;

    pipe(fd);
    for (i = 0; i < THREADS; i++) {
        pthread_create( &threads[i], NULL, child, (void *)&fd[1]);
    }


    memset(pfds, 0, sizeof(pfds));
    pfds[0].fd = 0;
    pfds[0].events = POLLIN;
    pfds[1].fd = fd[0];
    pfds[1].events = POLLIN;
    while (poll(pfds, 2, -1) > 0) {
        if (pfds[0].revents != 0)
            break;

        if (iterations >= ITERATIONS)
            break;

        if (pfds[1].revents != 0)
            read(fd[0], buf, sizeof(buf));
          
        iterations++;
    }     
         
    close(fd[0]);
    close(fd[1]);
             
    for (i = 0; i < THREADS; i++) {
        pthread_join( threads[i], NULL);
    }
    
    printf("done\n"); 
    return 1;
}