epoll 惊群效应实测

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#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <sys/epoll.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <fcntl.h>



const int MAX_PROC_NUM = 4;
const int MAX_EVENTS = 128;
const int PORT = 8081;
const int BUF_SIZE = 1024;
const int CLIENT_SIZE = 128;
int g_pids[MAX_PROC_NUM] = {0};

void sig_handler(int signo) {
    int i;
    for (i = 0; i &lt; MAX_PROC_NUM; i++) {
        kill(g_pids[i], SIGKILL);
    }
}

int child_procedure(int listenfd) {
    struct epoll_event ev;
    struct epoll_event events[MAX_EVENTS];
    int epfd = 0;
    int pid = 0;
    char buf[BUF_SIZE];
    int cnt = 0;
    int i = 0;

pid = getpid();

epfd = epoll_create(CLIENT_SIZE + 1);
if (0 == epfd) {
    printf("Create epoll failed\n");
    return -1;
}

ev.events = EPOLLIN | EPOLLET;
ev.data.fd = listenfd;

if (epoll_ctl(epfd, EPOLL_CTL_ADD, listenfd, &amp;ev) &lt; 0) {
    printf("Add ev failed\n");
    return -1;
}   

printf("Epoll init finished, process pid: %d\n", pid);

while (1) {
    cnt = epoll_wait(epfd, events, MAX_EVENTS, 0);
    if (cnt &lt;= 0) {
        continue;
    }

    for (i = 0; i &lt; cnt; i++) {
        if (events[i].data.fd == listenfd) {
            // 新连接请求
            int newfd;
            printf("Process %d receive a connection request\n", pid);
            newfd = accept(listenfd, NULL, 0);
            if(newfd &lt;=0) {
                printf("Process %d accept failed\n", pid);
                continue;
            }
            fcntl(newfd, F_SETFL, fcntl(newfd, F_GETFD, 0)|O_NONBLOCK);
            ev.events = EPOLLIN | EPOLLET;
            ev.data.fd = newfd;
            epoll_ctl(epfd, EPOLL_CTL_ADD, newfd, &amp;ev);
    
        } else {
            int n = read(events[i].data.fd, buf, 1024);
            printf("Process %d receive a msg, length %d\n", pid, n);
            if (n != 0) {
                write(events[i].data.fd, buf, n);
            }
            close(events[i].data.fd);
            epoll_ctl(epfd, EPOLL_CTL_DEL, events[i].data.fd, NULL);
        }
    
    }

}
return 0;

}

int main()
{
    int listenfd = 0;
    int cnt = 0;
    int i = 0;
    struct sockaddr_in servaddr;

    // signal(SIGINT, sig_handler);
    // signal(SIGKILL, sig_handler);
    
    listenfd = socket(AF_INET, SOCK_STREAM, 0);
    
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(PORT);
    
    fcntl(listenfd, F_SETFL, fcntl(listenfd, F_GETFD, 0)|O_NONBLOCK);
    
    if (bind(listenfd, (struct sockaddr *) &amp;servaddr, sizeof(struct sockaddr)) == -1) {
        printf("bind error\n");
        return -1;
    }
    
    if (listen(listenfd, CLIENT_SIZE) == -1) {
        printf("Listen failed\n");
        return -1;
    }
    
    for (i = 0; i &lt; MAX_PROC_NUM; i++) {
        g_pids[i] = fork();
        if (0 == g_pids[i]) {
            // 子进程
            break;
        }
    }
    
    if (i == MAX_PROC_NUM) {
        // 注册信号，父进程退出，子进程一起kill掉
        signal(SIGINT, sig_handler);
        signal(SIGKILL, sig_handler);
    
        // 父进程，阻塞
        while(1) {
            sleep(100);
        }
    } else {
        // 子进程，进入子进程流程
        return child_procedure(listenfd);
    }
    
    return 0;

}

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Epoll init finished, process pid: 20628
Epoll init finished, process pid: 20629
Epoll init finished, process pid: 20630
Epoll init finished, process pid: 20631
Process 20630 receive a connection request
Process 20631 receive a connection request
Process 20628 receive a connection request
Process 20629 receive a connection request
Process 20630 receive a msg, length 169
Process 20631 accept failed
Process 20628 accept failed
Process 20629 accept failed