epoll_server

代码如下：

#include <sys/socket.h>#include <sys/epoll.h>#include <netinet/in.h>#include <arpa/inet.h>#include <fcntl.h>#include <unistd.h>#include <stdio.h>#include <pthread.h>#include <errno.h>#define PORT 8888#define MAXFDS 5000#define EVENTSIZE 100#define BUFFER "HTTP/1.1 200 OK/r/nContent-Length: 5/r/nConnection: close/r/nContent-Type: text/html/r/n/r/nHello"int epfd;void *serv_epoll(void *p);void setnonblocking(int fd){    int opts;    opts=fcntl(fd, F_GETFL);    if (opts < 0)    {          fprintf(stderr, "fcntl failed/n");          return;    }    opts = opts | O_NONBLOCK;    if(fcntl(fd, F_SETFL, opts) < 0)    {          fprintf(stderr, "fcntl failed/n");          return;    }    return;}int main(int argc, char *argv[]){    int fd, cfd,opt=1;    struct epoll_event ev;    struct sockaddr_in sin, cin;    socklen_t sin_len = sizeof(struct sockaddr_in);    pthread_t tid;    pthread_attr_t attr;    epfd = epoll_create(MAXFDS);    if ((fd = socket(AF_INET, SOCK_STREAM, 0)) <= 0)    {          fprintf(stderr, "socket failed/n");          return -1;    }    setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (const void*)&opt, sizeof(opt));    memset(&sin, 0, sizeof(struct sockaddr_in));    sin.sin_family = AF_INET;    sin.sin_port = htons((short)(PORT));    sin.sin_addr.s_addr = INADDR_ANY;    if (bind(fd, (struct sockaddr *)&sin, sizeof(sin)) != 0)    {          fprintf(stderr, "bind failed/n");          return -1;    }    if (listen(fd, 32) != 0)    {          fprintf(stderr, "listen failed/n");          return -1;    }    pthread_attr_init(&attr);    pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_DETACHED);    if (pthread_create(&tid, &attr, serv_epoll, NULL) != 0)    {          fprintf(stderr, "pthread_create failed/n");          return -1;    }    while ((cfd = accept(fd, (struct sockaddr *)&cin, &sin_len)) > 0)    {          setnonblocking(cfd);          ev.data.fd = cfd;          ev.events = EPOLLIN | EPOLLET;          epoll_ctl(epfd, EPOLL_CTL_ADD, cfd, &ev);          //printf("connect from %s/n",inet_ntoa(cin.sin_addr));          //printf("cfd=%d/n",cfd);    }    if (fd > 0)          close(fd);    return 0;}void *serv_epoll(void *p){    int i, ret, cfd, nfds;;    struct epoll_event ev,events[EVENTSIZE];    char buffer[512];    while (1)    {          nfds = epoll_wait(epfd, events, EVENTSIZE , -1);          //printf("nfds ........... %d/n",nfds);          for (i=0; i<nfds; i++)          {                if(events[i].events & EPOLLIN)                {                    cfd = events[i].data.fd;                    ret = recv(cfd, buffer, sizeof(buffer),0);                    //printf("read ret..........= %d/n",ret);                    ev.data.fd = cfd;                    ev.events = EPOLLOUT | EPOLLET;                    epoll_ctl(epfd, EPOLL_CTL_MOD, cfd, &ev);                }                else if(events[i].events & EPOLLOUT)                {                    cfd = events[i].data.fd;                    ret = send(cfd, BUFFER, strlen(BUFFER), 0);                    //printf("send ret...........= %d/n", ret);                    ev.data.fd = cfd;                    epoll_ctl(epfd, EPOLL_CTL_DEL, cfd, &ev);                    //shutdown(cfd, 1);                    close(cfd);                }          }    }    return NULL;}

测试结果;
[yangjian2@localhost bin]$ ./ab -c 50 -n 10000 [url]http://202.108.xxx.xxx:8888/[/url]
This is ApacheBench, Version 2.0.41-dev <Revision:1.121.2.12> apache-2.0
Copyright (c) 1996 Adam Twiss, Zeus Technology Ltd, [url]http://www.zeustech.net/[/url]
Copyright (c) 1998-2002 The Apache Software Foundation, [url]http://www.apache.org/[/url]

Benchmarking 202.108.xxx.xxx (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
Completed 7000 requests
Completed 8000 requests
Completed 9000 requests
Finished 10000 requests

Server Software:
Server Hostname: 202.108.xxx.xxx
Server Port: 8888

Document Path: /
Document Length: 5 bytes

Concurrency Level: 50
Time taken for tests: 0.921732 seconds
Complete requests: 10000
Failed requests: 0
Write errors: 0
Total transferred: 872088 bytes
HTML transferred: 50120 bytes
Requests per second: 10849.14 [#/sec] (mean)
Time per request: 4.609 [ms] (mean)
Time per request: 0.092 [ms] (mean, across all concurrent requests)
Transfer rate: 923.26 [Kbytes/sec] received

Connection Times (ms)
min mean[+/-sd] median max
Connect: 1 1 0.9 2 3
Processing: 1 2 0.5 2 4
Waiting: 0 1 0.3 1 3
Total: 4 4 0.2 4 5
WARNING: The median and mean for the initial connection time are not within a normal deviation
These results are probably not that reliable.

Percentage of the requests served within a certain time (ms)
50% 4
66% 4
75% 4
80% 4
90% 4
95% 4
98% 5
99% 5
100% 5 (longest request)

epoll优缺点：
优点：
1.支持一个进程打开大数目的socket描述符。
2.IO效率不随FD数目增加而线性下降。
3.使用mmap加速内核与用户空间的消息传递。
4.内核微调。
epoll底层实现
在调用epoll_create时操作系统会创建一颗红黑树存放socket和一个队列存放就绪事件