select-poll和epoll多路复用(事件驱动)技术

linux内核集成了select,poll和epoll三种NIO多路复用技术(多路复用使用事件驱动模型作为编程范式),多路复用技术可以一个进程同时监视多个文件描述符，在大并发条件下可以提高线程利用率，减少线程资源浪费。

¶select

¶原理解析

¶函数解析

/* According to POSIX.1-2001, POSIX.1-2008 */
#include <sys/select.h>
/* According to earlier standards */
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout);
void FD_CLR(int fd, fd_set *set);
int  FD_ISSET(int fd, fd_set *set);
void FD_SET(int fd, fd_set *set);
void FD_ZERO(fd_set *set);

#include <sys/select.h>

/*   
    Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
        pselect(): _POSIX_C_SOURCE >= 200112L
*/
int pselect(int nfds, fd_set *readfds, fd_set *writefds,
                   fd_set *exceptfds, const struct timespec *timeout,
                   const sigset_t *sigmask);

¶实际运用

¶poll

¶原理解析

¶函数解析

#include <poll.h>

int poll(struct pollfd *fds, nfds_t nfds, int timeout);

/* See feature_test_macros(7) */
#define _GNU_SOURCE
#include <signal.h>
#include <poll.h>

int ppoll(struct pollfd *fds, nfds_t nfds, const struct timespec *tmo_p, const sigset_t *sigmask);

¶实际运用

¶epoll

¶原理解析

¶函数解析

#include <sys/epoll.h>
int epoll_create(int size);
int epoll_create1(int flags);
int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);
int epoll_wait(int epfd, struct epoll_event *events, int maxevents, int timeout);
int epoll_pwait(int epfd, struct epoll_event *events, int maxevents, int timeout, const sigset_t *sigmask);

¶实际运用