redis使用epoll的代码在ae_epoll.c文件中。
epoll_create：redis服务器在启动时，创建事件循环，调用epoll_create方法创建epoll实例。
static int aeApiCreate(aeEventLoop *eventLoop) {aeApiState *state = zmalloc(sizeof(aeApiState));if (!state) return -1;state->events = zmalloc(sizeof(struct epoll_event)*eventLoop->setsize);if (!state->events) {zfree(state);return -1;}state->epfd = epoll_create(1024); /* 1024 is just a hint for the kernel */if (state->epfd == -1) {zfree(state->events);zfree(state);return -1;}eventLoop->apidata = state;return 0; }
epoll_ctl：当有新的客户端连接时，把新的连接描述符注册到epoll实例。
static int aeApiAddEvent(aeEventLoop *eventLoop, int fd, int mask) {aeApiState *state = eventLoop->apidata;struct epoll_event ee = { 0}; /* avoid valgrind warning *//* If the fd was already monitored for some event, we need a MOD* operation. Otherwise we need an ADD operation. */int op = eventLoop->events[fd].mask == AE_NONE ?EPOLL_CTL_ADD : EPOLL_CTL_MOD;ee.events = 0;mask |= eventLoop->events[fd].mask; /* Merge old events */if (mask & AE_READABLE) ee.events |= EPOLLIN;if (mask & AE_WRITABLE) ee.events |= EPOLLOUT;ee.data.fd = fd;if (epoll_ctl(state->epfd,op,fd,&ee) == -1) return -1;return 0; }
epoll_wait：调用epoll_wait获取客户端产生的io事件。
static int aeApiPoll(aeEventLoop *eventLoop, struct timeval *tvp) {aeApiState *state = eventLoop->apidata;int retval, numevents = 0;retval = epoll_wait(state->epfd,state->events,eventLoop->setsize,tvp ? (tvp->tv_sec*1000 + tvp->tv_usec/1000) : -1);if (retval > 0) {int j;numevents = retval;for (j = 0; j < numevents; j++) {int mask = 0;struct epoll_event *e = state->events+j;if (e->events & EPOLLIN) mask |= AE_READABLE;if (e->events & EPOLLOUT) mask |= AE_WRITABLE;if (e->events & EPOLLERR) mask |= AE_WRITABLE;if (e->events & EPOLLHUP) mask |= AE_WRITABLE;eventLoop->fired[j].fd = e->data.fd;eventLoop->fired[j].mask = mask;}}return numevents; }