參考《linux高性能服務器編程》
LINUX下處理多個連接時候,僅僅使用多線程和原始socket函數,效率十分低下
於是就出現了selelct poll epoll等IO複用函數。
這裏討論性能最優的epoll IO複用
用戶將需要關注的socket連接使用IO複用函數放進一個事件表中,每當事件表中有一個或者多個SOCKET連接出現讀寫請求時候,則進行處理
事件表使用一個額外的文件描述符來標識。文件描述符使用 epoll_create函數創建
#inlclude <sys/epoll.h>
int epoll_create(int size); size參數目前不起作用
操作事件表使用epoll_ctl函數進行控制
操作類型有以下3中
EPOLL_CTL_ADD EPOLL_CTL_MOD EPOLL_CTL_DEL
在一段超時時間內等待事件表上的事件 使用epoll_wait();
函數範例如下:
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|
#include
<sys/types.h> #include
<sys/socket.h> #include
<netinet/in.h> #include
<arpa/inet.h> #include
<assert.h> #include
<stdio.h> #include
<unistd.h> #include
<errno.h> #include
<string.h> #include
<fcntl.h> #include
<stdlib.h> #include
<sys/epoll.h> #include
<pthread.h> #define
MAX_EVENT_NUMBER 1024 #define
BUFFER_SIZE 10 int setnonblocking( int fd
) { int old_option
= fcntl( fd, F_GETFL ); int new_option
= old_option | O_NONBLOCK; fcntl(
fd, F_SETFL, new_option ); return old_option; } void addfd( int epollfd, int fd, bool enable_et
) { epoll_event event ; event .data.fd
= fd; event .events
= EPOLLIN; if (
enable_et ) { event .events
|= EPOLLET; } epoll_ctl(
epollfd, EPOLL_CTL_ADD, fd, & event ); setnonblocking(
fd ); } void et(
epoll_event* events, int number, int epollfd, int listenfd
) { char buf[
BUFFER_SIZE ]; for ( int i
= 0; i < number; i++ ) { int sockfd
= events[i].data.fd; if (
sockfd == listenfd ) { struct sockaddr_in
client_address; socklen_t
client_addrlength = sizeof (
client_address ); int connfd
= accept( listenfd, ( struct sockaddr*
)&client_address, &client_addrlength ); addfd(
epollfd, connfd, true ); } else if (
events[i].events & EPOLLIN ) { printf( "event
trigger once\n" ); while (
1 ) { memset(
buf, '\0' ,
BUFFER_SIZE ); int ret
= recv( sockfd, buf, BUFFER_SIZE-1, 0 ); if (
ret < 0 ) { if (
( errno == EAGAIN ) || ( errno == EWOULDBLOCK ) ) { printf( "read
later\n" ); break ; } close(
sockfd ); break ; } else if (
ret == 0 ) { close(
sockfd ); } else { printf( "get
%d bytes of content: %s\n" ,
ret, buf ); } } } else { printf( "something
else happened \n" ); } } } int main( int argc, char *
argv[] ) { if (
argc <= 2 ) { printf( "usage:
%s ip_address port_number\n" ,
basename( argv[0] ) ); return 1; } const char *
ip = argv[1]; int port
= atoi( argv[2] ); int ret
= 0; struct sockaddr_in
address; bzero(
&address, sizeof (
address ) ); address.sin_family
= AF_INET; inet_pton(
AF_INET, ip, &address.sin_addr ); address.sin_port
= htons( port ); int listenfd
= socket( PF_INET, SOCK_STREAM, 0 ); assert(
listenfd >= 0 ); ret
= bind( listenfd, ( struct sockaddr*
)&address, sizeof (
address ) ); assert(
ret != -1 ); ret
= listen( listenfd, 5 ); assert(
ret != -1 ); epoll_event
events[ MAX_EVENT_NUMBER ]; int epollfd
= epoll_create( 5 ); assert(
epollfd != -1 ); addfd(
epollfd, listenfd, true ); while (
1 ) { int ret
= epoll_wait( epollfd, events, MAX_EVENT_NUMBER, -1 ); if (
ret < 0 ) { printf( "epoll
failure\n" ); break ; } et(
events, ret, epollfd, listenfd ); } close(
listenfd ); return 0; } |
在嘗試一個多線程代碼;
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|
#include
<sys/types.h> #include
<sys/socket.h> #include
<netinet/in.h> #include
<arpa/inet.h> #include
<assert.h> #include
<stdio.h> #include
<unistd.h> #include
<errno.h> #include
<string.h> #include
<fcntl.h> #include
<stdlib.h> #include
<sys/epoll.h> #include
<pthread.h> #define
MAX_EVENT_NUMBER 1024 #define
BUFFER_SIZE 10 struct fds { int epollfd; int sockfd; }; void *
worker( void *
arg ) { int sockfd
= ( (fds*)arg )->sockfd; int epollfd
= ( (fds*)arg )->epollfd; printf( "start
new thread to receive data on fd: %d\n" ,
sockfd ); char buf[
BUFFER_SIZE ]; memset(
buf, '\0' ,
BUFFER_SIZE ); while (
1 ) { int ret
= recv( sockfd, buf, BUFFER_SIZE-1, 0 ); if (
ret == 0 ) { close(
sockfd ); printf( "foreiner
closed the connection\n" ); break ; } else if (
ret < 0 ) { if (
errno == EAGAIN ) { //
reset_oneshot( epollfd, sockfd ); printf( "read
later\n" ); break ; } } else { printf( "get
content: %s\n" ,
buf ); sleep(
5 ); } } printf( "end
thread receiving data on fd: %d\n" ,
sockfd ); } int setnonblocking( int fd) { int old_option
= fcntl(fd,F_GETFL); int new_option
= old_option | O_NONBLOCK; fcntl(fd,F_SETFL,new_option); return old_option; } void addfd( int epollfd, int fd, bool enable_et) { epoll_event event ; event .data.fd
= fd; event .events
= EPOLLIN; if (enable_et){ event .events
|= EPOLLET; } epoll_ctl(epollfd,EPOLL_CTL_ADD,fd,& event ); setnonblocking(fd); } void et(epoll_event*
events, int number, int epollfd, int listenfd){ char buf[BUFFER_SIZE]; for ( int i
= 0; i < number;i++){ int sockfd
= events[i].data.fd; if (sockfd
== listenfd){ struct sockaddr_in
client_address; socklen_t
client_addrlength = sizeof (client_address); int connfd
= accept(listenfd,( struct sockaddr*)&client_address,&client_addrlength); addfd(epollfd,connfd, true ); } else if (events[i].events
& EPOLLIN){ /* printf("event
trigger once\n"); while(1){ memset(buf,'\0',BUFFER_SIZE); int
ret = recv(sockfd,buf,BUFFER_SIZE-1,0); if(ret
< 0){ if((errno
== EAGAIN) || (errno == EWOULDBLOCK)){ printf("read
later\n"); break; } close(sockfd); break; }else
if(ret == 0){ close(sockfd); }else{ printf("get
%d bytes of content: %s \n",ret,buf); } }*/ pthread_t
thread; fds
fds_for_new_worker; fds_for_new_worker.epollfd
= epollfd; fds_for_new_worker.sockfd
= sockfd; pthread_create(
&thread, NULL, worker, ( void *
)&fds_for_new_worker ); } else { printf( "something
else happened \n" ); } } } int main() { int ret
= 0; struct sockaddr_in
address; bzero(&address, sizeof (address)); address.sin_family
= AF_INET; inet_pton(AF_INET, "127.0.0.1" ,&address.sin_addr); address.sin_port
= htons(1134); int listenfd
= socket(AF_INET,SOCK_STREAM,0); assert(listenfd
>= 0); ret
= bind(listenfd,( struct sockaddr*)&address, sizeof (address)); assert(ret
!= -1); ret
= listen(listenfd,5); assert(ret
!= -1); epoll_event
events[MAX_EVENT_NUMBER]; int epollfd
= epoll_create(5); assert(epollfd
!= -1); addfd(epollfd,listenfd, true ); while (1){ int ret
= epoll_wait(epollfd,events,MAX_EVENT_NUMBER,-1); if (ret
< 0){ printf( "epoll
failure\n" ); break ; } et(events,ret,epollfd,listenfd); } close(listenfd); return 0; } |
多線程版本中 如果我們 連續多次輸入會出現一個問題
如果我們連續多次在telnet的客戶端輸入
服務端會開啓多個線程 接受這個socket的輸入
顯示如下:
fd: 5, sockfdget content: dfdsf
...
start new thread to receive data on fd: 5
fd: 5, sockfdget content: sd
...
start new thread to receive data on fd: 5
fd: 5, sockfdget content: sd
...
start new thread to receive data on fd: 5
fd: 5, sockfdget content: sd
...
start new thread to receive data on fd: 5
fd: 5, sockfdget content: sd
...
start new thread to receive data on fd: 5
fd: 5, sockfdget content: sd
...
start new thread to receive data on fd: 5
fd: 5, sockfdget content: sd
如果多個線程同時操作一個socket 可能出現各種意外情況
那麼我們就需要設置socket的EPOLLONESHOT標誌
對於連續操作,操作系統最多觸發該socket上一次讀寫異常事件。
代碼如下:
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#include
<sys/types.h> #include
<sys/socket.h> #include
<netinet/in.h> #include
<arpa/inet.h> #include
<assert.h> #include
<stdio.h> #include
<unistd.h> #include
<errno.h> #include
<string.h> #include
<fcntl.h> #include
<stdlib.h> #include
<sys/epoll.h> #include
<pthread.h> #define
MAX_EVENT_NUMBER 1024 #define
BUFFER_SIZE 10 struct fds { int epollfd; int sockfd; }; void reset_oneshot( int epollfd, int fd
) { epoll_event event ; event .data.fd
= fd; event .events
= EPOLLIN | EPOLLET | EPOLLONESHOT; epoll_ctl(
epollfd, EPOLL_CTL_MOD, fd, & event ); } void *
worker( void *
arg ) { int sockfd
= ( (fds*)arg )->sockfd; int epollfd
= ( (fds*)arg )->epollfd; printf( "start
new thread to receive data on fd: %d\n" ,
sockfd ); char buf[
BUFFER_SIZE ]; memset(
buf, '\0' ,
BUFFER_SIZE ); while (
1 ) { int ret
= recv( sockfd, buf, BUFFER_SIZE-1, 0 ); if (
ret == 0 ) { close(
sockfd ); printf( "foreiner
closed the connection\n" ); break ; } else if (
ret < 0 ) { if (
errno == EAGAIN ) { reset_oneshot(
epollfd, sockfd ); printf( "read
later\n" ); break ; } } else { printf( "get
content: %s\n" ,
buf ); sleep(
5 ); } } printf( "end
thread receiving data on fd: %d\n" ,
sockfd ); } int setnonblocking( int fd) { int old_option
= fcntl(fd,F_GETFL); int new_option
= old_option | O_NONBLOCK; fcntl(fd,F_SETFL,new_option); return old_option; } void addfd( int epollfd, int fd, bool setOneShot) { epoll_event event ; event .data.fd
= fd; event .events
= EPOLLIN; event .events
|= EPOLLET; if (setOneShot) event .events
|= EPOLLONESHOT; epoll_ctl(epollfd,EPOLL_CTL_ADD,fd,& event ); setnonblocking(fd); } void et(epoll_event*
events, int number, int epollfd, int listenfd){ char buf[BUFFER_SIZE]; for ( int i
= 0; i < number;i++){ int sockfd
= events[i].data.fd; if (sockfd
== listenfd){ struct sockaddr_in
client_address; socklen_t
client_addrlength = sizeof (client_address); int connfd
= accept(listenfd,( struct sockaddr*)&client_address,&client_addrlength); addfd(epollfd,connfd, true ); } else if (events[i].events
& EPOLLIN){ /* printf("event
trigger once\n"); while(1){ memset(buf,'\0',BUFFER_SIZE); int
ret = recv(sockfd,buf,BUFFER_SIZE-1,0); if(ret
< 0){ if((errno
== EAGAIN) || (errno == EWOULDBLOCK)){ printf("read
later\n"); break; } close(sockfd); break; }else
if(ret == 0){ close(sockfd); }else{ printf("get
%d bytes of content: %s \n",ret,buf); } }*/ pthread_t
thread; fds
fds_for_new_worker; fds_for_new_worker.epollfd
= epollfd; fds_for_new_worker.sockfd
= sockfd; pthread_create(
&thread, NULL, worker, ( void *
)&fds_for_new_worker ); } else { printf( "something
else happened \n" ); } } } int main() { int ret
= 0; struct sockaddr_in
address; bzero(&address, sizeof (address)); address.sin_family
= AF_INET; inet_pton(AF_INET, "127.0.0.1" ,&address.sin_addr); address.sin_port
= htons(1134); int listenfd
= socket(AF_INET,SOCK_STREAM,0); assert(listenfd
>= 0); ret
= bind(listenfd,( struct sockaddr*)&address, sizeof (address)); assert(ret
!= -1); ret
= listen(listenfd,5); assert(ret
!= -1); epoll_event
events[MAX_EVENT_NUMBER]; int epollfd
= epoll_create(5); assert(epollfd
!= -1); addfd(epollfd,listenfd, false ); while (1){ int ret
= epoll_wait(epollfd,events,MAX_EVENT_NUMBER,-1); if (ret
< 0){ printf( "epoll
failure\n" ); break ; } et(events,ret,epollfd,listenfd); } close(listenfd); return 0; } |
輸入
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
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sdfufghbskdjhkbaskjhbkjlsadvfblkajwsvdfbljkashdbkfjhasdfhasjkhD
輸出
start new thread to receive data on fd: 5
get content: 1
get content: 2
3
4
get content: 5
sdfufg
get content: hbskdjhkb
get content: askjhbkjl
get content: sadvfblka
get content: jwsvdfblj
get content: kashdbkfj
get content: hasdfhasj
get content: khD
hasj
read later
end thread receiving data on fd: 5