我在切换到Windows 8后,我的应用程序停止工作了。我花费了几个小时来调试问题,发现IOCP在Windows 8和之前的版本之间表现不同。我提取了必要的代码来演示和复现问题。
SOCKET sListen;
DWORD WINAPI WorkerProc(LPVOID lpParam)
{
ULONG_PTR dwKey;
DWORD dwTrans;
LPOVERLAPPED lpol;
while(true)
{
GetQueuedCompletionStatus((HANDLE)lpParam, &dwTrans, &dwKey, (LPOVERLAPPED*)&lpol, WSA_INFINITE);
printf("dequeued an IO\n");
}
}
DWORD WINAPI StartProc(LPVOID lpParam)
{
WSADATA WsaData;
if (WSAStartup(0x202,&WsaData)!=0) return 1;
sListen = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0, WSA_FLAG_OVERLAPPED);
SOCKADDR_IN si;
ZeroMemory(&si,sizeof(si));
si.sin_family = AF_INET;
si.sin_port = ntohs(1999);
si.sin_addr.S_un.S_addr = INADDR_ANY;
if(bind(sListen, (sockaddr*)&si, sizeof(si)) == SOCKET_ERROR) return 1;
listen(sListen, SOMAXCONN);
HANDLE hCompletion = CreateIoCompletionPort(INVALID_HANDLE_VALUE, 0, 0, 0);
CreateIoCompletionPort((HANDLE)sListen, hCompletion, (DWORD)0, 0);
CreateThread(NULL, 0, WorkerProc, hCompletion, 0, NULL);
return 0;
}
DWORD WINAPI AcceptProc(LPVOID lpParam)
{
DWORD dwBytes;
LPOVERLAPPED pol=(LPOVERLAPPED)malloc(sizeof(OVERLAPPED));
ZeroMemory(pol,sizeof(OVERLAPPED));
SOCKET sClient = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0, WSA_FLAG_OVERLAPPED);
BOOL b = AcceptEx(sListen,
sClient,
malloc ((sizeof(sockaddr_in) + 16) * 2),
0,
sizeof(sockaddr_in) + 16,
sizeof(sockaddr_in) + 16,
&dwBytes,
pol);
if(!b && WSAGetLastError() != WSA_IO_PENDING) return 1;
HANDLE hPipe=CreateNamedPipeA("\\\\.\\pipe\\testpipe",PIPE_ACCESS_DUPLEX,PIPE_TYPE_BYTE | PIPE_READMODE_BYTE | PIPE_WAIT,PIPE_UNLIMITED_INSTANCES,4096,4096,999999999,NULL);
BYTE chBuf[1024];
DWORD cbRead;
CreateFileA("\\\\.\\pipe\\testpipe", GENERIC_READ |GENERIC_WRITE, 0,NULL, OPEN_EXISTING, 0, NULL);
ReadFile(hPipe,chBuf,1024, &cbRead,NULL);
return 0;
}
int main()
{
printf ("Starting server on port 1999...");
WaitForSingleObject(CreateThread(NULL, 0, StartProc, NULL, 0, NULL),INFINITE);
CreateThread(NULL, 0,AcceptProc, NULL, 0, NULL);
printf ("done\n");
Sleep(10000000);
return 0;
}
这个程序监听1999端口,异步接受请求并读取阻塞管道。我在Windows 7、8、XP、2003和2008上测试了这个程序,在"telnet 127.0.0.1 1999"之后,控制台会打印"dequeued an IO\n",但Windows 8除外。
关键点是最初发出异步操作的线程不能在ReadFile中阻塞,否则GetQueuedCompletionStatus将无法在Windows 8上出列该IO,直到ReadFile返回。
我还使用了"scanf"代替读取管道进行测试,结果相同,因为"scanf"最终会调用ReadFile读取控制台。我不知道是否只有ReadFile受到影响,或者可能存在其他功能受到影响。
我能想到的是使用专用线程来发出异步操作,并且所有业务逻辑与该专用线程通信以执行accept/send/recv。但额外的层意味着额外的开销,有没有办法在Windows 8上实现与之前版本相同的性能?