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Win32 Programming

Where are we?. Last topic: I/O Completion PortsRemind me what we did last class

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Win32 Programming

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    1. Win32 Programming Lesson 27: I/O Completion Ports OUCH

    2. Where are we? Last topic: I/O Completion Ports Remind me what we did last class

    3. Threads (again) Concurrent model where a thread is created to handle the request Leverages thread pooling But it is *very* gnarly

    4. CreateIoCompletionPort HANDLE CreateIoCompletionPort( HANDLE hFile, HANDLE hExistingCompletionPort, ULONG_PTR CompletionKey, DWORD dwNumberOfConcurrentThreads); Pretty confusing, as it does two things

    5. Step 1 HANDLE CreateIoCompletionPort( INVALID_HANDLE_VALUE, NULL, 0, dwNumberOfConcurrentThreads); Creates a new port with dwNumberOfConcurrentThreads (max) What do you notice missing from typical Kernel Object calls?

    6. Step 2 Associate a Device with this port CreateIoCompletionPort( hDevice, hCompletionPort, dwCompletionKey, 0); Next, create 2*CPU threads

    7. Per Thread Wait for requests, putting yourself to sleep in the process BOOL GetQueuedCompletionStatus( HANDLE hCompletionPort, PDWORD pdwNumberOfBytesTransferred, PULONG_PTR pCompletionKey, OVERLAPPED ** ppOverlapped, DWORD dwMilliseconds); Which port are we monitoring? How long to sleep for?

    8. Example DWORD dwNumBytes; ULONG_PTR CompletionKey; OVERLAPPED * pOverlapped; BOOL bOk = GetQueuedCompletionStatus(hIOCP, &dwNumBytes, &CompletionKey, &pOverlapped, 1000); DWORD dwError = GetLastError; if (bOk) { // IO Request OK } else { if (pOverlapped !=NULL) { // We failed } else { if (dwError == WAIT_TIMEOUT) { // We timed out } else { // Bad call to fn } } }

    9. Note IO Completion Requests are FIFO (why?) Thread awakenings are LIFO (why?) Vista allows you to retrieve multiple requests at once (why is this helpful?) GetQueuedCompletionStatusEx(); And now we get to the point How this works when a thread goes to sleep

    10. Dont Need a Real Completion BOOL PostQueuedCompletionStatus( HANDLE hCompletionPort, DWORD dwNumBytes, ULONG_PTR CompletionKey, OVERLAPPED* pOverlapped); Very neat way to do this and has lots of other uses Vista: CloseHandle (hCompletionPort) wakes all threads and returns FALSE with ERROR_INVALID_HANDLE

    11. Congratulations YOU HAVE COMPLETED ALL YOUR NEW MATERIAL Every single person who stuck with me this class has done well!

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