ULONG WINAPI workThread(HANDLE hIOCP)
{
    ULONG dwBytes;
    ULONG_PTR Key;
    OVERLAPPED* Irp;
    while(GetQueuedCompletionStatus(hIOCP, &dwBytes, &Key, &Irp, INFINITE))
    {
        DbgPrint("%x.%u>%p %p %x\n", GetCurrentThreadId(), GetTickCount(), Key, Irp, dwBytes);

        if (Irp)
        {
            delete Irp;
            ULONG64 t = GetTickCount64() + 4000;// wait 4 sec
            do
            {
            } while (GetTickCount64() < t);
        }
        else{
            break;
        }
    }
    return 0;
}

ULONG StartThreads(HANDLE* phThreads, ULONG n, HANDLE hIOCP)
{
    ULONG m = 0;

    do
    {
        if (HANDLE hThread = CreateThread(0, 0x1000, workThread, hIOCP, 0, 0))
        {
            m++;
            *phThreads++ = hThread;
        }
    } while (--n);

    return m;
}

void testIOP()
{
    HANDLE hThreads[2], *phThreads;

    if (HANDLE hIOCP = CreateIoCompletionPort(INVALID_HANDLE_VALUE, 0, 0, 1))
    {
        int i = 4;
        do
        {
            if (OVERLAPPED* Irp = new OVERLAPPED)
            {
                if (!PostQueuedCompletionStatus(hIOCP, i, i, Irp))
                {
                    delete Irp;
                }
            }
        } while (--i);

        PostQueuedCompletionStatus(hIOCP, 1, 1, 0);
        PostQueuedCompletionStatus(hIOCP, 2, 2, 0);

        if (ULONG m = StartThreads(hThreads, RTL_NUMBER_OF(hThreads), hIOCP))
        {
            ULONGLONG t = GetTickCount64();

            WaitForMultipleObjects(m, hThreads, true, INFINITE);

            t = GetTickCount64() - t;

            DbgPrint("%I64u.%u\n", t / 1000, t % 1000);

            phThreads = hThreads + m;

            do
            {
                CloseHandle(*--phThreads);
            } while (--m);
        }

        CloseHandle(hIOCP);
    }
}
f1c.24551937>0000000000000004 000001F939E3E290 4
f1c.24555937>0000000000000003 000001F939E3E150 3
f1c.24559937>0000000000000002 000001F939E36460 2
f1c.24563937>0000000000000001 000001F939E3A6D0 1
f1c.24567937>0000000000000001 0000000000000000 1
The thread 'Win64 Thread' (0xf1c) has exited with code 0 (0x0).
e50.24567937>0000000000000002 0000000000000000 2
The thread 'Win64 Thread' (0xe50) has exited with code 0 (0x0).
16.0