How to set the process priority in C++

Question

I am working on a program to sort data, and I need to to set the process to priority 31, which I believe is the highest process priority in Windows. I have done some research, but can't figure out how to do it in C++.

Answer 1

The Windows API call SetPriorityClass allows you to change your process priority, see the example in the MSDN documentation, and use REALTIME_PRIORITY_CLASS to set the highest priority:

SetPriorityClass(GetCurrentProcess(), REALTIME_PRIORITY_CLASS)

Caution: if you are asking for true realtime priority, you are going to get it. This is a nuke. The OS will mercilessly prioritize a realtime priority thread, well above even OS-level input processing, disk-cache flushing, and other high-priority time-critical tasks. You can easily lock up your entire system if your realtime thread(s) drain your CPU capacity. Be cautious when doing this, and unless absolutely necessary, consider using high-priority instead. More information

Answer 2

The following function will do the job:

void SetProcessPriority(LPWSTR ProcessName, int Priority)
{
    PROCESSENTRY32 proc32;
    HANDLE hSnap;
    if (hSnap = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0));
    if (hSnap == INVALID_HANDLE_VALUE)
    {

    }
    else
    {
        proc32.dwSize = sizeof(PROCESSENTRY32);
        while ((Process32Next(hSnap, &proc32)) == TRUE)
        {
            if (_wcsicmp(proc32.szExeFile, ProcessName) == 0)
            {
                HANDLE h = OpenProcess(PROCESS_SET_INFORMATION, TRUE, proc32.th32ProcessID);
                SetPriorityClass(h, Priority);
                CloseHandle(h);
            }
        }
        CloseHandle(hSnap);
    }
}

For example, to set the priority of the current process to below normal, use:

SetProcessPriority(GetCurrentProcess(), BELOW_NORMAL_PRIORITY_CLASS)

Answer 3

After (or before) SetPriorityClass, you must set the individual thread priority to achieve the maximum possible. Additionally, another security token is required for realtime priority class, so be sure to grab it (if accessible). SetThreadPriority is the secondary API after SetPriorityClass.