GetPriorityClass function

Retrieves the priority class for the specified process. This value, together with the priority value of each thread of the process, determines each thread's base priority level.

Syntax

DWORD GetPriorityClass(
  HANDLE hProcess
);

Parameters

hProcess

A handle to the process.

The handle must have the PROCESS_QUERY_INFORMATION or PROCESS_QUERY_LIMITED_INFORMATION access right. For more information, see Process Security and Access Rights.

Windows Server 2003 and Windows XP:  The handle must have the PROCESS_QUERY_INFORMATION access right.

Return Value

If the function succeeds, the return value is the priority class of the specified process.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

The process's priority class is one of the following values.

Return code/value Description
ABOVE_NORMAL_PRIORITY_CLASS
0x00008000
Process that has priority above NORMAL_PRIORITY_CLASS but below HIGH_PRIORITY_CLASS.
BELOW_NORMAL_PRIORITY_CLASS
0x00004000
Process that has priority above IDLE_PRIORITY_CLASS but below NORMAL_PRIORITY_CLASS.
HIGH_PRIORITY_CLASS
0x00000080
Process that performs time-critical tasks that must be executed immediately for it to run correctly. The threads of a high-priority class process preempt the threads of normal or idle priority class processes. An example is the Task List, which must respond quickly when called by the user, regardless of the load on the operating system. Use extreme care when using the high-priority class, because a high-priority class CPU-bound application can use nearly all available cycles.
IDLE_PRIORITY_CLASS
0x00000040
Process whose threads run only when the system is idle and are preempted by the threads of any process running in a higher priority class. An example is a screen saver. The idle priority class is inherited by child processes.
NORMAL_PRIORITY_CLASS
0x00000020
Process with no special scheduling needs.
REALTIME_PRIORITY_CLASS
0x00000100
Process that has the highest possible priority. The threads of a real-time priority class process preempt the threads of all other processes, including operating system processes performing important tasks. For example, a real-time process that executes for more than a very brief interval can cause disk caches not to flush or cause the mouse to be unresponsive.

Remarks

Every thread has a base priority level determined by the thread's priority value and the priority class of its process. The operating system uses the base priority level of all executable threads to determine which thread gets the next slice of CPU time. Threads are scheduled in a round-robin fashion at each priority level, and only when there are no executable threads at a higher level will scheduling of threads at a lower level take place.

For a table that shows the base priority levels for each combination of priority class and thread priority value, see Scheduling Priorities.

Priority class is maintained by the executive, so all processes have a priority class that can be queried.

Examples

For an example, see Taking a Snapshot and Viewing Processes.

Requirements

   
Windows version Windows XP [desktop apps | UWP apps] Windows Server 2003 [desktop apps | UWP apps]
Target Platform Windows
Header processthreadsapi.h (include Windows Server 2003, Windows Vista, Windows 7, Windows Server 2008 Windows Server 2008 R2, Windows.h)
Library Kernel32.lib
DLL Kernel32.dll

See Also

GetThreadPriority

Process and Thread Functions

Processes

Scheduling Priorities

SetPriorityClass

SetThreadPriority