GetPriorityClass
The GetPriorityClass
function returns 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.
DWORD GetPriorityClass(
|
HANDLE hProcess |
// handle to the
process |
|
); |
|
Parameters
hProcess
Identifies
the process.
Windows
NT: The handle must have
PROCESS_QUERY_INFORMATION access. For more information, see Process Objects.
Return Values
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:
|
Priority |
Meaning |
|
HIGH_PRIORITY_CLASS |
Indicates a
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 Windows
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 |
Indicates a
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 |
Indicates a
normal process with no special scheduling needs. |
|
REALTIME_PRIORITY_CLASS |
Indicates a
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 the SetPriorityClass function.
See Also