注意！GetThreadPriority的返回值不是系统的优先级值

GetThreadPriority的返回值

Return code/value	Description
THREAD_PRIORITY_ABOVE_NORMAL 1	Priority 1 point above the priority class.
THREAD_PRIORITY_BELOW_NORMAL -1	Priority 1 point below the priority class.
THREAD_PRIORITY_HIGHEST 2	Priority 2 points above the priority class.
THREAD_PRIORITY_IDLE -15	Base priority of 1 for IDLE_PRIORITY_CLASS, BELOW_NORMAL_PRIORITY_CLASS, NORMAL_PRIORITY_CLASS, ABOVE_NORMAL_PRIORITY_CLASS, or HIGH_PRIORITY_CLASSprocesses, and a base priority of 16 forREALTIME_PRIORITY_CLASS processes.
THREAD_PRIORITY_LOWEST -2	Priority 2 points below the priority class.
THREAD_PRIORITY_NORMAL 0	Normal priority for the priority class.
THREAD_PRIORITY_TIME_CRITICAL 15	Base-priority level of 15 for IDLE_PRIORITY_CLASS, BELOW_NORMAL_PRIORITY_CLASS, NORMAL_PRIORITY_CLASS,ABOVE_NORMAL_PRIORITY_CLASS, or HIGH_PRIORITY_CLASSprocesses, and a base-priority level of 31 forREALTIME_PRIORITY_CLASS processes.

系统的优先级值

Process priority class		Thread priority level	Base priority
IDLE_PRIORITY_CLASS		THREAD_PRIORITY_IDLE	1
		THREAD_PRIORITY_LOWEST	2
		THREAD_PRIORITY_BELOW_NORMAL	3
		THREAD_PRIORITY_NORMAL	4
		THREAD_PRIORITY_ABOVE_NORMAL	5
		THREAD_PRIORITY_HIGHEST	6
		THREAD_PRIORITY_TIME_CRITICAL	15
BELOW_NORMAL_PRIORITY_CLASS		THREAD_PRIORITY_IDLE	1
		THREAD_PRIORITY_LOWEST	4
		THREAD_PRIORITY_BELOW_NORMAL	5
		THREAD_PRIORITY_NORMAL	6
		THREAD_PRIORITY_ABOVE_NORMAL	7
		THREAD_PRIORITY_HIGHEST	8
		THREAD_PRIORITY_TIME_CRITICAL	15
NORMAL_PRIORITY_CLASS		THREAD_PRIORITY_IDLE	1
		THREAD_PRIORITY_LOWEST	6
		THREAD_PRIORITY_BELOW_NORMAL	7
		THREAD_PRIORITY_NORMAL	8
		THREAD_PRIORITY_ABOVE_NORMAL	9
		THREAD_PRIORITY_HIGHEST	10
		THREAD_PRIORITY_TIME_CRITICAL	15
ABOVE_NORMAL_PRIORITY_CLASS		THREAD_PRIORITY_IDLE	1
		THREAD_PRIORITY_LOWEST	8
		THREAD_PRIORITY_BELOW_NORMAL	9
		THREAD_PRIORITY_NORMAL	10
		THREAD_PRIORITY_ABOVE_NORMAL	11
		THREAD_PRIORITY_HIGHEST	12
		THREAD_PRIORITY_TIME_CRITICAL	15
HIGH_PRIORITY_CLASS		THREAD_PRIORITY_IDLE	1
		THREAD_PRIORITY_LOWEST	11
		THREAD_PRIORITY_BELOW_NORMAL	12
		THREAD_PRIORITY_NORMAL	13
		THREAD_PRIORITY_ABOVE_NORMAL	14
		THREAD_PRIORITY_HIGHEST	15
		THREAD_PRIORITY_TIME_CRITICAL	15
REALTIME_PRIORITY_CLASS		THREAD_PRIORITY_IDLE	16
		THREAD_PRIORITY_LOWEST	22
		THREAD_PRIORITY_BELOW_NORMAL	23
		THREAD_PRIORITY_NORMAL	24
		THREAD_PRIORITY_ABOVE_NORMAL	25
		THREAD_PRIORITY_HIGHEST	26
		THREAD_PRIORITY_TIME_CRITICAL	31

windows核心编程 5th 184页

Windows并没有提供返回线程优先级的函数。这一遗漏是Microsoft故意的。请记住Microsoft保留了任何时候改变调度算法的权利。我们设计的应用程序不应该了解调度算法具体细节。如果我们始终使用进程优先级类和相对线程优先级，那么我们的应用程序在现在和在操作系统的未来版本都可以运行得很好。

参考资源:

GetThreadPriority function

Scheduling Priorities