SN-0433 已核对来源，附原文与上下文。
它为每个线程设置不同的优先级。生成线程以 PRIO_MIN 运行。其他线程几乎不占 CPU，以普通优先级运行。
It sets different priorities for each thread. The generate threads run at PRIO_MIN. The other threads rarely take any CPU and run at normal.
#define THREAD_PRIORITY_LOWEST PRIO_MIN
#define THREAD_PRIORITY_BELOW_NORMAL 2
#define THREAD_PRIORITY_NORMAL 0由 Windows 优先级换算来的那些值，大概出自这样一张表：
The priorities converted from Windows priorities were probably from a table like this:
"下表展示了 nice 值与 Win32 优先级之间的映射。Win32 优先级问题的更多信息参见 SetThreadPriority() 的 Win32 文档。
"The following table shows the mapping between nice values and Win32 priorities. Refer to the Win32 documentation for SetThreadPriority() for more information on Win32 priority issues.
nice 值 Win32 优先级
nice value Win32 Priority
-20 到 -16 THREAD_PRIORITY_HIGHEST
-20 to -16 THREAD_PRIORITY_HIGHEST
-15 到 -6 THREAD_PRIORITY_ABOVE_NORMAL
-15 to -6 THREAD_PRIORITY_ABOVE_NORMAL
-5 到 +4 THREAD_PRIORITY_NORMAL
-5 to +4 THREAD_PRIORITY_NORMAL
+5 到 +14 THREAD_PRIORITY_BELOW_NORMAL
+5 to +14 THREAD_PRIORITY_BELOW_NORMAL
+15 到 +19 THREAD_PRIORITY_LOWEST"
+15 to +19 THREAD_PRIORITY_LOWEST"
如果你有更好的取值，欢迎建议。
If you have better values, suggestions welcome.
另外，网上有些建议说 Linux 上应该用 PRIO_PROCESS，因为线程即进程。如果这说法不成立，也许这就解释了为什么整个应用的优先级被意外设置。
Also, there was some advice on the web that PRIO_PROCESS is used on Linux because threads are processes. If that's not true, maybe it accounts for unexpectedly setting the priority of the whole app.
// threads are processes on linux, so PRIO_PROCESS affects just the one thread
// threads are processes on linux, so PRIO_PROCESS affects just the one thread
setpriority(PRIO_PROCESS, getpid(), nPriority);
setpriority(PRIO_PROCESS, getpid(), nPriority);