D 不可中断睡眠 (通常是在IO操作)
R 正在运行或可运行（在运行队列排队中）
S 可中断睡眠 (在等待某事件完成)
T Stopped, either by a job control signal or because it is being traced.
W 正在换页(2.6.内核之前有效)
X 死进程 (should never be seen)
Z 僵尸
BSD风格的
< high-priority (not nice to other users)
N low-priority (nice to other users)
L has pages locked into memory (for real-time and custom IO)
s is a session leader
l is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)
+ is in the foreground process group
