进程状态说明

关于不可中断的休眠的解释
https://eklitzke.org/uninterruptible-sleep
https://lwn.net/Articles/288056/

进程状态代码：下面是s, stat 和 state 输出的限定词 specifiers (表头"STAT" or "S")：
     D    uninterruptible sleep (usually IO) 、不可中断休眠，一般是 IO操作
     I    Idle kernel thread，空闲内核线程
     R    running or runnable (on run queue)，正在运行，或者可以运行（已经在可运行队列里了）
     S    interruptible sleep (waiting for an event to complete)，可被打断的休眠（正在等待一个事件的结束）
     T    stopped by job control signal ，job控制信号中止的线程
     t    stopped by debugger during the tracing；跟踪器停止的进程
     W    paging (not valid since the 2.6.xx kernel)   无效状态
     X    dead (should never be seen) 无效状态
     Z    defunct ("zombie") process, terminated but not reaped by its parent，已经终结，但是未被收集的进程

For BSD formats and when the stat keyword is used, additional characters may be displayed:
               <    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