task_timeslice()

根据进程p的静态优先级static_prio计算该进程的时间片
(根据下面公式计算时间片)

static  inline unsigned  int  task_timeslice(task_t  * p)
... {
    if (p->static_prio < NICE_TO_PRIO(0))
        return SCALE_PRIO(DEF_TIMESLICE*4, p->static_prio);
    else
        return SCALE_PRIO(DEF_TIMESLICE, p->static_prio);
}

注:(1)
                          +--> (140 - static priority) * 20 
                          |          (static priority < 120)
(task_struct.time_slice)  |        
  base time quantum =     |                                  
(in milliseconds)         |
                          |          (static priority >= 120)
                          +--> (140 - static priority) * 5 

(2)
NICE_TO_PRIO(0) = 120

(3)
#define SCALE_PRIO(x, prio) /
    max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO/2), MIN_TIMESLICE)
--------------------------------------------------------
    max(x * (140 - prio) / (40/2), 5) =
    max(x * (140 - prio) / 20), 5)