1、struct util_est
/**
* struct util_est - Estimation（估算） utilization of FAIR tasks
* @enqueued: instantaneous（瞬時） estimated utilization of a task/cpu
* @ewma: the Exponential（指數） Weighted Moving Average (EWMA)
* utilization of a task
*
* Support data structure to track an Exponential Weighted Moving Average
* (EWMA) of a FAIR task's utilization. New samples are added to the moving
* average each time a task completes an activation（激活）. Sample's weight is chosen
* so that the EWMA will be relatively insensitive（不敏感） to transient（瞬時） changes to the
* task's workload.
*
* The enqueued attribute has a slightly different meaning for tasks and cpus:
* - task: the task's util_avg at last task dequeue time
* - cfs_rq: the sum of util_est.enqueued for each RUNNABLE task on that CPU
* Thus, the util_est.enqueued of a task represents the contribution on the
* estimated utilization of the CPU where that task is currently enqueued.
*
* Only for tasks we track a moving average of the past(過去的) instantaneous
* estimated utilization. This allows to absorb(吸收) sporadic(零星) drops in utilization
* of an otherwise almost periodic task.
*/
struct util_est {
unsigned int enqueued;入隊列時估算的task的效力
unsigned int ewma;指數加權動態的平均task的效力
#define UTIL_EST_WEIGHT_SHIFT 2
} __attribute__((__aligned__(sizeof(u64))));