Q4计算CPU负荷提供了函数qnx_osstat，可以得到32个优先级的平均负荷cpu_load_。但是这个平均负荷到底是多长时间内的呢？
手册里也写了：
The period over which the cpu_load is averaged is set by the sac utility. The numbers are relative to each other
看了SAC的使用，感觉-i参数比较靠谱：
The Kernel collects statistics on processor activity at each priority level. These statistics are integrated over time. The -i option sets the integration factor for the system. Smaller values average over shorter periods, resulting in a faster response to changes in system activity. Larger values let you monitor average activity over a longer period of time. If you set the integration factor to 0, then statistics won’t be gathered. If you don’t specify the -i option, then the current integration factor will be used. If a node is not gathering statistics, you will be told to set a value for the integration factor. In this case, re-run sac with a nonzero value for the -i option.
最终的问题：SAC的-i参数设置了一个因子（我理解的），那么这个因子乘以的是什么时间间隔呢？即cpu_load是多长时间间隔内的平均负荷？_