现代计算机的存储系统变得越来越复杂，它是由多级高速缓存、内存和磁盘组成一个层次结构，指令也不再是以常数时间顺序执行。
The memory system of modern computer are becoming increasingly sophisticated , which is a hierarchy consisting of multilevel caches 、 main memory and disk , also instructions are not executed sequentially and in constant time .
多级高速缓存