这些函数为内核和用户空间之间的内存移动提供了基本功能。

These functions provide the basics for memory movement between the kernel and user-space.

youdao

这使它与缓存操作非常类似，后者是将指令块从内存移动到本地快速缓存中执行。

This makes it very similar to caching operations, where blocks of instructions are moved from memory into a local fast cache memory for execution.

youdao

当经过修改的永久存储分页需要换出(从内存移动到磁盘)的时候，会将它写入到文件系统中。

When a modified permanent storage page needs to be paged out (moved from memory to disk), it is written to a file system.

youdao

So even though we're not literally throwing RAM away, we're not physically moving anything, conceptually, we have to go through memory in this order back to back to back and then undo it.

即使我们没有把内存依次扔掉，我们物理上没有移动任何东西，概念地，我们必须按照顺序经过内存,回到这里然后撤销它。

哈佛公开课 - 计算机科学课程节选