什么时候两个虚拟地址可以映射到相同的物理地址?

问题描述：

此处是一个操作系统/计算机体系结构问题.我正在阅读有关高速缓存的信息，有关如何对高速缓存进行虚拟索引是减少地址转换时间的一种选择.我遇到了以下问题:

An operating system/computer architecture question here. I was reading about caches, about how virtually indexing the cache is an option to reduce address translation time. I came across the following:

"Virtual cache difficulties include:
    Aliasing
        Two different virtual addresses may have the same physical address."

我想不出什么时候会发生这种情况.自从我的操作系统以来已经有一段时间了，我正在画一个空白.

I can't think of a scenario when this can occur. It's been a while since my O/S days and I'm drawing a blank.

有人可以举个例子吗?谢谢

Could someone provide an example? Thanks

答

两个进程可能具有共享的映射.例如，在Unix中，可执行代码通常映射到执行同一程序的所有进程之间共享的区域中. (实际上，一个单个进程可能具有相同基础内存的多个映射，例如，当mmap是同一文件两次时.)

Two processes might have a shared mapping. E.g., in Unix, executable code is typically mapped into a region shared between all processes that execute the same program. (In fact, a single process might have several mappings of the same underlying memory, e.g. when it mmap's the same file twice.)

什么时候两个虚拟地址可以映射到相同的物理地址?

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