问题
At first I thought there is only one page table for the whole system. But there are actually one page table per process? What is the point of having multiple page table instead of one page table.
I am implementing part of os161
回答1:
A page table usually has a fixed number of entries and therefore describes only a portion of the entire virtual address space. This is why you need multiple of them to cover the entire address space. Now, in many OSes processes have individual (in other words, not shared with others) virtual address spaces, which helps to protect processes from one another. This is another reason for having multiple page tables.
回答2:
Page table translates from virtual to physical page addresses. Since each process has its own virtual address space and usually maps the same virtual address to a different physical address it needs a separate page table. Curiously, multiple processes may map different virtual addresses to the same physical memory. This can be used to implement shared libraries or inter-process communication.
来源：https://stackoverflow.com/questions/8305254/why-one-page-table-per-process