对象WMA（虚拟内存区域：）和PTE（页表项）之间有什么区别？

Question

对象WMA（用于运行内核Linux的虚拟内存区： struct vm_area_struct ）和PTE（用于操作MMU的页表项）之间有什么区别，为什么我们需要WMA而没有足够的PTE？

Answer 1

The virtual memory address space of each process is divided into virtual memory areas (VMAs) where all the memory in one VMA is contiguous and shares certain properties such as permissions. For example, a process might have one VMA for its code, one VMA for each type of data, one VMA for each distinct memory mapping (if any), etc.

Each VMA consists of a number of pages, where a page is the unit for moving between main physical memory and backing store.

Each page has an entry in the Page Table, to indicate whether the page is currently in physical memory (in which case it points to the physical memory address of the page) or currently “paged out” on the system's backing storage (in which case it points to the backing storage address of the page copy).

So each VMA has multiple PTEs.

The function of the VMA is to define a contiguous area of virtual memory (contiguous virtual addresses, not contiguous physical addresses) with the correct permissions.

The function of the Page Table is to manage paging between main physical memory and backing store, and to be the communication point between the system/hardware (the MMU) and the OS software.