What is pte in linux

In Linux, PTE is a data structure used to describe the page mapping relationship between virtual memory and physical memory. It contains some fields: 1. Physical page frame number, indicating virtual memory page The address of the mapped physical memory page; 2. Access permission bit, indicating whether the current page is readable, writable, executable and other permission information; 3. Dirty bit, used to mark whether the page has been modified to support the page replacement algorithm ; 4. Sharing bit, indicating whether the page can be shared by multiple processes; 5. Cache bit, used to control the cache policy of the page.

The operating system of this tutorial: Linux5.18.14 system, Dell G3 computer.

In Linux, PTE (Page Table Entry) is a data structure used to describe the page mapping relationship between virtual memory and physical memory. It is an entry in the page table (Page Table), and each virtual memory page corresponds to a PTE.

PTE contains some fields used to record the status of the current virtual memory page and the physical memory address related to it. These fields usually include the following:

• Physical Page Frame Number: Indicates the address of the physical memory page to which the virtual memory page is mapped.

• Access Permission Bits: Indicates whether the current page is readable, writable, executable and other permission information.

• Dirty Bit: used to mark whether the page has been modified to support the page replacement algorithm.

• Shared Bit: Indicates whether the page can be shared by multiple processes.

• Caching Bits: used to control the caching strategy of the page, such as whether it can be cached in the CPU cache.

By using PTE, the operating system can find the corresponding PTE according to the virtual address and obtain the physical memory address from it to implement virtual memory management and access control.

It should be noted that the page table hierarchy in Linux is relatively complex, including multi-level page table structures and corresponding PTEs. The most common is the three-level page table structure, which consists of Page Directory, Page Middle Directory and Page Table. Each level contains the corresponding PTE. This multi-level page table structure can effectively manage a large amount of virtual memory space, and only needs to load part of the page table to save system resources.

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