Os Memory Management Questions Medium
The role of a page table in virtual memory management is to provide the mapping between virtual addresses used by a process and the physical addresses in the main memory. It acts as a translation mechanism, allowing the operating system to allocate and manage memory resources efficiently.
When a process requests memory, it is assigned a range of virtual addresses that it can use. These virtual addresses are divided into fixed-size units called pages. The page table keeps track of the mapping between these virtual pages and the corresponding physical pages in the main memory.
The page table typically consists of a hierarchical structure, with multiple levels of tables or directories. Each level of the page table provides a level of indirection, allowing for efficient lookup and management of memory mappings. The top-level table, also known as the page directory, contains pointers to the next level of tables, and so on, until the final level contains the actual physical addresses.
When a process accesses a virtual address, the page table is consulted to determine the corresponding physical address. If the mapping is not present in the page table, it triggers a page fault, and the operating system is responsible for handling this exception. The operating system may then allocate a physical page, update the page table, and resume the process.
The page table also plays a crucial role in memory protection and sharing. Each entry in the page table contains additional information, such as access permissions and flags, to control the level of access a process has to a particular page. This allows the operating system to enforce memory protection and prevent unauthorized access.
In summary, the page table is a fundamental component of virtual memory management, providing the necessary mapping between virtual and physical addresses, enabling efficient memory allocation, protection, and sharing.