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Some operating systems periodically look for pages that have not been recently referenced and then free the page frame and add it to the free page queue, a process known as "page stealing". Some operating systems [e] support page reclamation; if a program commits a page fault by referencing a page that was stolen, the operating system detects ...
The page table is set up by the computer's operating system, and may be read and written during the virtual address translation process by the memory management unit or by low-level system software or firmware.
For a single-level page table, addresses are broken down into a set of bits to index the page table and remaining bits that pass through to the physical address without modification, indexing a byte within the page. For a two-level page table, addresses are borken down into a set of bits to index the root level of the tree, a set of bits to ...
Similarly, a page frame is the smallest fixed-length contiguous block of physical memory into which memory pages are mapped by the operating system. [ 1 ] [ 2 ] [ 3 ] A transfer of pages between main memory and an auxiliary store, such as a hard disk drive , is referred to as paging or swapping.
The operating system then loads the information from that page table entry into the TLB and restarts the program from the instruction that caused the TLB miss. As with hardware TLB management, if the OS finds no valid translation in the page tables, a page fault has occurred, and the OS must handle it accordingly.
In protected mode with paging enabled (bit 31, PG, of control register CR0 is set), but without PAE, x86 processors use a two-level page translation scheme. Control register CR3 holds the page-aligned physical address of a single 4 KB long page directory.
This increases the importance of caching values from intermediate levels of the host and guest page tables. It is also helpful to use large pages in the host page tables to reduce the number of levels (e.g., in x86-64, using 2 MB pages removes one level in the page table). Since memory is typically allocated to virtual machines at coarse ...
Pages in the page cache modified after being brought in are called dirty pages. [5] Since non-dirty pages in the page cache have identical copies in secondary storage (e.g. hard disk drive or solid-state drive), discarding and reusing their space is much quicker than paging out application memory, and is often preferred over flushing the dirty pages into secondary storage and reusing their space.