Search results
Results From The WOW.Com Content Network
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 ...
However, if the page size is increased to 32 KiB (2 15 bytes), only 2 17 pages are required. A multi-level paging algorithm can decrease the memory cost of allocating a large page table for each process by further dividing the page table up into smaller tables, effectively paging the page table.
The multilevel page table may keep a few of the smaller page tables to cover just the top and bottom parts of memory and create new ones only when strictly necessary. Now, each of these smaller page tables are linked together by a master page table, effectively creating a tree data structure. There need not be only two levels, but possibly ...
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 ...
The page table, generally stored in main memory, keeps track of where the virtual pages are stored in the physical memory. This method uses two memory accesses (one for the page-table entry, one for the byte) to access a byte. First, the page table is looked up for the frame number.
A pair of a word address and an offset within the word is called a wide address (also known as a fat address or fat pointer). (This should not be confused with other uses of wide addresses for storing other kinds of supplemental data, such as the bounds of an array.) The stored offset may be either a bit offset or a byte offset.
[2] [3] In simple memory subsystems, the word is transferred over the memory data bus, which typically has a width of a word or half-word. In memory subsystems that use caches , the word-sized transfer is the one between the processor and the first level of cache; at lower levels of the memory hierarchy larger transfers (which are a multiple of ...
An access descriptor contains permission bits and a 26-bit object index; the object index is an index into a table of object descriptors, giving an object type, an object length, and a physical address for the object's data, a page table for the object, or the top-level page table for a two-level page table for the object, depending on the ...