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If it is a TLB miss, then the CPU checks the page table for the page table entry. If the present bit is set, then the page is in main memory, and the processor can retrieve the frame number from the page-table entry to form the physical address. [6] The processor also updates the TLB to include the new page-table entry.
Unlike a true page table, it is not necessarily able to hold all current mappings. The operating system must be prepared to handle misses, just as it would with a MIPS-style software-filled TLB. The IPT combines a page table and a frame table into one data structure. At its core is a fixed-size table with the number of rows equal to the number ...
The TLB is of limited size, and when it cannot satisfy a given request (a TLB miss) the page tables must be searched manually (either in hardware or software, depending on the architecture) for the correct mapping. Larger page sizes mean that a TLB cache of the same size can keep track of larger amounts of memory, which avoids the costly TLB ...
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 granularity, using large pages for guest-physical translation is an obvious optimization, reducing the depth of ...
Intel 5-level paging, referred to simply as 5-level paging in Intel documents, is a processor extension for the x86-64 line of processors. [1]: 11 It extends the size of virtual addresses from 48 bits to 57 bits by adding an additional level to x86-64's multilevel page tables, increasing the addressable virtual memory from 256 TiB to 128 PiB.
Load the required data into the available page frame. Update the page table to refer to the new page frame. Return control to the program, transparently retrying the instruction that caused the page fault. When all page frames are in use, the operating system must select a page frame to reuse for the page the program now needs.
Supporting 64 bit addresses in the page-table is a significant change as this enables two changes to the processor addressing. Firstly, the page table walker, which uses physical addresses to access the page table and directory, can now access physical addresses greater than the 32-bit physical addresses supported in systems without PAE.
This is because aligning a page on a page-sized boundary lets the hardware map a virtual address to a physical address by substituting the higher bits in the address, rather than doing complex arithmetic. Example: Assume that we have a TLB mapping of virtual address 0x2CFC7000 to physical address 0x12345000.