External debris may be generated and variable partitions may be segmented internal fragmentation parameters are paged segment fixed partitions paged
In the virtual storage solutions commonly used strategy has two paged demand paging and pre-paging
Mobile technology can solve external fragmentation can not solve internal fragmentation
Page replacement strategy FIFO page replacement algorithm (FIFO) is always the first choice swapped PageOut not recently used page replacement algorithm (LFU) is the total number of pages of this method is called to be accessed by selecting options the minimum number of pages to call up the desired page replacement algorithm (OPT) is no longer required or selected after the longest time after the total number of pages will be used to bring up the least recently used page replacement algorithm (LRU) always choose the longest time to visit had PageOut
Page storage management program in the logical memory addresses into two address page number and a byte of eight three-byte portion 24 so that the address length is 24 because the page address representing page number occupies 10 therefore 2 ^ 14 14 = 16384 That process has up to 16,384 pages
In a paged memory management scheme Page Size 2kb = 2 ^ 11 process address space of 2 ^ 29 = 512MB page number accounted for 29-11 = 182 ^ 18
Fixed allocation in some areas replacement allocation scheme is based on the type of process is allocated a fixed number of pages of memory space for each process during the entire run are no longer changed when using this strategy if the process occurs in the missing pages can only run from the N pages to swap out a process of selection and then enter a memory space allocated to ensure that the process remains unchanged
Variable partition process runs in its memory pages can be allocated dynamically increase or decrease a certain number of pages of memory for each process
All replacement process is running when it is not enough pages can be replaced from the heat in the system at any process
Virtual address length is 20 bits of the address 0 through address 10 is the size of each page is 4KB page number is 12 ~ 20 are allowed in the address space of 2 ^ 8 allows a maximum process has 8 * 2 ^ 2 ^ 12 = 2 ^ 20 bytes
When a process interrupt occurs page and select a page to which parameters and flags out of the page corresponding page table entry need not be changed: No access memory block modified bit bit bit protection
Organized memory allocation table: Bit charts illustrating idle page table, the table fast idle
Scheduled to run new processes: memory-resident bit block numbers need to change the access bit
When moving a program in memory is necessary to read all of the code and data memory for memory relocation code and the read data is written to the memory to modify the target region allocated memory free list table modification
The need to increase in the page table when using the virtual page storage management page number of significant bits of the page frame number to access bit modified bit protection bit disables the caching of which the contents of a page a process is modified, accessed bit and modified bit in the page table for you must be modified
Virtual page storage management requires the following hardware support: 1. a large enough system capacity external memory 2. The system has a certain amount of memory 3. The hardware provides virtual address mapping mechanism 4. The page fault handling mechanism
Disk in a paged memory need to modify the memory block number resides bit Access Bit