Page size is 4KB, the total of 2 * 1024 * 1024/4 page table entry for each page is represented by a 4-byte physical page number, you need 2 * 1024 * 1024/4 * size of the page table 4, each page table 4kb i.e. 2 * 1024 * 1024/4 * 4 / * 4 = 512 pages 1024
The number of physical pages Belady phenomena allocated to the process but also increase the number actually increased. FIFO FIFO algorithm will be the vision
Within each loop through the 100 integer variable, the equivalent of two pages will lead to the middle of the two missing pages, a total of 50 times the outer loop, 50 * 2 = 100 page fault
Hardware address mapping process is usually done, address mapping is to convert the virtual address into a physical address, some of the contents of the page table entry if the hardware is fixed according to the valid pages to determine access page table entries already in memory
The use of cache memory to store the current year a small number of the most frequently accessed page number of the active page, the cache is called fast table, also called transition detection buffer (TLB) in the table fast table is part of the process page table switched fast time table needs to be updated because of the different process's page table without a pair of quick query tables and page tables are parallel fast once found in the table have to check with the page number of the same logical page number stops to find memory page tables directly using fast logical page number in the table
Refers to dynamic relocation procedure is loaded, no address translation, but directly loaded into the program memory, the program during execution, whenever one instruction by star hardware address translation mechanism instruction logical address converted into an absolute address
Best fit algorithm: find out from all of the space to meet the requirements of the job, and the size of the smallest space partition, this method allows debris as small as possible.
Size of the virtual memory space by limiting computer AddrBits
The least recently used LRU algorithm in the virtual page storage management system, the first time since the most recent replacement page is not accessible
In the virtual page management system, each page table entry must contain are: 1-bit write valid bit 2. 3. 4. Modification flag bit access
Debris exists outside the operating system are various storage methods: Dynamic partitions and storage management segment
Memory tightening the fragmented free areas to focus on a large empty area
Page dispensing advantage: 1. Because he did not want the job and the process of continuous data blocks and stored in memory, so as to effectively solve the fragmentation problem 2, page dynamic storage management provides unified management of virtual memory and external memory storage implementations so users can take advantage of storage space greatly increases both improve the efficiency of the organization and it helps multi-channel program
0.4ps fast memory access time table hit rate 90% 10% 0.4 * 0.04 = 0.04 + 0.4 hit the page table for the effective access time = 0.44
External memory (disk) demand paging file area is divided into two sections for storage of files, used to store the swapped page is not running all the pages should be transferred from the file area of the exchange zone can be rapid collection and use of virtual storage memory management scheme must have the following characteristics: a dynamic memory addresses, memory processes movable die. 2. Not all procedures required to load as memory, processes can run so there are page-leaf stage stage
In the virtual storage system so that operation of the process section after class loading, virtual storage technology allows the user to use more storage space in physical memory, the hardware must be implemented virtual memory support
A secondary index to access a secondary index to access the instruction three visits
In order to improve memory utilization and reduce fragmentation within the page is divided into the number associated with the page table, you can find a balance
Jitter that occurs when the prevention of the use of working set memory paging algorithm
The method commonly used to manage the physical memory space are: spatial block list method, bit map method, the idle page table
Statements about the virtual page storage management scheme: 1 and the like into the memory size of a power of 2 memory blocks called pages block 2. The system virtual address space into the page size of the page frame 3 same virtual page on the physical space is not required to implement the logic address stored in a row 4. the hardware mechanism to a physical address conversion
Obtained before each processor memory operation, you must first be loaded into memory portion
CPU utilization of 50% hard disk busy rate of 30% means that the CPU usage can also increase the number of processes
3% CPU utilization rate of 97% disk busy too high disk utilization affect the proper execution efficiency of the CPU to reduce the number of processes to improve system efficiency
Local procedures divided into two parts temporal locality and spatial locality Spatial locality refers to the presence of a number of cycles of the time sequence of program code means locality procedure
Can support multi-channel programming of storage management solutions are: variable partition management page storage management storage management segment fixed paged memory management
From simple page storage management solutions to the virtual page storage management program, the page table entry typically require additional information are: significant bits modified to access the site
Least Recently Used algorithm LRU algorithm time slice CLOCK not recently used algorithm bits required to access the NRU
Also known as resident significant bit position indicates the presence bit or interrupt the page in memory or external memory
Access bit and modified bit is called when the page replacement
Information primarily to enable the page table is loaded with the difference between external memory and export memory page table page table of information easy
Page size page storage management can be of different sizes in order to improve memory utilization as needed using a variety of different sized pages a user process can change the page size to set the page size only by the operating system during operation
The introduction of the virtual page storage management system, which will appear in the following phenomena: 1 Page jitter 2.Belady page fault phenomenon 3. 4. wrong page
Relocation is the memory logical address space into real memory address space Wu relocation process divided into two: 1. 2. Static Dynamic relocation relocation
Sequence said page storage management program address translation is done by the operating system
Fixed partitions and variable storage management program uses a continuous allocation strategy and these two methods are the units all at once allocated memory space as the entire process
Every page Become page address starts from 0 addressing, the page number is within the upper part of the page address in the address portion of the address is the status of
Not recently used page replacement algorithm (LFU) may be used in accordance with the number of times within a period of time how many pages can be retrieved pages
Ideal page replacement algorithm (OPT) will no longer require the replacement or re-longest in the future will use the page
Daemon is to start running in the background by the general system automatically activates a script to start or manage a super user at boot
Address conversion page management process is isolated by the page table corresponding to the address obtained by adding the actual physical address to be accessed during a memory page table page table space area, and bitmap data structure
Described virtual memory management scheme working set size and working windows operating system is closely related to physical pages should provide the working set size for each process
Mobile technology can concentrate dispersion free zone, improve memory efficiency, ease of operation dynamic memory expansion using mobile technology to pay attention to the following questions: 1. Mobile technology will increase the system overhead is moved by 2. Move should be reduced as much as possible when conditions require the use of mobile technology the number of jobs and process information can be moved from the lower area to address in the memory address area high can also be moved from low to high address area address area
Bumpy phenomenon is due to lack of work caused by the high rate of pages and other changes over time using the working set can solve the problem bumps