Memory Management
1。Storage management outlined
Storage management : users of the main memory for the region, the management of the fixed area, Variable Area, page style, struts, and virtual memory management of the page.
Memory is divided into two categories : main memory (memory) and the auxiliary memory (secondary stock).
Storage management to discuss the memory management system and user memory is the process of regional operations. However, the region's share of the general operating system is a permanent, and therefore the management of main memory against memory regional users.
Storage allocation mechanism can be effective in the process user requests for immediate distribution of the storage space. and the timely recovery of the user no longer needs to use other processes.
2。Cover and Technology
Early in the coverage of technology is the operating system for memory expansion, coverage of the use of space technology can process addresses most of the code and data stored in secondary deposit. Just in memory to retain the current need for the implementation of the code, which calls for the exchange of information between memory and auxiliary survival.
3。Pagination
Pagination : The basic idea of the memory space divided by a fixed block size of these pieces as physical block. Then, on the basis of equal size and customer operations such as address space is divided into a series of pages long. After months of work by a number of pages, each page can be scattered in different physical storage bins. To determine a physical piece of work with which all pages correspond to each operation to introduce a data structure called the page table.
4。Segmentation
Segmentation is the idea : a description of the structure of two-dimensional address space. In accordance with the procedures of the logical structure will be divided into several independent of each occupy a row of the storage area. But not all of the row between. To manage storage space operations, the use of the operating record of the table in memory of the start address and length.
5。Virtual Storage Technology
Virtual memory and storage technology is secondary to keep unity. supplemented with limited memory and the larger the deposit is a relatively large operation logical address space technology This system users in the preparation process ceased to be effective memory capacity constraints.
Method : In the operation together with the procedures, as long as the procedures necessary part of the load memory, and the rest still exist on the presence in the secondary. When the process of implementing procedures need not visit the memory data or code, transferred from its operating system.
Virtual Memory should provide hardware support :
The Commission has a capacity large enough deposit can accommodate all the address space operations.
A certain physical capacity of the memory space.
Achieve the virtual address-mapping hardware real change of address.
6。Page Replacement Algorithms
Pages to the process : a process in which the operation of the sequence as its page to page.
Page failure rate : there will not need to visit the page or pages of the phenomenon known as the Page Fault failure.
Page Replacement Algorithms
Best replacement algorithm : From 1988 to eliminate those pages will never use.
Algorithm : The Application of the earliest memory pages can no longer be transferred to the possibility of a visit by memory pages larger than the new entrants.
Algorithm : In the past, most recently with a long time within a certain period of time has not yet visited pages in the near future will not be visiting.
Approximate LRU algorithm : setting up a page for each trip.
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