《操作系统教学资料》2013-CHAP5.pdfVIP

Chapter5 Memory Management (存储器管理) 5.1 Requirements of MM (存储器管理需求) 5.2 Fixed Partitioning (固定分区) 5.3 Dynamic Partitioning (动态分区) 5.4 Simple Paging (简单分页) 5.5 Simple Segmentation(简单分段) 5.6 Virtual Memory (虚拟存储器) 5.7 Policies for Virtual Memory (虚拟存储器管理策略) 5.8 Terminology(术语) Memory Management (存储器管理) 5.1 Requirements of MM(存储器管理需求) In a multiprogramming system many user programs will share the memory and it is vital that this sharing be done in the most effective and efficient manner. Requirements: The following requirements will characterize the objectives of a memory management subsystem: •Relocation •Protection •Sharing •Logical organization •Physical organization We consider each of these in turn: Memory Management (存储器管理) 5.1 Requirements of MM(存储器管理需求) Relocation To increase CPU utilization, the OS might have to suspend a process out to disk.  When the program is loaded back into memory it is not likely to be placed in the same location •It will be relocated It may also be necessary to relocate processes in memory so as to free up larger contiguous areas of memory in order to bring in more programs. Memory Management (存储器管理) 5.1 Requirements of MM(存储器管理需求)  Protection The OS and all user processes must be protected from the accidental or malicious interference of another process. The memory references made by a process must be checked at run time to ensure that they are being made to areas of memory that are “legal” for that process. •This cannot be guaranteed by the compiler or OS alone.