Memory Management

Memory Management Requir

POS/355

8/5/2013

Memory Management Requirements

Memory management is crucial when building a multiprogramming system because, as stated in Operating Systems 7e, “memory needs to be allocated to ensure a reasonable supply of ready processes to consume available processor time.” (Stallings, 2012) Memory management is meant to meet five main requirements, these requirement are relocation, protection, sharing, logical organization and physical organization.

Because the main memory in a multiprogramming system is shared with many processes, relocation becomes essential. Programs cannot know what other programs will be running in main memory before they are executed, therefor the programs must be addressed in a way that allows the processor and operating system to locate the program wherever it may currently reside in main memory. This becomes important when programs are swapped from main memory to disk or vice versa, because of the limitations it would cause if the program needed to be placed in the same region of memory each time it was swapped. Instead with relocation the process is able to be relocated to a different area of memory. (Stallings, 2012)

The protection requirement is meant to stop any unwanted interference from other processes. (Stallings, 2012) This requirement is actually made more difficult by the relocation requirement because the location of programs in main memory can change so regularly. Because of this, a quick check must be made by the processor each time a process references the main memory. This is explained well in the book Operating Systems 7ed, “all memory references generated by a process must be checked at run time to ensure that they refer only to the memory space allocated to that process.”

The protection requirement must still be flexible enough to allow for the sharing of portions of the main memory with several different processes (Stallings, 2012). This process is summarized well in the...