Memory Management

MemoryMemory Management

Memory management system is important part of each operating system. The main function of this system is to manage the memory system of random access memory and the other storing devices which are available on the system. Main tasks that come under the memory management are allocation and deallocation of memory to the various processes running on the system. The memory management system should be optimized as its function affects the speed and the performance of the operating system.

Windows:

Windows on 32 bit x86 systems accesses upto 4GB of physical memory. This is because that the processor’s address bus which is 32 lines or 32 bits can only access address range from 0x00000000 to 0xFFFFFFFF that is of 4GB. Windows provides 4Gb logical space for each process.. The lower 2GB is for the user mode process and upper 2GB is reserved for Kernel mode code of the Windows. Windows uses the feature of paging for the memory management

Paging allows the software to use a logical memory address than the physical memory address. The paging unit of the processor translates the logical address into the physical address. This allows every process in the system to have its own 4GB logical address space.

Windows provides an independent, 2 GB user address space for each and every application (process) in the system. To the application only 2 GB of memory is appeared to be available than the total memory available. When an application requests more memory than the available memory, Windows NT satisfies the request by paging noncritical pages of memory—from this and/or other processes—to a page file and freeing those physical pages of memory. Thus a global heap exists for no long in the Windows NT. Every process gets the private 32-bit address space from which all of the memory for the process is allocated—including code, resources, data, DLLs (dynamic-link libraries), and dynamic memory. The system is still limited by whatever hardware resources...