Abstract
Memory management plays a key role for any multiprogramming operating system. Memory should be managed such that many processes can be in the memory at the same time .As the physical memory is limited , operating systems make use of virtual memory to run processes which are larger than the physical memory. Virtual memory is a technique using which processes can run even when they are not entirely in memory. Main memory is treated as an array of pages thus separating in to logical memory and physical memory, thus the size of the physical memory is not a limitation for the user.
Memory management in Windows
The physical memory in Windows is divided into a number of physical pages .If the pages are divided in to say 4KB size causes external fragmentation of memory. If the pages are divided into 2MB pages this causes internal fragmentation. Windows uses large pages to better the performance of translation look aside buffer TLB( is a cache used by memory management hardware to improve virtual address translation speed).The physical pages are in one of the following states free page, zeroed page, modified page, standby page ,bad page, transition page, valid page. Valid pages are in processes page tables ,while pages in other states are separated in to list based on their state.
Virtual memory in Windows is implemented by demand paging with clustering. Demand paging is method in which the pages are loaded in to the memory as they are required in the course of the process’s execution. Clustering is used by Windows in this when there is a page fault (page is required for the further execution of the process) along with the page ,many other pages are also moved in to the physical memory. The free pages are handled by the virtual memory manager.
Every process has a working set minimum(it is the minimum number of pages the process will definitely have in the