Question

Compare Windows and Linux memory systems used by the OSes.

Answer 1

Hello, the answer of the question is written below into tabular form.

We will compare Windows and Linux memory systems with varieties of features mentioned in below table:

Features	Windows	Linux
Data Structures	It uses tree data structure. Each node of the tree is called Virtual Address Descriptors (VAD). VAD marks each node as free, committed or reserved. Committed nodes are those nodes that are currently being used. Free nodes are unused nodes.	It uses linked list data structure. It maintains a list of vm_area_structs. This list is searched whenever a page is to be found. It also records the range of address, protection mode and the direction in which it grows (up or down). If number of entries becomes more than 32, Linux converts linked list into a tree.
Distribution of Process Address Space	Windows on 32 bit x86 systems can access up to 4GB of physical memory. Windows allows each process to have its own 4GB logical address space by using paging. The upper 2GB is kept for windows kernel mode. The lower 2GB of the address space is reserved for user mode.	3GB of memory space is reserved for user mode 1GB is kept for Kernel mode.
Paging	Windows uses cluster demand paging Pages are brought in the memory when they are needed. Instead of bringing pages one by one, eight pages are brought in the memory simultaneously. It makes use of working set model. Working set is the amount of memory currently assigned to the process. It contains the pages that are in the main memory. Size of working set can be changed accordingly. Windows uses Two Level Paging	Linux uses demand paging with no pre paging Linux do not swap the entire process instead uses a lazy swapper. It never swaps a page into the memory unless that page is needed. Instead of swapping in a whole process, the pager swaps only necessary pages into memory. It thus avoids reading pages that will not be used, this decreases swap time and amount of physical memory required.Linux uses three level paging
Address structure	Address is divided into two parts: Page number Page offset	Linear address is broken into four parts: Global Directory. Middle Directory. Page Table Offset.
Page replacement	Windows uses FIFO First in First out Page Replacement Algorithm. The oldest page is chosen for replacement. It suffers from be lady’s anomaly. Page fault rate may increase when we increase number of frame. It has low performance. It has maximum number of page faults.	Linux uses LRU Least Recently Used Page Replacement Algorithm. The page that is not used for a long period of time is selected as victim page and is replaced. Implemented in two ways- Counters and stack. In counters, each page table entry is associated with a time-of-use field. The page with smallest time value is replaced. In stack, the page at the bottom is removed and put on the top of the stack. Least recently used is always at the bottom of the stack.

For any doubt and query please comment.
Thank You !