Which algorithm in a computer Operating System uses paging for memory management? 

The correct answer is Page Replacement.

Key Points

• In a computer operating system that uses paging for virtual memory management, page replacement algorithms decide which memory pages to page out, sometimes called swap out, or write to disk, when a page of memory needs to be allocated. 
• Page replacement happens when a requested page is not in memory (page fault) and a free page cannot be used to satisfy the allocation, either because there are none, or because the number of free pages is lower than some threshold.
• When the page that was selected for replacement and paged out is referenced again it has to be paged in (read in from disk), and this involves waiting for I/O completion. 
• This determines the quality of the page replacement algorithm: the less time waiting for page-ins, the better the algorithm.
• Replacement algorithms can be local or global.
• When a process incurs a page fault, a local page replacement algorithm selects for replacement some page that belongs to that same process (or a group of processes sharing a memory partition). 
• A global replacement algorithm is free to select any page in memory.
• Local page replacement assumes some form of memory partitioning that determines how many pages are to be assigned to a given process or a group of processes. 
• Most popular forms of partitioning are fixed partitioning and balanced set algorithms based on the working set model. The advantage of local page replacement is its scalability: each process can handle its page faults independently, leading to more consistent performance for that process. However global page replacement is more efficient on an overall system basis.