Operating Systems Date:26/3/14 By B Harishma 11CS30009. Paging. Logical Address Address generated by the CPU Divide logical memory into blocks of same size called PAGES . Physical Address Address seen by the memory unit Physical address of a process can be non contiguous.
Divide logical memory into blocks of same size called PAGES.
Physical address of a process can be non contiguous.
Divide physical memory into fixed size blocks called FRAMES.
“Page table is used to translate logical address to physical address”
Task is to perform mapping.
Address Translation scheme:
Page number Page offset
p is an index into the page table contains base address of each page in physical memory.
d is the displacement within the page and when combined with the physical memory address that is sent to the memory unit.
External Fragmentation: Holes are scattered in memory.
Paging scheme does not suffer from external fragmentation.
Reason : There is no need of contiguous memory.
But, it does suffer from --------------------INTERNAL FRAGMENTATION
Reason : Pages and frames are basic units and cannot be divided further.
Small page size low page sizesize of page table increases I/O operations from disk increases initially slow
User’s View: Process Contained in single contiguous memory space.
By implementation, process can only access its memory--- PROTECTION.