Need for Paging

Disadvantage of Dynamic Partitioning

The main disadvantage of Dynamic Partitioning is External fragmentation. Although, this can be removed by Compaction but as we have discussed earlier, the compaction makes the system inefficient.

We need to find out a mechanism which can load the processes in the partitions in a more optimal way. Let us discuss a dynamic and flexible mechanism called paging.

Need for Paging

Lets consider a process P1 of size 2 MB and the main memory which is divided into three partitions. Out of the three partitions, two partitions are holes of size 1 MB each.

P1 needs 2 MB space in the main memory to be loaded. We have two holes of 1 MB each but they are not contiguous.

Although, there is 2 MB space available in the main memory in the form of those holes but that remains useless until it become contiguous. This is a serious problem to address.

We need to have some kind of mechanism which can store one process at different locations of the memory.

The Idea behind paging is to divide the process in pages so that, we can store them in the memory at different holes. We will discuss paging with the examples in the next sections.