Fragmentation in OS

• Fragmentation in OS Operating System represents the amount of memory waste during allocation  using different Memory Management technique.
• Fragmentation plays an important role in memory allocation.
• Methods which produce less fragmentation is considered good for memory allocation.
• Some time it seems confusing for students to understand the exact difference between internal and external fragmentation.

Before understanding the difference between internal and external fragmentation we need to understand the meaning of fragmentation in the context of memory.

So let’s see what is fragmentation in os.

• Fragmentation in OS  refers to the unused memory that the memory management system cannot allocate.
• Fragmentation in Operating System is of two types one is  External fragmentation and second is Internal Fragmentation.

Difference between External and Internal Fragmentation

• External Fragmentation is waste of memory between partitions caused by scattered non-contiguous free space.
• External Fragmentation occurs when total available memory space is enough to satisfy the request for a process to be allocated, but it is not continuous.
• Selection of first fit and best fit can affect the amount of fragmentation.
• It is severe in variable size partitioning schemes. Compaction is a technique that is used to overcome this.

• Internal fragmentation the is waste of memory within a partition caused by difference between size of partition and the process allocated.
• Internal Fragmentation refers to the amount of memory, which is not being used and is allocated along with a process request i.e. available memory internal to partition. It is severe in fixed partitioning schemes.
• Internal fragmentation can be decreased by choosing smallest partition which can hold a process.