Computer Science - Operating Systems Concepts - Discussion

Fragmentation is a phenomenon in which storage space is used inefficiently, reducing capacity and often performance. Fragmentation leads to storage space being "wasted", and the term also refers to the wasted space itself.

Compaction means defragmentation.

If it means compaction so how it is "temporarily removed"?

So what is compaction?

And how is fragmentation and compaction co-related?

Defragmentation means storing the complete file in a smallest number of contiguous regions. That is, it tries to stores a file as one complete unit if that size of contiguous memory is available. Suppose process A has fragments A1, A2, A3, process B has fragments B1, B2.

Now, suppose memory layout is |A1|B1|A2|A3|B2|, after defragmentation we have |A1|A2|A3|B1|B2|.

Defragmentation can also contribute to compaction.

Compaction means moving the "in-use" memory areas to eliminate holes caused by terminated processes.Suppose we have five processes A, B, C, D, E, allocated as |A|B|C|D|E| in memory. After sometimes, the process B and D are terminated.

Now we have memory layout as |A| |C| |E|. After applying compaction we will have |A|C|E| | | i.e instead of two one-block memory unit we have one two-block memory unit.

Thnak you @Amit.