Question

What is external and internal fragmentation?

Answer 1

Internal fragmentation occurs when the memory allocator leaves extra space empty inside of a block of memory that has been allocated for a client. This usually happens because the processor’s design stipulates that memory must be cut into blocks of certain sizes -- for example, blocks may be required to be evenly be divided by four, eight or 16 bytes. When this occurs, a client that needs 57 bytes of memory, for example, may be allocated a block that contains 60 bytes, or even 64. The extra bytes that the client doesn’t need go to waste, and over time these tiny chunks of unused memory can build up and create large quantities of memory that can’t be put to use by the allocator. Because all of these useless bytes are inside larger memory blocks, the fragmentation is considered internal.

What Is Internal & External Memory Fragmentation?

by Erica Kasper



Memory fragmentation occurs when a system contains memory that is technically free but that the computer can’t utilize. The memory allocator, which assigns needed memory to various tasks, divides and allocates memory blocks as they are required by programs; when data is deleted, more memory blocks are freed up in the system and added back to the pool of available memory. When the allocator’s actions or the restoration of previously occupied memory segments leads to blocks or even bytes of memory that are too small or too isolated to be used by the memory pool, fragmentation has occurred. Fragmentation can take a significant bite out of a computer's free memory and it is often the cause of frustrating out-of-memory error messages.

Internal Fragmentation



Internal fragmentation occurs when the memory allocator leaves extra space empty inside of a block of memory that has been allocated for a client. This usually happens because the processor’s design stipulates that memory must be cut into blocks of certain sizes -- for example, blocks may be required to be evenly be divided by four, eight or 16 bytes. When this occurs, a client that needs 57 bytes of memory, for example, may be allocated a block that contains 60 bytes, or even 64. The extra bytes that the client doesn’t need go to waste, and over time these tiny chunks of unused memory can build up and create large quantities of memory that can’t be put to use by the allocator. Because all of these useless bytes are inside larger memory blocks, the fragmentation is considered internal.


External fragmentation happens when the memory allocator leaves sections of unused memory blocks between portions of allocated memory. For example, if several memory blocks are allocated in a continuous line but one of the middle blocks in the line is freed (perhaps because the process that was using that block of memory stopped running), the free block is fragmented. The block is still available for use by the allocator later if there’s a need for memory that fits in that block, but the block is now unusable for larger memory needs. It cannot be lumped back in with the total free memory available to the system, as total memory must be contiguous for it to be useable for larger tasks. In this way, entire sections of free memory can end up isolated from the whole that are often too small for significant use, which creates an overall reduction of free memory that over time can lead to a lack of available memory for key tasks.

Answer 2

HEY FRIEND HERE IS UR ANSWER,

The key difference between internal fragmentation and external fragmentation is that in internal fragmentation fixed sized memory blocks are assigned to process whereas in external fragmentation variable sized memory blocks are assigned to process.

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