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Table of Contents
Key Takeaways
- Internal fragmentation occurs when allocated memory blocks contain unused space, leading to inefficient memory use.
- External fragmentation is caused by scattered free memory spaces, making it hard to find contiguous blocks needed for large processes.
- Internal fragmentation is more predictable, as it results from fixed block sizes, while external fragmentation is more complex due to variable free spaces.
- Memory compaction can reduce external fragmentation but requires additional processing time and resources.
- Choosing between techniques to minimize either fragmentation depends on system requirements and workload patterns.
What is Internal Fragmentation?
Internal fragmentation happen when memory allocated to a process has unused space within the assigned block. This waste occurs because of fixed-size memory blocks that don’t perfectly fit process needs.
Memory Block Size Mismatch
When fixed sizes are used for memory allocation, smaller processes may leave leftover space inside their blocks. This unused part of allocated memory can’t be used by other processes, leading to inefficiency.
Waste Within Allocated Spaces
Internal fragmentation causes a portion of memory to be wasted because processes don’t utilize the entire allocated block. Over time, this build-up can reduce overall system performance.
Impact on System Performance
As internal fragmentation increases, more memory are tied up, which can limit the number of processes the system can handle efficiently. This results in slower response times and potential bottlenecks.
Examples of Fixed Block Allocation
Commonly seen in systems using fixed partitioning or slab allocation, where each process gets a pre-defined size. When process sizes don’t match, internal gaps appear.
What is External Fragmentation?
External fragmentation refers to free memory being broken into small, non-contiguous blocks scattered across the system. This makes it difficult to allocate large contiguous memory spaces to processes,
Dispersed Free Spaces
As processes are allocated and deallocated, free memory becomes scattered, creating tiny gaps. These gaps is too small to be useful for new large processes,
Difficulty in Allocating Large Blocks
The scattered nature of free memory prevents the system from fulfilling requests that require large contiguous spaces. This leads to process waiting or failure to allocate memory.
Effects of Memory Allocation and Deallocation
Repeatedly allocating and freeing memory causes external fragmentation. Over time, the free memory gets divided into small pieces, even if total free memory is sufficient.
Memory Compaction Techniques
To combat external fragmentation, systems sometimes move allocated blocks to consolidate free space. Although effective, this process are resource-intensive and can cause delays.
Comparison Table
Below is a comparison of internal and external fragmentation across various real-world aspects:
| Aspect | Internal Fragmentation | External Fragmentation |
|---|---|---|
| Causing factor | Fixed size memory blocks | Dynamic memory allocation and deallocation |
| Memory waste | Unused space inside allocated blocks | Small scattered gaps between free blocks |
| Predictability | More predictable due to fixed sizes | Less predictable, depends on process behavior |
| Impact on performance | Reduces available usable memory | Prevents large memory allocation, causes delays |
| Management method | Choosing appropriate block sizes | Memory compaction or paging |
| Effect on system utilization | Lower efficiency due to wasted space | Reduced due to inability to allocate large blocks |
| Typical systems affected | Fixed partitioning systems | Dynamic partitioning systems with frequent allocation/deallocation |
| Solution approaches | Use smaller or variable-sized blocks | Memory defragmentation or paging techniques |
| Example scenario | Allocating 64KB blocks to small processes leaves 16KB unused | Freed spaces scattered after process exits, unable to allocate 200KB process |
| Complexity of management | Relatively simple, fixed sizes | More complex, involves moving memory blocks |
Key Differences
- Internal fragmentation is clearly visible in the wasted space within fixed-sized memory blocks, while external fragmentation is noticeable when free memory is broken into tiny, unusable pieces scattered across the system.
- Internal fragmentation revolves around the inefficiency caused by the mismatch between allocated block size and process needs, whereas external fragmentation relates to the scattered free spaces preventing large memory requests.
- Internal fragmentation is more predictable cause it depends on fixed block sizes, while external fragmentation is more unpredictable, based on the pattern of memory allocations and deallocations.
- External fragmentation relates to the difficulty in finding contiguous memory chunks, and can be mitigated by memory defragmentation, but internal fragmentation requires choosing better block sizes or more advanced memory management techniques.
FAQs
Can external fragmentation be completely eliminated?
Complete elimination of external fragmentation is difficult because memory constantly changes with process allocations and deallocations. Techniques like memory compaction can reduce it, but not eradicate it entirely.
Does internal fragmentation affect system security?
While not directly related to security, internal fragmentation can cause inefficient memory use that might lead to unpredictable system behavior or vulnerabilities if memory are exhausted unexpectedly.
How does paging help with external fragmentation?
Paging divides memory into fixed-size pages, which removes the need for contiguous free space, thus eliminating external fragmentation. Although incomplete. It allows processes to use non-contiguous physical memory efficiently.
What is the main trade-off when reducing internal fragmentation?
Reducing internal fragmentation involves smaller block sizes, which can increase management overhead and complexity, potentially leading to more fragmentation or higher processing costs.
