Key Takeaways
- Internal fragmentation happens when allocated space has leftover unused bits that can’t be used again, wasting memory within a block.
- External fragmentation occurs when free memory is split into small pieces scattered across the storage, making it hard to find large contiguous spaces.
- Contiguous memory allocation methods are more prone to external fragmentation, while fixed-sized allocations tend to increase internal fragmentation.
- Memory compaction can help reduce external fragmentation but can be costly and complex to implement.
- Choosing between internal and external fragmentation depends on workload patterns and system design considerations.
What is Internal Fragmentation?
Internal fragmentation occurs when allocated memory blocks are slightly larger than the data stored, leading to unused space inside the block. This unused space, although allocated, can’t be used for other data, resulting in wastage.
Memory Block Size Mismatch
When memory is divided into fixed sizes, any data smaller than the block leaves leftover space. This mismatch causes internal fragmentation, especially with smaller data sizes.
Allocation Strategies
Some allocation methods allocate fixed-size blocks to simplify management but increase internal fragmentation. Dynamic strategies try to minimize waste but may still leave internal gaps.
Impact on System Performance
Excess internal fragmentation reduces effective memory available for processes, potentially causing more frequent allocations or swapping. Although incomplete. It also leads to inefficient memory usage overall.
Examples in Real-World Systems
File systems allocate fixed sectors, which can leave small unused spaces inside each sector. This wastage is a classic example of internal fragmentation in storage.
What is External Fragmentation?
External fragmentation refers to the scattered free spaces across memory, preventing the allocation of large contiguous blocks despite enough total free memory. It makes large data allocations difficult or impossible.
Memory Allocation Fragmentation
When processes are assigned and released memory dynamically, free spaces become fragmented into small chunks. Although incomplete. Over time, this leads to difficulties in finding suitable blocks for new processes.
Effects on System Efficiency
External fragmentation can cause increased overhead for memory management as algorithms attempt to find contiguous spaces, slowing down performance. Although incomplete. It may also lead to memory wastage.
Memory Compaction Techniques
Memory compaction involves shifting processes to merge small free areas into larger ones. Although it reduces external fragmentation, it can be time-consuming and disrupt system operations.
Real-World Examples
In operating systems, when programs allocate and free memory frequently, small gaps appear, making it hard to allocate large data structures despite enough total free space.
Comparison Table
Below table compares internal and external fragmentation across different aspects, providing clear distinctions.
| Aspect | Internal Fragmentation | External Fragmentation |
|---|---|---|
| Definition | Unused space within allocated memory blocks due to size mismatch. | Free memory scattered in small chunks preventing large allocations. |
| Typical Cause | Fixed-size memory allocations exceeding data size. | |
| Memory Waste | Waste occurs inside blocks, unusable leftovers. | |
| Impact on Storage | Leads to inefficient use of allocated space. | |
| Management Solution | Using variable-sized blocks or better packing algorithms. | |
| Impact on Allocation | Less flexible, may cause underutilized memory. | |
| Impact on Free Space | Does not affect free space distribution directly. | |
| Allocation Difficulty | Less problematic; space is available but wasted. | |
| Example System | Fixed sector storage in hard drives. | |
| Best Mitigation | Reducing block sizes or dynamic allocation strategies. | |
| Main Drawback | Memory is wasted within blocks, reducing efficiency. |
Key Differences
- Internal Fragmentation is clearly visible in allocated blocks that have leftover unused space.
- External Fragmentation revolves around the scattered free memory that cannot be combined easily.
- Internal fragmentation is less problematic when data sizes match block sizes, whereas external fragmentation worsens when many small free areas exist.
- External fragmentation relates to the difficulty of allocating large memory chunks despite overall sufficient free space.
FAQs
What are the typical methods to prevent external fragmentation?
Memory compaction and using variable-sized memory blocks are common approaches to reduce external fragmentation, but they require system overhead and careful management to avoid performance hits.
How does internal fragmentation affect file storage devices?
Storage devices with fixed sector sizes leave small gaps within sectors when files are smaller than the sector size, leading to wasted space and decreased storage efficiency.
Can external fragmentation be completely eliminated?
Complete elimination is difficult, but techniques like defragmentation and memory compaction significantly reduce external fragmentation, improving system performance.
What is the relation between fragmentation and system speed?
High fragmentation levels cause increased processing time to find suitable memory blocks, slowing down overall system response and increasing latency.