Key Takeaways
- Internal fragmentation results in unused space within allocated memory blocks, leading to inefficient utilization.
- External fragmentation causes scattered free memory areas, making it hard to allocate large contiguous spaces.
- Internal fragmentation is more related to fixed partitioning schemes, whereas external fragmentation occurs in dynamic memory allocation.
- Compaction techniques help reduce external fragmentation but are costly in performance and processing power.
- Choosing between internal and external fragmentation issues depends on system design and workload characteristics.
What is Internal Fragmentation?
Internal Fragmentation occurs when allocated memory blocks contain unused space because the requested size is smaller than the assigned block. Although incomplete. This leads to a wastage of memory within each partition or block.
Memory Wastage in Fixed Partitions
In fixed partition schemes, each partition size is predetermined, which can leave leftover space unused if the process size is smaller. This unused space within the partition is the core of internal fragmentation.
Impact on System Efficiency
Internal fragmentation reduces overall memory efficiency cause, even when memory is available, it cannot be used for other processes. This causes decreased system performance and higher costs.
Examples of Internal Fragmentation
For instance, when a process requires 30 KB but is allocated a 64 KB block, the remaining 34 KB goes wasted. This inefficiency accumulates over time in multi-process systems.
Mitigation Techniques
Using variable-sized partitions or dynamic memory allocation helps reduce internal fragmentation. However, these methods can introduce complexity in memory management,
What is External Fragmentation?
External Fragmentation occurs when free memory is divided into small, non-contiguous blocks, making it impossible to allocate larger chunks despite having enough total free space. The fragmentation spreads across the system, causing allocation failures.
Fragmentation in Dynamic Allocation
In systems that allocate memory dynamically, as processes are loaded and removed, gaps form between allocated blocks. These gaps is the primary cause of external fragmentation,
Effects on Memory Utilization
External fragmentation reduces the effective usable memory, leading to inefficient use of resources even when enough total free space exists. This results in process termination or slowdowns.
Real-World Examples of External Fragmentation
For example, a system might have 200 MB of free memory in total, but because it is scattered into small pieces, a process needing 150 MB cannot be allocated. The scattered free space are useless for large processes.
Strategies to Reduce External Fragmentation
Memory compaction, which relocates processes to create larger contiguous free blocks, and paging techniques, which avoid external fragmentation altogether, are common solutions.
Comparison Table
Below is a detailed comparison highlighting different aspects of internal and external fragmentation:
| Aspect | Internal Fragmentation | External Fragmentation |
|---|---|---|
| Cause | Fixed-sized memory blocks | Dynamic memory allocation with variable sizes |
| Memory Waste | Unused space within allocated blocks | Unused spaces scattered outside allocated blocks |
| Impact on Allocation | Prevents use of leftover space inside blocks | Prevents large blocks from being allocated despite sufficient total free space |
| Common in | Partitioned fixed memory systems | Dynamic partitioning and heap memory systems |
| Management Complexity | Relatively simple, fixed size | Requires compaction or paging to manage |
| Solutions | Variable-sized partitions, better fit algorithms | Memory compaction, paging, segmentation |
| Performance Impact | Minor in small fixed systems | High during compaction processes |
| Effect on System Efficiency | Can lead to significant waste if not managed | Reduces usable memory despite adequate total free space |
| Memory Allocation Speed | Fast, no need for complex management | Slower, due to need for defragmentation or paging |
| Real-World Analogy | Filling a small box with a larger, empty space inside | Filling a room with many small, disconnected pieces of furniture |
Key Differences
- Cause of wastage in internal fragmentation is due to fixed block sizes, whereas external fragmentation’s wastage stems from scattered free spaces.
- Memory management complexity is lower for internal fragmentation because it involves fixed size allocations, while external fragmentation requires advanced techniques like defragmentation or paging.
- Impact on large process allocation is more evident in external fragmentation, where fragmented free space prevents large blocks from being allocated, despite enough total free memory.
- Efficiency loss in internal fragmentation is caused by unused space within allocated blocks, while in external fragmentation, the loss is due to inability to utilize free memory due to scattering.
FAQs
Can external fragmentation be completely eliminated in a system?
No, in systems with dynamic memory allocation, some degree of external fragmentation is inevitable. However, techniques like paging and segmentation can minimize it significantly.
Does internal fragmentation occur more in systems with variable or fixed partition sizes?
Internal fragmentation is more prevalent in fixed partition systems because fixed sizes do not match process needs, leading to wasted space inside partitions.
What are the main trade-offs of using memory compaction to reduce external fragmentation?
Memory compaction can improve utilization but at the cost of increased processing time and system overhead, which might slow down performance during the process.
Which fragmentation type affects overall system performance more?
External fragmentation has a greater impact because it can prevent large process allocations despite available total memory, causing delays and resource underutilization.