NidhiDisclosure: This post contains affiliate links, which means we may earn a commission if you purchase through our links at no extra cost to you.
Key Takeaways
- Internal fragmentation happens when allocated memory blocks have unused space, leading to waste within a single process.
- External fragmentation occurs when free memory is scattered in small chunks, preventing larger allocations despite overall free space.
- Internal fragmentation is affected by fixed-sized memory allocation schemes like partitioning.
- External fragmentation can be reduced through compaction, which rearranges memory to create larger contiguous spaces.
- Managing both types of fragmentation involves different techniques, balancing efficiency and complexity in memory management.
What is Internal Fragmentation?
Internal fragmentation refers to wasted space within allocated memory blocks when the process does not use the entire allocated area. This waste occurs because memory is divided into fixed sizes, which may be larger than the actual data needed.
Fixed-size Allocation
In systems with fixed-sized partitions, each process gets a block of a specific size. If the process needs less, the remaining space inside the block remains unused and wasted.
Memory Wastage
This leftover space inside the allocated memory, though reserved, cannot be used by other processes. It leads to inefficient utilization of available memory resources,
Impact on System Performance
Internal fragmentation causes slowdowns as memory gets filled with small unused spaces, reducing the overall available memory for new processes. Although incomplete. It also increases the need for more memory to meet demand.
Example in Real-world Use
For example, if a process needs 30 KB but the system allocates a 64 KB block, 34 KB of space remains unused. This unused space contributes directly to internal fragmentation.
What is External Fragmentation?
External fragmentation occurs when free memory is divided into small, non-contiguous blocks scattered throughout the system. This fragmentation prevents large memory allocations even if total free memory is sufficient.
Memory Scattering
Over time, as processes allocate and deallocate memory, gaps form between allocated blocks. These gaps are too small for new large processes to use.
Difficulty in Memory Allocation
Allocating large contiguous blocks becomes challenging because free space is fragmented. This can cause processes to wait or fail due to lack of suitable memory segments.
Memory Reorganization Methods
Techniques like memory compaction move allocated blocks to one side, consolidating free space into larger chunks, which reduces external fragmentation.
Real-world Example
Imagine a memory space where small free chunks are scattered, but no single chunk can satisfy a process needing 200 KB, despite total free space exceeding that amount.
Comparison Table
Below is a detailed comparison of internal and external fragmentation highlighting their differences across various aspects.
| Aspect | Internal Fragmentation | External Fragmentation |
|---|---|---|
| Nature of Waste | Unused space within allocated blocks | Unused small gaps between free blocks |
| Causes | Fixed-sized memory partitions or blocks | Repeated allocation and deallocation over time |
| Impact on Memory Utilization | Reduces effective memory available for processes | Prevents allocation of large blocks despite sufficient total free space |
| Management Techniques | Choosing variable-sized partitions, buddy systems | Memory defragmentation, compaction |
| Efficiency | Leads to wastage within each allocated segment | Causes delays in memory allocation, fragmentation delays |
| Occurrence | Common in fixed partition systems | Happens over long-term dynamic memory operations |
| Memory Allocation Style | Pre-allocated fixed blocks | Flexible, dynamic allocation with fragmentation |
| Reclaiming Space | Limited, depends on process termination | Requires defragmentation or compaction |
| Effect on System Performance | May cause inefficient CPU and memory usage | Can cause delays and increased complexity in memory management |
| Typical Use Cases | Embedded systems, fixed-size buffers | Long-running servers, general-purpose OS |
Key Differences
- Internal fragmentation is clearly visible in the wasted space inside allocated memory blocks, whereas external fragmentation is visible in the scattered free space between allocated blocks.
- Internal fragmentation revolves around fixed-size allocations, while external fragmentation involves the overall layout and scattering of free memory.
- Internal fragmentation is more noticeable when memory blocks are significantly larger than needed, causing small unused spaces. Although incomplete. External fragmentation is noticeable when large contiguous free memory is unavailable despite enough total free space.
- External fragmentation relates to the fragmentation of free space, whereas internal fragmentation relates to inefficient use of allocated space, impacting different parts of memory management.
FAQs
How does fragmentation affect virtual memory systems differently than physical memory?
Virtual memory systems can mitigate physical fragmentation by swapping pages in and out, but external fragmentation still impacts the physical RAM. Managing page tables and swapping introduces additional complexity in handling fragmentation issues.
Can modern operating systems completely eliminate internal fragmentation?
While techniques like variable-sized partitions and buddy systems reduce internal waste, some degree of internal fragmentation persists due to fixed overheads or specific allocation strategies. Absolute elimination remains challenging.
What role does memory paging play in reducing external fragmentation?
Paging divides memory into fixed-size pages, which helps eliminate external fragmentation by allowing non-contiguous pages to form a process’s address space. Although incomplete. However, it introduces internal fragmentation within each page.
How does fragmentation influence the design of embedded systems?
Embedded systems prefer fixed-size memory pools to avoid external fragmentation, and allocate memory statically to prevent wastage. Managing internal fragmentation is less critical due to predictable workloads and limited memory.
