Advanced Memory Allocation Implementation

Advanced Memory Allocation Implementation Visually

Discover how operating systems efficiently manage memory through various allocation strategies. Learn about fixed and dynamic partitioning, fragmentation handling, and advanced memory management techniques that optimize system performance.

Dynamic Partitioning Fixed Partitioning Fragmentation Compaction Virtual Memory Paging & Segmentation First Fit Best Fit Worst Fit Buddy System

Fundamental Principles

Core concepts that explain how memory allocation works

Fixed Partitioning

Memory is divided into fixed-size partitions before execution begins. Each partition can hold exactly one process, leading to internal fragmentation but simple management.

Characteristics:

• Predefined partition sizes

• Simple allocation/deallocation

• Internal fragmentation

• Degree of multiprogramming is fixed

Dynamic Partitioning

Memory partitions are created dynamically as processes arrive. Partitions are exactly sized to fit each process, eliminating internal fragmentation but causing external fragmentation.

Characteristics:

• Variable partition sizes

• No internal fragmentation

• External fragmentation

• Requires compaction

Key Allocation Strategies

Primary algorithms used for memory allocation decisions

First Fit

Allocates the first free block that is large enough to accommodate the process request. Fast but may lead to increased fragmentation over time.

Algorithm: Scan from beginning, allocate first suitable block

Best Fit

Searches the entire list and allocates the smallest free block that can accommodate the process. Minimizes wasted space but slower performance.

Algorithm: Find smallest suitable block

Worst Fit

Allocates the largest available free block. Reduces the number of very small fragments but may waste large amounts of memory.

Algorithm: Allocate largest available block

Next Fit

Similar to first fit but starts searching from where the last allocation left off, rather than from the beginning of the list.

Algorithm: Continue from last allocation point

Buddy System

Divides memory into partitions of sizes that are powers of 2. When a request arrives, the system finds the smallest power-of-2 partition that fits.

Partition sizes: 2^n where n = 0, 1, 2, 3...

Slab Allocation

Pre-allocates memory for frequently used objects in caches. Reduces fragmentation and improves allocation performance for kernel objects.

Cache-based allocation for kernel objects

Fragmentation Types

Understanding memory wastage in different allocation schemes

Internal Fragmentation

Occurs in fixed partitioning when allocated memory is larger than requested memory. The unused portion within the partition represents wasted memory.

Formula: Internal Fragmentation = Partition Size - Process Size

Example: 16KB partition allocated to 12KB process = 4KB internal fragmentation

External Fragmentation

Occurs in dynamic partitioning when free memory is scattered in small blocks that individually cannot satisfy allocation requests despite having sufficient total free space.

Solution: Memory compaction, paging, or segmentation

Impact: Reduces effective memory utilization over time

Advanced Memory Management

Modern techniques for efficient memory utilization

Paging

  • Divides memory into fixed-size pages
  • Eliminates external fragmentation
  • Allows non-contiguous allocation
  • Uses page tables for address translation
  • Enables virtual memory implementation

Segmentation

  • Divides memory into logical segments
  • Supports modular programming
  • Provides protection boundaries
  • Allows sharing of segments
  • Can combine with paging (segmented paging)

Virtual Memory

  • Separates logical from physical memory
  • Allows processes larger than physical RAM
  • Uses demand paging
  • Implements page replacement algorithms
  • Provides memory protection

Memory Allocation rGE

Interactive tools to calculate memory allocation metrics

Fragmentation Calculator

Calculate internal and external fragmentation in different allocation schemes

Results:

Internal Fragmentation: 0 MB

External Fragmentation: 0 MB

Memory Utilization: 100%

Wasted Memory: 0 MB

Allocation Efficiency Calculator

Compare efficiency of different allocation algorithms

Results:

Successfully Allocated: 0 processes

Total Allocated Memory: 0 MB

Remaining Free Memory: 0 MB

Efficiency Ratio: 0%

Unit Converters

Convert between different memory units commonly used in allocation calculations

Memory Unit Converter

Convert between different memory units

Result: 1

Address Translation Converter

Convert between logical and physical addresses

Physical Address: 20480

Page Number: 1

Offset: 0

Export and Import Options

Save and share your memory allocation simulations and data with proper implementations

Export Data

Save your simulation results and uvw

Import Data

Load previously saved memory allocation data and uvw

Interactive Simulations

Explore memory allocation through hands-on uvw

Dynamic Partitioning Simulation

Visualize how memory is allocated and deallocated dynamically

100 MB
Medium

Step 1: Initial memory state with 100MB total capacity.

Fragmentation Visualization

Experience how fragmentation develops over time in dynamic allocation

60 seconds
30%

Step 1: Memory starts with uniform allocation.

Difference with Other Related Fields

How Memory Allocation differs from other computer science concepts

Memory Allocation vs. Memory Management

  • Memory Allocation: Process of assigning memory blocks to processes
  • Memory Management: Broader concept including allocation, deallocation, and optimization
  • Allocation is a subset of management
  • Management includes garbage collection, virtual memory
  • Allocation focuses on placement strategies
  • Management considers system-wide optimization

Memory Allocation vs. Storage Management

  • Memory Allocation: Manages volatile RAM for running processes
  • Storage Management: Manages persistent storage devices
  • Memory is fast but temporary
  • Storage is slow but permanent
  • Memory allocation uses algorithms like First Fit
  • Storage management uses file allocation methods

Memory Allocation vs. CPU Scheduling

  • Memory Allocation: Assigns memory resources to processes
  • CPU Scheduling: Determines which process gets CPU time
  • Both are resource management techniques
  • Memory allocation affects process execution
  • CPU scheduling affects process timing
  • Work together for system optimization

Exercise Examples

Practice problems with solutions to reinforce understanding

Problem:

A system has fixed partitions of 16KB each. Processes of sizes 12KB, 8KB, 20KB, and 6KB arrive. Calculate the total internal fragmentation.

Solution:

For each process:

• 12KB process: 16KB - 12KB = 4KB fragmentation

• 8KB process: 16KB - 8KB = 8KB fragmentation

• 20KB process: Cannot fit in 16KB partition (external fragmentation)

• 6KB process: 16KB - 6KB = 10KB fragmentation

Total internal fragmentation = 4 + 8 + 10 = 22KB

Answer:

Total internal fragmentation is 22KB.

Problem:

In a dynamic partitioning system, memory holes of sizes 10KB, 4KB, 20KB, 18KB, 7KB, 9KB, 12KB, and 15KB exist. A new process of 12KB arrives. Show allocation using First Fit, Best Fit, and Worst Fit.

Solution:

First Fit: Allocates first hole ≥ 12KB = 20KB hole
Fragmentation = 20KB - 12KB = 8KB

Best Fit: Finds smallest hole ≥ 12KB = 12KB hole
Fragmentation = 12KB - 12KB = 0KB

Worst Fit: Allocates largest available hole = 20KB hole
Fragmentation = 20KB - 12KB = 8KB

Answer:

Best Fit produces zero fragmentation, while First Fit and Worst Fit both produce 8KB fragmentation.

Problem:

In a paged memory system with 4KB pages, given a logical address of 8196, find the page number and offset. If the page is mapped to frame 7, what is the physical address?

Solution:

Page size = 4KB = 4096 bytes

Page number = Logical address ÷ Page size = 8196 ÷ 4096 = 2 (integer division)

Offset = Logical address mod Page size = 8196 mod 4096 = 8196 - (2 × 4096) = 8196 - 8192 = 4

Physical address = (Frame number × Page size) + Offset = (7 × 4096) + 4 = 28672 + 4 = 28676

Answer:

Page number = 2, Offset = 4, Physical address = 28676

Multiple Choice Questions

Test your understanding of Memory Allocation concepts

1. Which memory allocation method eliminates external fragmentation?

Correct Answer: c) Paging

Paging eliminates external fragmentation by dividing memory into fixed-size pages and allowing non-contiguous allocation.

2. What is internal fragmentation?

Correct Answer: a) Unused space within allocated blocks

Internal fragmentation occurs in fixed partitioning when allocated memory is larger than the requested amount.

3. Which algorithm produces the least fragmentation?

Correct Answer: b) Best Fit

Best Fit minimizes fragmentation by finding the smallest block that can accommodate the request.

4. What is the main disadvantage of fixed partitioning?

Correct Answer: b) Internal fragmentation

Fixed partitioning causes internal fragmentation because partitions are often larger than the processes they contain.

5. In paging, what determines the page size?

Correct Answer: d) All of the above

Page size is determined by hardware capabilities, OS design choices, and application requirements.

6. What is memory compaction used for?

Correct Answer: c) Reduce external fragmentation

Memory compaction moves allocated blocks together to create larger contiguous free spaces, reducing external fragmentation.