Memory Allocation Demo

Description

Demonstrates different kernel memory allocation methods: kmalloc, vmalloc, and slab caches.

Features

• kmalloc: Fast, physically contiguous (1 KB)
• vmalloc: Large, virtually contiguous (1 MB)
• Slab cache: Efficient for same-size objects
• Memory initialization and cleanup
• Size information reporting

Build & Test

make
sudo insmod memory_demo.ko

# Watch the detailed output
dmesg | tail -30

sudo rmmod memory_demo
dmesg | tail -10

Expected Output

=== Memory Allocation Demo ===

1. Testing kmalloc...
  ✓ kmalloc: Allocated 1024 bytes at 0x...
  ✓ kmalloc: Memory initialized

2. Testing vmalloc...
  ✓ vmalloc: Allocated 1048576 bytes at 0x...
  ✓ vmalloc: Memory initialized

3. Testing slab cache...
  ✓ slab: Cache created
  ✓ slab: Object allocated at 0x...
  ✓ slab: Object initialized (id=42, name=test_object)

4. Memory information:
  - kmalloc size: 1024 bytes
  - PAGE_SIZE: 4096 bytes
  - KMALLOC_MAX_SIZE: ...

=== Memory Demo: All allocations successful ===

Memory Types Comparison

Type	Size Limit	Speed	Physically Contiguous	Use Case
kmalloc	~4MB	Fast	Yes	Small allocations, DMA
vmalloc	Large	Slower	No	Large buffers
Slab	Any	Fast	Depends	Same-size objects

Learning Points

• Different allocation functions for different needs
• Proper cleanup order (reverse of allocation)
• Memory debugging with ksize()
• Slab cache for performance
• Understanding physical vs virtual contiguity