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https://github.com/yazaldefilimone/tlsf_allocator.rs
Two level segregated fit memory allocator
https://github.com/yazaldefilimone/tlsf_allocator.rs
allocator memory rust
Last synced: about 1 month ago
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Two level segregated fit memory allocator
- Host: GitHub
- URL: https://github.com/yazaldefilimone/tlsf_allocator.rs
- Owner: yazaldefilimone
- Created: 2024-05-17T19:23:44.000Z (6 months ago)
- Default Branch: main
- Last Pushed: 2024-06-10T09:14:23.000Z (5 months ago)
- Last Synced: 2024-10-12T05:11:51.430Z (about 1 month ago)
- Topics: allocator, memory, rust
- Language: Rust
- Homepage:
- Size: 10.7 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: readme.md
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README
### SpeedAllocator Overview
The Two-Level Segregated Fit (SpeedAllocator) allocator is designed for real-time systems, providing constant and predictable response times for memory allocation and deallocation, while minimizing fragmentation.
#### Key Features
1. **Two-Level Segregated Free Lists**:
- **First-Level Index (FLI)**: Divides memory blocks into size classes that are powers of two (e.g., 16, 32, 64 bytes).
- **Second-Level Index (SLI)**: Subdivides each first-level class into smaller size ranges to reduce fragmentation.
2. **Block Header**:
- `size`: Size of the block.
- `prev_phys_block`: Pointer to the previous physical block.
- `next_free`: Pointer to the next free block in the free list.
- `prev_free`: Pointer to the previous free block in the free list.
- `is_free`: Indicates if the block is free.
- `is_last`: Indicates if this is the last block in the memory pool.
3. **Bitmaps**: Used to quickly locate non-empty free lists, optimizing search operations.
SpeedAllocator Structure Diagram
```
| SpeedAllocator Structure |
|____________________________|
| |
| First-Level Array (FLI) |
| ________________________ |
| | | | | | |
| | FLI | FLI | ... | FLI | |
|_|_____|_____|_____|_____|__|
| | | |
v v v v
|____________________________|
| Second-Level Array (SLI) |
| ________________________ |
| | SLI | SLI | ... | SLI | |
|_|_____|_____|_____|_____|__|
| | | |
v v v v
|____________________________|
| Free Lists |
| ________________________ |
| | blk | blk | ... | blk | |
|_|_____|_____|_____|_____|__|
```
Each entry in the first-level array points to a second-level array, which in turn contains lists of free memory blocks. The combination of these arrays allows for efficient management and quick access to free blocks of various sizes.
#### Basic Operations
1. **Allocation (`allocate`)**:
- Find a suitable free block using the first and second-level indices.
- Split the block if necessary.
- Update the free lists and bitmaps accordingly.
2. **Deallocation (`deallocate`)**:
- Mark the block as free.
- Coalesce (merge) with adjacent free blocks if possible.
- Insert the block back into the appropriate free list and update the bitmaps.
#### How It Works
1. **Mapping Function**: Determines the first and second-level indices based on the size of the block.
2. **Insert Free Block**: Adds a block to the appropriate free list.
3. **Remove Free Block**: Removes a block from the free list.
4. **Coalescing**: Merges adjacent free blocks to reduce fragmentation.
The SpeedAllocator is efficient and predictable, making it suitable for real-time systems where predictable behavior and performance are critical. The use of two-level segregated lists and bitmaps ensures fast and constant-time operations for both allocation and deallocation.
## Research Paper
- [Two-Level Segregated Fit Allocator](http://www.gii.upv.es/tlsf/files/papers/ecrts04_tlsf.pdf)