Orthotope

Orthotope is a Rust allocator library with:

Installation

cargo add orthotope

Features

• a pre-mapped arena
• fixed size classes up to 16 MiB
• per-thread caches
• a shared central pool
• a tracked large-allocation path

It is aimed at allocation-heavy workloads such as ML inference, tensor pipelines, batched embedding or reranking services, and other high-throughput systems.

API

use orthotope::{allocate, deallocate};

let ptr = allocate(128)?;

unsafe {
    deallocate(ptr)?;
}
# Ok::<(), Box<dyn std::error::Error>>(())

• allocate(size) returns Result<NonNull<u8>, AllocError>
• deallocate(ptr) is the primary free path
• deallocate_with_size(ptr, size) validates the recorded size before freeing

Only free live pointers returned by Orthotope. Small-object double free remains undefined behavior.

For direct instance-oriented use, the crate also exposes Allocator, AllocatorConfig, ThreadCache, and SizeClass at the crate root. Use one ThreadCache per thread when calling Allocator::allocate_with_cache or Allocator::deallocate_with_cache directly.

Behavior

• small allocations use thread-local reuse first, then central-pool refill, then arena carving
• small-cache arena refill reserves one contiguous span and splits it locally into class-sized blocks
• frees are routed by a 64-byte allocation header
• requests above 16 MiB use the large-allocation path
• default alignment is 64 bytes
• custom allocator alignment must be a power of two and at least 64 bytes
• the global convenience API uses AllocatorConfig::default()

Small-object provenance in v1 is limited to header validation plus an arena-range ownership check on the decoded block start. Foreign pointers are rejected where detectable, but small-object double free remains undefined behavior and same-arena pointer forgery is not guaranteed to be detected.

Large allocations are also tracked in a live registry. Duplicate large frees are rejected when the pointer still decodes to a valid large-allocation header.

Small-request classes:

• 1..=64
• 65..=256
• 257..=4096
• 4097..=262_144
• 262_145..=1_048_576
• 1_048_577..=16_777_216