rusty_alloc

A pure-Rust remake of mimalloc — the v2.4.5 architecture (32 MiB segments, free-list-sharded pages, lock-free cross-thread frees), rebuilt from the design rather than transliterated from the C.

Status: 0.3.2 — a 0.x release. The API is not frozen; the performance evidence is not yet complete. Read What is and isn't measured before depending on it.

What it is

~150 of mimalloc's ~157 mi_* entry points, semantics-for-semantics.
Safe by default where it counts. A double free is detected and aborted, not silently accepted. Upstream mimalloc does not detect this in release builds; we chose to, at a measured cost of ~0.4% on perl and ~0.2% on sqlite. Handing the same block to two owners is the failure this project exists to prevent, so paying for the check is the point.
No C anywhere in the product. The C mimalloc in this repository is a development-only differential oracle; it is never a dependency and is never published.
Runs on WebAssembly (wasm32-unknown-unknown) via memory.grow, with no C toolchain and no emscripten.

What is and isn't measured

Measured, deterministically, via callgrind instructions retired on x86-64 Linux under LD_PRELOAD:

workload	vs mimalloc	vs glibc
lua	0.99	0.84
perl	1.01	0.83
sqlite	1.00	1.00

That is parity with mimalloc and roughly 16% fewer instructions than glibc.

NOT measured, and therefore not claimed:

Wall-clock time. Every number above counts instructions. Instructions and time are not the same thing, and we have not established that this build is faster in seconds.
The full mimalloc-bench corpus. Three workloads, not the suite.
RSS. No systematic memory-footprint sweep.
aarch64. Code paths exist and compile; they have never been executed.

There is no "faster than mimalloc" claim here, because the evidence for one does not exist yet.

Usage

This crate is the allocator core. For the ergonomic Rust surface (GlobalAlloc, first-class Heap, the Allocator trait), use rusty_alloc_api.

Features

feature	what
`debug_checks`	full invariant validation: list walks, span tiling, page canaries
`secure`	guard pages, encrypted free lists, guarded-object sampling
`profile`	feature-gated path profiler

Statistics counters follow upstream's MI_STAT rule: present in debug builds, compiled out of release.

License