better_mimalloc_rs

A drop-in global allocator wrapper around the mimalloc allocator. This fork exposes tuning knobs for RSS behavior and tracks the mimalloc dev branch (more aggressive than release).

Why "better"

• More tunable: upstream Rust bindings expose very few knobs. This crate exposes compile-time and runtime options so you can tune purging/commit behavior and make RSS fall back faster.
• Tracks dev branch: follows the latest mimalloc development branch for newer fixes and behavior (expect churn).

Usage

use better_mimalloc_rs::MiMalloc;

#[global_allocator]
static GLOBAL: MiMalloc = MiMalloc;

RSS tuning (config feature)

Enable the config feature to expose runtime/compile-time tuning:

[dependencies]
better_mimalloc_rs = { version = "*", features = ["config"] }

Apply compile-time defaults:

use better_mimalloc_rs::MiMalloc;

#[global_allocator]
static GLOBAL: MiMalloc = MiMalloc;

fn main() {
    MiMalloc::init();
    // ...
}

Apply runtime overrides:

use better_mimalloc_rs::{MiMalloc, MiMallocConfig};

#[global_allocator]
static GLOBAL: MiMalloc = MiMalloc;

fn main() {
    let cfg = MiMallocConfig {
        purge_delay: Some(0),
        purge_decommits: Some(true),
        ..MiMallocConfig::default()
    };
    MiMalloc::init_with(&cfg);
}

Call MiMalloc::init()/init_with() before any allocations for deterministic behavior.

Compile-time environment variables (optional):

MIMALLOC_CFG_EAGER_COMMIT=0|1
MIMALLOC_CFG_EAGER_COMMIT_DELAY=NUM
MIMALLOC_CFG_ARENA_EAGER_COMMIT=NUM
MIMALLOC_CFG_PURGE_DECOMMITS=0|1
MIMALLOC_CFG_PURGE_DELAY=NUM
MIMALLOC_CFG_ARENA_PURGE_MULT=NUM
MIMALLOC_CFG_PURGE_EXTEND_DELAY=NUM
MIMALLOC_CFG_GENERIC_COLLECT=NUM

Using the forked mimalloc source

This repo expects the C sources under libmimalloc-sys/c_src/mimalloc. Initialize the submodule after cloning:

git submodule update --init --recursive

If you keep the sources elsewhere, set MIMALLOC_SRC to the root of that checkout:

export MIMALLOC_SRC=/path/to/acking-you/mimalloc

Requirements

A C compiler is required for building mimalloc with cargo.

Usage with secure mode

Using secure mode adds guard pages, randomized allocation, encrypted free lists, etc. The performance penalty is usually around 10% according to mimalloc's own benchmarks.

To enable secure mode, put in Cargo.toml:

[dependencies]
better_mimalloc_rs = { version = "*", features = ["secure"] }