mimalloc-pprof

mimalloc as a Rust global allocator, with pprof-compatible sampled heap profiling built in. Windows is a first-class target alongside Linux and macOS.

Dumps open directly in google/pprof for flame graphs, call graphs, top reports, and profile diffs.

Usage

[dependencies]
mimalloc-pprof = "0.9"

[profile.release]
debug = "line-tables-only"
strip = false

use mimalloc_pprof::{prof, MiMalloc};
use std::path::Path;

#[global_allocator]
static ALLOCATOR: MiMalloc = MiMalloc;

fn main() -> std::io::Result<()> {
    assert!(prof::start(0), "profiler already running"); // 0 = default, ~512 KiB

    let retained = vec![0_u8; 1024 * 1024];
    prof::dump_file(Path::new("heap.prof"))?;            // dump while still live
    std::hint::black_box(&retained);

    prof::stop();
    Ok(())
}

Then:

pprof -http=:0 ./target/release/my_app heap.prof

Or profile without touching the code at all:

MIMALLOC_PROF=1 MIMALLOC_PROF_DUMP_AT_EXIT=heap.prof ./my_app

Versions

	crate	engine
0.9.x — current	`mimalloc-pprof = "0.9"`	mimalloc v3
0.8.x — previous	`mimalloc-pprof = "0.8"`	mimalloc v2

The profiler API, environment variables, and output formats are identical in both, so moving between them is a version bump rather than a code change.

0.9.x is recommended. It has strictly more test coverage, per-heap allocator statistics, and fixes two upstream mimalloc bugs that 0.8.x still carries — including an unbounded memory leak on Windows/MinGW where every exiting thread leaked its heap and pages (23.5 GB at 100 stress iterations, versus flat after the fix). Note that upstream mimalloc v3 is itself still a pre-release branch.

Exact statistics alongside sampled ones

On 0.9.x, prof::stats() carries the allocator's exact counters next to the sampled ones. A sampled profile alone cannot tell you whether it under-counted; comparing the two measures the sampling error directly:

let s = mimalloc_pprof::prof::stats();
println!(
    "sampled live: {} bytes in {} samples; allocator committed: {}, requested: {}",
    s.live_bytes, s.live_samples, s.heap.committed, s.heap.malloc_requested,
);

Notes

On Linux and macOS, keep frame pointers for reliable stack walking: rustflags = ["-Cforce-frame-pointers=yes"] in .cargo/config.toml. Windows x64 uses unwind information instead — keep the PDB.
Do not link a second mimalloc into the same process; this crate vendors its own.

Full documentation, the C API, and the upstream-bug details are in the repository README.

License