Crate jemalloc_ctl

Expand description

jemalloc control and introspection.

jemalloc offers a powerful introspection and control interface through the mallctl function. It can be used to tune the allocator, take heap dumps, and retrieve statistics. This crate provides a typed API over that interface.

While mallctl takes a string to specify an operation (e.g. stats.allocated or stats.arenas.15.muzzy_decay_ms), the overhead of repeatedly parsing those strings is not ideal. Fortunately, jemalloc offers the ability to translate the string ahead of time into a “Management Information Base” (MIB) to speed up future lookups.

This crate provides a type for each mallctl operation. Calling $op::{read(), write(x), update(x)} on the type calls mallctl with the string-based API. If the operation will be repeatedly performed, a MIB for the operation can be obtained using $op.mib().

Examples

Repeatedly printing allocation statistics:

use std::thread;
use std::time::Duration;
use jemalloc_ctl::{stats, epoch};

#[global_allocator]
static ALLOC: jemallocator::Jemalloc = jemallocator::Jemalloc;

fn main() {
    loop {
        // many statistics are cached and only updated when the epoch is advanced.
        epoch::advance().unwrap();

        let allocated = stats::allocated::read().unwrap();
        let resident = stats::resident::read().unwrap();
        println!("{} bytes allocated/{} bytes resident", allocated, resident);
        thread::sleep(Duration::from_secs(10));
    }
}

Doing the same with the MIB-based API:

use std::thread;
use std::time::Duration;
use jemalloc_ctl::{stats, epoch};

#[global_allocator]
static ALLOC: jemallocator::Jemalloc = jemallocator::Jemalloc;

fn main() {
    let e = epoch::mib().unwrap();
    let allocated = stats::allocated::mib().unwrap();
    let resident = stats::resident::mib().unwrap();
    loop {
        // many statistics are cached and only updated when the epoch is advanced.
        e.advance().unwrap();

        let allocated = allocated.read().unwrap();
        let resident = resident.read().unwrap();
        println!("{} bytes allocated/{} bytes resident", allocated, resident);
        thread::sleep(Duration::from_secs(10));
    }
}