llogiq / Flamer

A proc macro to insert appropriate flame::start_guard(_) calls (for use with flame)

This proc macro requires Rust 1.30. Because flamer is a proc macro attribute, it uses APIs stabilized in Rust 1.30.

Usage:

In your Cargo.toml add flame and flamer to your dependencies:

[dependencies]
flame = "0.2.2"
flamer = "0.3"

Then in your crate root, add the following:

extern crate flame;
#[macro_use] extern crate flamer;

#[flame]
// The item to apply `flame` to goes here.

Unfortunately, currently stable Rust doesn't allow custom attributes on modules. To use #[flame] on modules you need a nightly Rust with #![feature(proc_macro_hygiene)] in the crate root (related issue):

#![feature(proc_macro_hygiene)]

extern crate flame;
#[macro_use] extern crate flamer;

#[flame]
mod flamed_module { .. }

You may also opt for an optional dependency. In that case your Cargo.toml should have:

[dependencies]
flame = { version = "0.2.2", optional = true }
flamer = { version = "0.3", optional = true }

[features]
default = []
flame_it = ["flame", "flamer"]

And your crate root should contain:

#[cfg(feature = "flame_it")]
extern crate flame;
#[cfg(feature = "flame_it")]
#[macro_use] extern crate flamer;

// as well as the following instead of `#[flame]`
#[cfg_attr(feature = "flame_it", flame)]
// The item to apply `flame` to goes here.

For nightly module support, also add #![cfg_attr(feature = "flame_it", feature(proc_macro_hygiene))] in the crate root:

#![cfg_attr(feature = "flame_it", feature(proc_macro_hygiene))]

#[cfg(feature = "flame_it")]
extern crate flame;
#[cfg(feature = "flame_it")]
#[macro_use] extern crate flamer;

// as well as the following instead of `#[flame]`
#[cfg_attr(feature = "flame_it", flame)]
mod flamed_module { .. }

You should then be able to annotate every item (alas, currently not the whole crate; see the custom inner attribute issue for more details) with #[flame] annotations. You can also use #[noflame] annotations to disable instrumentations for subitems of #[flame]d items. Note that this only instruments the annotated methods, it does not print out the results.

The flame annotation can also take an optional parameter specifying a string to prefix to enclosed method names. This is especially useful when annotating multiple methods with the same name, but in different modules.

#[flame("prefix")]
fn method_name() {
    //The corresponding block on the flamegraph will be named "prefix::method_name"
}

Full Example

use std::fs::File;

use flame as f;
use flamer::flame;

#[flame]
fn make_vec(size: usize) -> Vec<u32> {
    // using the original lib is still possible
    let mut res = f::span_of("vec init", || vec![0_u32; size]);
    for x in 0..size {
        res[x] = ((x + 10)/3) as u32;
    }
    let mut waste_time = 0;
    for i in 0..size*10 {
        waste_time += i
    }
    res
}
#[flame]
fn more_computing(i: usize) {
    for x in 0..(i * 100) {
        let mut v = make_vec(x);
        let x = Vec::from(&v[..]);
        for i in 0..v.len() {
            let flip = (v.len() - 1) - i as usize;
            v[i] = x[flip];
        }
    }
}
#[flame]
fn some_computation() {
    for i in 0..15 {
        more_computing(i);
    }
}

#[flame]
fn main() {
    some_computation();
    // in order to create the flamegraph you must call one of the
    // flame::dump_* functions.
    f::dump_html(File::create("flamegraph.html").unwrap()).unwrap();
}

Refer to flame's documentation to see how output works.

License: Apache 2.0