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//! `Perf` measures the selected perf events using the perf interface of the Linux kernel.
//!
//! # Example
//!
//! ```rust
//! extern crate criterion_perf_events;
//! extern crate perfcnt;
//!
//! # fn fibonacci_slow(_: usize) {}
//! # fn fibonacci_fast(_: usize) {}
//!
//! use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion};
//! use criterion_perf_events::Perf;
//! use perfcnt::linux::HardwareEventType as Hardware;
//! use perfcnt::linux::PerfCounterBuilderLinux as Builder;
//!
//! fn bench(c: &mut Criterion<Perf>) {
//! let mut group = c.benchmark_group("fibonacci");
//!
//! for i in 0..20 {
//! group.bench_function(BenchmarkId::new("slow", i), |b| b.iter(|| fibonacci_slow(i)));
//! group.bench_function(BenchmarkId::new("fast", i), |b| b.iter(|| fibonacci_fast(i)));
//! }
//!
//! group.finish()
//! }
//!
//! criterion_group!(
//! name = my_bench;
//! config = Criterion::default().with_measurement(Perf::new(Builder::from_hardware_event(Hardware::CacheMisses)));
//! targets = bench
//! );
//! criterion_main!(my_bench);
//! ```
extern crate perfcnt;
use criterion::{
measurement::{Measurement, ValueFormatter},
Throughput,
};
use std::cell::RefCell;
use perfcnt::linux::PerfCounter;
use perfcnt::linux::PerfCounterBuilderLinux;
use perfcnt::AbstractPerfCounter;
/// `perf` implements `criterion::measurement::Measurement` so it can be used in criterion to measure perf events.
/// Create a struct via `Perf::new()`.
pub struct Perf {
counter: RefCell<PerfCounter>,
}
impl Perf {
/// Creates a new criterion measurement plugin that measures perf events.
///
/// # Argument
///
/// * `builder` - A PerfCounterBuilderLinux from the crate perfcnt that is configured for the selected counter.
///
/// # Remarks
///
/// Should only fail if you select a counter that is not available on your system or you do not have the necessarry access rights.
pub fn new(mut builder: PerfCounterBuilderLinux) -> Perf {
Perf {
counter: RefCell::new(
builder
.for_pid(std::process::id() as i32)
.disable()
.finish()
.expect("Could not create counter"),
),
}
}
}
impl Measurement for Perf {
type Intermediate = u64;
type Value = u64;
fn start(&self) -> Self::Intermediate {
self.counter
.borrow()
.start()
.expect("Could not read perf counter");
0
}
fn end(&self, _i: Self::Intermediate) -> Self::Value {
self.counter
.borrow()
.stop()
.expect("Could not stop perf counter");
let ret = self
.counter
.borrow_mut()
.read()
.expect("Could not read perf counter");
self.counter
.borrow_mut()
.reset()
.expect("Could not reset perf counter");
ret
}
fn add(&self, v1: &Self::Value, v2: &Self::Value) -> Self::Value {
v1 + v2
}
fn zero(&self) -> Self::Value {
0
}
fn to_f64(&self, value: &Self::Value) -> f64 {
*value as f64
}
fn formatter(&self) -> &dyn ValueFormatter {
&PerfFormatter
}
}
struct PerfFormatter;
impl ValueFormatter for PerfFormatter {
fn format_value(&self, value: f64) -> String {
format!("{value:.4} cycles")
}
fn format_throughput(&self, throughput: &Throughput, value: f64) -> String {
match throughput {
Throughput::Bytes(bytes) => format!("{:.4} events/byte", value / *bytes as f64),
Throughput::BytesDecimal(bytes) => {
let event_per_byte = value / *bytes as f64;
let (denominator, unit) = if *bytes < 1000 {
(1.0, "events/byte")
} else if *bytes < 1000 * 1000 {
(1000.0, "events/kilobyte")
} else if *bytes < 1000 * 1000 * 1000 {
(1000.0 * 1000.0, "events/megabyte")
} else {
(1000.0 * 1000.0 * 1000.0, "events/gigabyte")
};
format!("{:.4} {}", event_per_byte / denominator, unit)
}
Throughput::Elements(bytes) => format!("{:.4} events/element", value / *bytes as f64),
}
}
fn scale_values(&self, _typical_value: f64, _values: &mut [f64]) -> &'static str {
"events"
}
fn scale_throughputs(
&self,
_typical_value: f64,
throughput: &Throughput,
values: &mut [f64],
) -> &'static str {
match throughput {
Throughput::Bytes(bytes) => {
for val in values {
*val /= *bytes as f64;
}
"events/byte"
}
Throughput::BytesDecimal(bytes) => {
let bytes_per_second = *bytes;
let (denominator, unit) = if bytes_per_second < 1000 {
(1.0, "events/byte")
} else if bytes_per_second < 1000 * 1000 {
(1000.0, "events/kilobyte")
} else if bytes_per_second < 1000 * 1000 * 1000 {
(1000.0 * 1000.0, "events/megabyte")
} else {
(1000.0 * 1000.0 * 1000.0, "events/gigabyte")
};
for val in values {
*val /= *bytes as f64;
*val /= denominator;
}
unit
}
Throughput::Elements(bytes) => {
for val in values {
*val /= *bytes as f64;
}
"events/element"
}
}
}
fn scale_for_machines(&self, _values: &mut [f64]) -> &'static str {
"events"
}
}