Struct perf_event::Counter

pub struct Counter { /* fields omitted */ }

A counter for one kind of kernel or hardware event.

A Counter represents a single performance monitoring counter. You select what sort of event you'd like to count when the Counter is created, then you can enable and disable the counter, call its read method to retrieve the current count, and reset it to zero.

A Counter's value is always a u64.

For example, this counts the number of instructions retired (completed) during a call to println!.

use perf_event::Builder;

fn main() -> std::io::Result<()> {
    let mut counter = Builder::new().build()?;

    let vec = (0..=51).collect::<Vec<_>>();

    counter.enable()?;
    println!("{:?}", vec);
    counter.disable()?;

    println!("{} instructions retired", counter.read()?);

    Ok(())
}

It is often useful to count several different quantities over the same period of time. For example, if you want to measure the average number of clock cycles used per instruction, you must count both clock cycles and instructions retired, for the same range of execution. The Group type lets you enable, disable, read, and reset any number of counters simultaneously.

When a counter is dropped, its kernel resources are freed along with it.

Methods

impl Counter

pub fn id(&self) -> u64

Return this counter's kernel-assigned unique id.

This can be useful when iterating over Counts.

pub fn enable(&mut self) -> Result<()>

Allow this Counter to begin counting its designated event.

This does not affect whatever value the Counter had previously; new events add to the current count. To clear a Counter, use the reset method.

Note that Group also has an enable method, which enables all its member Counters as a single atomic operation.

pub fn disable(&mut self) -> Result<()>

Make this Counter stop counting its designated event. Its count is unaffected.

Note that Group also has a disable method, which disables all its member Counters as a single atomic operation.

pub fn reset(&mut self) -> Result<()>

Reset the value of this Counter to zero.

Note that Group also has a reset method, which resets all its member Counters as a single atomic operation.

pub fn read(&mut self) -> Result<u64>

Return this Counter's current value as a u64.

Note that Group also has a read method, which reads all its member Counters' values at once.

Trait Implementations

impl Debug for Counter

fn fmt(&self, fmt: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<'_> Index<&'_ Counter> for Counts

type Output = u64

The returned type after indexing.

fn index(&self, index: &Counter) -> &u64

Performs the indexing (container[index]) operation.