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//! A performance monitoring API for Linux.
//!
//! This crate provides access to processor and kernel counters for things like
//! instruction completions, cache references and misses, branch predictions,
//! context switches, page faults, and so on.
//!
//! For example, to compare the number of clock cycles elapsed with the number
//! of instructions completed during one call to `println!`:
//!
//! use perf_event::{Builder, Group};
//! use perf_event::events::Hardware;
//!
//! fn main() -> std::io::Result<()> {
//! // A `Group` lets us enable and disable several counters atomically.
//! let mut group = Group::new()?;
//! let cycles = Builder::new().group(&mut group).kind(Hardware::CPU_CYCLES).build()?;
//! let insns = Builder::new().group(&mut group).kind(Hardware::INSTRUCTIONS).build()?;
//!
//! let vec = (0..=51).collect::<Vec<_>>();
//!
//! group.enable()?;
//! println!("{:?}", vec);
//! group.disable()?;
//!
//! let counts = group.read()?;
//! println!("cycles / instructions: {} / {} ({:.2} cpi)",
//! counts[&cycles],
//! counts[&insns],
//! (counts[&cycles] as f64 / counts[&insns] as f64));
//!
//! Ok(())
//! }
//!
//! This crate is built on top of the Linux [`perf_event_open`][man] system
//! call; that documentation has the authoritative explanations of exactly what
//! all the counters mean.
//!
//! There are two main types for measurement:
//!
//! - A [`Counter`] is an individual counter. Use [`Builder`] to
//! construct one.
//!
//! - A [`Group`] is a collection of counters that can be enabled and
//! disabled atomically, so that they cover exactly the same period of
//! execution, allowing meaningful comparisons of the individual values.
//!
//! If you're familiar with the kernel API already:
//!
//! - A `Builder` holds the arguments to a `perf_event_open` call:
//! a `struct perf_event_attr` and a few other fields.
//!
//! - `Counter` and `Group` objects are just event file descriptors, together
//! with their kernel id numbers, and some other details you need to
//! actually use them. They're different types because they yield different
//! types of results, and because you can't retrieve a `Group`'s counts
//! without knowing how many members it has.
//!
//! ### Call for PRs
//!
//! Linux's `perf_event_open` API can report all sorts of things this crate
//! doesn't yet understand: stack traces, logs of executable and shared library
//! activity, tracepoints, kprobes, uprobes, and so on. And beyond the counters
//! in the kernel header files, there are others that can only be found at
//! runtime by consulting `sysfs`, specific to particular processors and
//! devices. For example, modern Intel processors have counters that measure
//! power consumption in Joules.
//!
//! If you find yourself in need of something this crate doesn't support, please
//! consider submitting a pull request.
//!
//! [man]: http://man7.org/linux/man-pages/man2/perf_event_open.2.html
#![deny(missing_docs)]
use events::Event;
use libc::pid_t;
use perf_event_open_sys::bindings::perf_event_attr;
use std::fs::File;
use std::io::{self, Read};
use std::os::raw::{c_int, c_uint, c_ulong};
use std::os::unix::io::{AsRawFd, FromRawFd};
pub mod events;
#[cfg(feature = "hooks")]
pub mod hooks;
// When the `"hooks"` feature is not enabled, call directly into
// `perf-event-open-sys`.
#[cfg(not(feature = "hooks"))]
use perf_event_open_sys as sys;
// When the `"hooks"` feature is enabled, `sys` functions allow for
// interposed functions that provide simulated results for testing.
#[cfg(feature = "hooks")]
use hooks::sys;
/// 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.
///
/// Internally, a `Counter` is just a wrapper around an event file descriptor.
///
/// [`read`]: Counter::read
pub struct Counter {
/// The file descriptor for this counter, returned by `perf_event_open`.
///
/// When a `Counter` is dropped, this `File` is dropped, and the kernel
/// removes the counter from any group it belongs to.
file: File,
/// The unique id assigned to this counter by the kernel.
id: u64,
}
/// A builder for [`Counter`]s.
///
/// There are dozens of parameters that influence a `Counter`'s behavior.
/// `Builder` lets you construct a `Counter` by specifying only those parameters
/// for which you don't want the default value.
///
/// A freshly built `Counter` is disabled. To begin counting events, you must
/// call [`enable`] on the `Counter` or the `Group` to which it belongs.
///
/// For example, if you want a `Counter` for instructions retired by the current
/// process, those are `Builder`'s defaults, so you need only write:
///
/// # use perf_event::Builder;
/// # fn main() -> std::io::Result<()> {
/// let mut insns = Builder::new().build()?;
/// # Ok(()) }
///
/// The [`kind`] method lets you specify what sort of event you want to
/// count. So if you'd rather count branch instructions:
///
/// # use perf_event::Builder;
/// # use perf_event::events::Hardware;
/// # fn main() -> std::io::Result<()> {
/// let mut insns = Builder::new()
/// .kind(Hardware::BRANCH_INSTRUCTIONS)
/// .build()?;
/// # Ok(()) }
///
/// The [`group`] method lets you gather individual counters into `Group`
/// that can be enabled or disabled atomically:
///
/// # use perf_event::{Builder, Group};
/// # use perf_event::events::Hardware;
/// # fn main() -> std::io::Result<()> {
/// let mut group = Group::new()?;
/// let cycles = Builder::new().group(&mut group).kind(Hardware::CPU_CYCLES).build()?;
/// let insns = Builder::new().group(&mut group).kind(Hardware::INSTRUCTIONS).build()?;
/// # Ok(()) }
///
/// Other methods let you select:
///
/// - specific processes or cgroups to observe
/// - specific CPU cores to observe
///
/// `Builder` supports only a fraction of the many knobs and dials Linux offers,
/// but hopefully it will acquire methods to support more of them as time goes
/// on.
///
/// Internally, a `Builder` is just a wrapper around the kernel's `struct
/// perf_event_attr` type.
///
/// [`enable`]: Counter::enable
/// [`kind`]: Builder::kind
/// [`group`]: Builder::group
pub struct Builder<'a> {
attrs: perf_event_attr,
who: EventPid<'a>,
cpu: Option<usize>,
group: Option<&'a mut Group>,
}
#[derive(Debug)]
enum EventPid<'a> {
/// Monitor the calling process.
ThisProcess,
/// Monitor the given pid.
Other(pid_t),
/// Monitor members of the given cgroup.
CGroup(&'a File),
}
/// A group of counters that can be managed as a unit.
///
/// A `Group` represents a group of [`Counter`]s that can be enabled,
/// disabled, reset, or read as a single atomic operation. This is necessary if
/// you want to compare counter values, produce ratios, and so on, since those
/// operations are only meaningful on counters that cover exactly the same
/// period of execution.
///
/// A `Counter` is placed in a group when it is created, by calling the
/// `Builder`'s [`group`] method. A `Group`'s [`read`] method returns values
/// of all its member counters at once as a [`Counts`] value, which can be
/// indexed by `Counter` to retrieve a specific value.
///
/// For example, the following program computes the average number of cycles
/// used per instruction retired for a call to `println!`:
///
/// # fn main() -> std::io::Result<()> {
/// use perf_event::{Builder, Group};
/// use perf_event::events::Hardware;
///
/// let mut group = Group::new()?;
/// let cycles = Builder::new().group(&mut group).kind(Hardware::CPU_CYCLES).build()?;
/// let insns = Builder::new().group(&mut group).kind(Hardware::INSTRUCTIONS).build()?;
///
/// let vec = (0..=51).collect::<Vec<_>>();
///
/// group.enable()?;
/// println!("{:?}", vec);
/// group.disable()?;
///
/// let counts = group.read()?;
/// println!("cycles / instructions: {} / {} ({:.2} cpi)",
/// counts[&cycles],
/// counts[&insns],
/// (counts[&cycles] as f64 / counts[&insns] as f64));
/// # Ok(()) }
///
/// The lifetimes of `Counter`s and `Group`s are independent: placing a
/// `Counter` in a `Group` does not take ownership of the `Counter`, nor must
/// the `Counter`s in a group outlive the `Group`. If a `Counter` is dropped, it
/// is simply removed from its `Group`, and omitted from future results. If a
/// `Group` is dropped, its individual counters continue to count.
///
/// Enabling or disabling a `Group` affects each `Counter` that belongs to it.
/// Subsequent reads from the `Counter` will not reflect activity while the
/// `Group` was disabled, unless the `Counter` is re-enabled individually.
///
/// A `Group` and its members must all observe the same tasks and cpus; mixing
/// these makes building the `Counter` return an error. Unfortunately, there is
/// no way at present to specify a `Group`'s task and cpu, so you can only use
/// `Group` on the calling task. If this is a problem, please file an issue.
///
/// Internally, a `Group` is just a wrapper around an event file descriptor.
///
/// ## Limits on group size
///
/// Hardware counters are implemented using special-purpose registers on the
/// processor, of which there are only a fixed number. (For example, an Intel
/// high-end laptop processor from 2015 has four such registers per virtual
/// processor.) Without using groups, if you request more hardware counters than
/// the processor can actually support, a complete count isn't possible, but the
/// kernel will rotate the processor's real registers amongst the measurements
/// you've requested to at least produce a sample.
///
/// But since the point of a counter group is that its members all cover exactly
/// the same period of time, this tactic can't be applied to support large
/// groups. If the kernel cannot schedule a group, its counters remain zero. I
/// think you can detect this situation by comparing the group's [`time_enabled`]
/// and [`time_running`] values. It might also be useful to set the `pinned` bit,
/// which puts the counter in an error state if it's not able to be put on the
/// CPU; see [#10].
///
/// According to the `perf_list(1)` man page, you may be able to free up a
/// hardware counter by disabling the kernel's NMI watchdog, which reserves one
/// for detecting kernel hangs:
///
/// ```ignore
/// $ echo 0 > /proc/sys/kernel/nmi_watchdog
/// ```
///
/// You can reenable the watchdog when you're done like this:
///
/// ```ignore
/// $ echo 1 > /proc/sys/kernel/nmi_watchdog
/// ```
///
/// [`group`]: Builder::group
/// [`read`]: Group::read
/// [`#5`]: https://github.com/jimblandy/perf-event/issues/5
/// [`#10`]: https://github.com/jimblandy/perf-event/issues/10
/// [`time_enabled`]: Counts::time_enabled
/// [`time_running`]: Counts::time_running
pub struct Group {
/// The file descriptor for this counter, returned by `perf_event_open`.
/// This counter itself is for the dummy software event, so it's not
/// interesting.
file: File,
/// The unique id assigned to this group by the kernel. We only use this for
/// assertions.
id: u64,
/// An upper bound on the number of Counters in this group. This lets us
/// allocate buffers of sufficient size for for PERF_FORMAT_GROUP reads.
///
/// There's no way to ask the kernel how many members a group has. And if we
/// pass a group read a buffer that's too small, the kernel won't just
/// return a truncated result; it returns ENOSPC and leaves the buffer
/// untouched. So the buffer just has to be large enough.
///
/// Since we're borrowed while building group members, adding members can
/// increment this counter. But it's harder to decrement it when a member
/// gets dropped: we don't require that a Group outlive its members, so they
/// can't necessarily update their `Group`'s count from a `Drop` impl. So we
/// just increment, giving us an overestimate, and then correct the count
/// when we actually do a read.
///
/// This includes the dummy counter for the group itself.
max_members: usize,
}
/// A collection of counts from a [`Group`] of counters.
///
/// This is the type returned by calling [`read`] on a [`Group`].
/// You can index it with a reference to a specific `Counter`:
///
/// # fn main() -> std::io::Result<()> {
/// # use perf_event::{Builder, Group};
/// # let mut group = Group::new()?;
/// # let cycles = Builder::new().group(&mut group).build()?;
/// # let insns = Builder::new().group(&mut group).build()?;
/// let counts = group.read()?;
/// println!("cycles / instructions: {} / {} ({:.2} cpi)",
/// counts[&cycles],
/// counts[&insns],
/// (counts[&cycles] as f64 / counts[&insns] as f64));
/// # Ok(()) }
///
/// Or you can iterate over the results it contains:
///
/// # fn main() -> std::io::Result<()> {
/// # use perf_event::Group;
/// # let counts = Group::new()?.read()?;
/// for (id, value) in &counts {
/// println!("Counter id {} has value {}", id, value);
/// }
/// # Ok(()) }
///
/// The `id` values produced by this iteration are internal identifiers assigned
/// by the kernel. You can use the [`Counter::id`] method to find a
/// specific counter's id.
///
/// For some kinds of events, the kernel may use timesharing to give all
/// counters access to scarce hardware registers. You can see how long a group
/// was actually running versus the entire time it was enabled using the
/// `time_enabled` and `time_running` methods:
///
/// # fn main() -> std::io::Result<()> {
/// # use perf_event::{Builder, Group};
/// # let mut group = Group::new()?;
/// # let insns = Builder::new().group(&mut group).build()?;
/// # let counts = group.read()?;
/// let scale = counts.time_enabled() as f64 /
/// counts.time_running() as f64;
/// for (id, value) in &counts {
/// print!("Counter id {} has value {}",
/// id, (*value as f64 * scale) as u64);
/// if scale > 1.0 {
/// print!(" (estimated)");
/// }
/// println!();
/// }
///
/// # Ok(()) }
///
/// [`read`]: Group::read
pub struct Counts {
// Raw results from the `read`.
data: Vec<u64>,
}
/// The value of a counter, along with timesharing data.
///
/// Some counters are implemented in hardware, and the processor can run
/// only a fixed number of them at a time. If more counters are requested
/// than the hardware can support, the kernel timeshares them on the
/// hardware.
///
/// This struct holds the value of a counter, together with the time it was
/// enabled, and the proportion of that for which it was actually running.
#[repr(C)]
pub struct CountAndTime {
/// The counter value.
///
/// The meaning of this field depends on how the counter was configured when
/// it was built; see ['Builder'].
pub count: u64,
/// How long this counter was enabled by the program, in nanoseconds.
pub time_enabled: u64,
/// How long the kernel actually ran this counter, in nanoseconds.
///
/// If `time_enabled == time_running`, then the counter ran for the entire
/// period it was enabled, without interruption. Otherwise, the counter
/// shared the underlying hardware with others, and you should prorate its
/// value accordingly.
pub time_running: u64,
}
impl<'a> EventPid<'a> {
// Return the `pid` arg and the `flags` bits representing `self`.
fn as_args(&self) -> (pid_t, u32) {
match self {
EventPid::ThisProcess => (0, 0),
EventPid::Other(pid) => (*pid, 0),
EventPid::CGroup(file) => (file.as_raw_fd(), sys::bindings::PERF_FLAG_PID_CGROUP),
}
}
}
impl<'a> Default for Builder<'a> {
fn default() -> Builder<'a> {
let mut attrs = perf_event_attr {
// Setting `size` accurately will not prevent the code from working
// on older kernels. The module comments for `perf_event_open_sys`
// explain why in far too much detail.
size: std::mem::size_of::<perf_event_attr>() as u32,
..perf_event_attr::default()
};
attrs.set_disabled(1);
attrs.set_exclude_kernel(1); // don't count time in kernel
attrs.set_exclude_hv(1); // don't count time in hypervisor
// Request data for `time_enabled` and `time_running`.
attrs.read_format |= sys::bindings::PERF_FORMAT_TOTAL_TIME_ENABLED as u64
| sys::bindings::PERF_FORMAT_TOTAL_TIME_RUNNING as u64;
let kind = Event::Hardware(events::Hardware::INSTRUCTIONS);
attrs.type_ = kind.r#type();
attrs.config = kind.config();
Builder {
attrs,
who: EventPid::ThisProcess,
cpu: None,
group: None,
}
}
}
impl<'a> Builder<'a> {
/// Return a new `Builder`, with all parameters set to their defaults.
pub fn new() -> Builder<'a> {
Builder::default()
}
/// Observe the calling process. (This is the default.)
pub fn observe_self(mut self) -> Builder<'a> {
self.who = EventPid::ThisProcess;
self
}
/// Observe the process with the given process id. This requires
/// [`CAP_SYS_PTRACE`][man-capabilities] capabilities.
///
/// [man-capabilities]: http://man7.org/linux/man-pages/man7/capabilities.7.html
pub fn observe_pid(mut self, pid: pid_t) -> Builder<'a> {
self.who = EventPid::Other(pid);
self
}
/// Observe code running in the given [cgroup][man-cgroups] (container). The
/// `cgroup` argument should be a `File` referring to the cgroup's directory
/// in the cgroupfs filesystem.
///
/// [man-cgroups]: http://man7.org/linux/man-pages/man7/cgroups.7.html
pub fn observe_cgroup(mut self, cgroup: &'a File) -> Builder<'a> {
self.who = EventPid::CGroup(cgroup);
self
}
/// Observe only code running on the given CPU core.
pub fn one_cpu(mut self, cpu: usize) -> Builder<'a> {
self.cpu = Some(cpu);
self
}
/// Observe code running on any CPU core. (This is the default.)
pub fn any_cpu(mut self) -> Builder<'a> {
self.cpu = None;
self
}
/// Set whether this counter is inherited by new threads.
///
/// When this flag is set, this counter observes activity in new threads
/// created by any thread already being observed.
///
/// By default, the flag is unset: counters are not inherited, and observe
/// only the threads specified when they are created.
///
/// This flag cannot be set if the counter belongs to a `Group`. Doing so
/// will result in an error when the counter is built. This is a kernel
/// limitation.
pub fn inherit(mut self, inherit: bool) -> Builder<'a> {
let flag = if inherit { 1 } else { 0 };
self.attrs.set_inherit(flag);
self
}
/// Count events of the given kind. This accepts an [`Event`] value,
/// or any type that can be converted to one, so you can pass [`Hardware`],
/// [`Software`] and [`Cache`] values directly.
///
/// The default is to count retired instructions, or
/// `Hardware::INSTRUCTIONS` events.
///
/// For example, to count level 1 data cache references and misses, pass the
/// appropriate `events::Cache` values:
///
/// # fn main() -> std::io::Result<()> {
/// use perf_event::{Builder, Group};
/// use perf_event::events::{Cache, CacheOp, CacheResult, WhichCache};
///
/// const ACCESS: Cache = Cache {
/// which: WhichCache::L1D,
/// operation: CacheOp::READ,
/// result: CacheResult::ACCESS,
/// };
/// const MISS: Cache = Cache { result: CacheResult::MISS, ..ACCESS };
///
/// let mut group = Group::new()?;
/// let access_counter = Builder::new().group(&mut group).kind(ACCESS).build()?;
/// let miss_counter = Builder::new().group(&mut group).kind(MISS).build()?;
/// # Ok(()) }
///
/// [`Hardware`]: events::Hardware
/// [`Software`]: events::Software
/// [`Cache`]: events::Cache
pub fn kind<K: Into<Event>>(mut self, kind: K) -> Builder<'a> {
let kind = kind.into();
self.attrs.type_ = kind.r#type();
self.attrs.config = kind.config();
self
}
/// Place the counter in the given [`Group`]. Groups allow a set of counters
/// to be enabled, disabled, or read as a single atomic operation, so that
/// the counts can be usefully compared.
///
/// [`Group`]: struct.Group.html
pub fn group(mut self, group: &'a mut Group) -> Builder<'a> {
self.group = Some(group);
// man page: "Members of a group are usually initialized with disabled
// set to zero."
self.attrs.set_disabled(0);
self
}
/// Construct a [`Counter`] according to the specifications made on this
/// `Builder`.
///
/// A freshly built `Counter` is disabled. To begin counting events, you
/// must call [`enable`] on the `Counter` or the `Group` to which it belongs.
///
/// If the `Builder` requests features that the running kernel does not
/// support, it returns `Err(e)` where `e.kind() == ErrorKind::Other` and
/// `e.raw_os_error() == Some(libc::E2BIG)`.
///
/// Unfortunately, problems in counter configuration are detected at this
/// point, by the kernel, not earlier when the offending request is made on
/// the `Builder`. The kernel's returned errors are not always helpful.
///
/// [`Counter`]: struct.Counter.html
/// [`enable`]: struct.Counter.html#method.enable
pub fn build(mut self) -> std::io::Result<Counter> {
let cpu = match self.cpu {
Some(cpu) => cpu as c_int,
None => -1,
};
let (pid, flags) = self.who.as_args();
let group_fd = match self.group {
Some(ref mut g) => {
g.max_members += 1;
g.file.as_raw_fd() as c_int
}
None => -1,
};
let file = unsafe {
File::from_raw_fd(check_errno_syscall(|| {
sys::perf_event_open(&mut self.attrs, pid, cpu, group_fd, flags as c_ulong)
})?)
};
// If we're going to be part of a Group, retrieve the ID the kernel
// assigned us, so we can find our results in a Counts structure. Even
// if we're not part of a group, we'll use it in `Debug` output.
let mut id = 0_u64;
check_errno_syscall(|| unsafe { sys::ioctls::ID(file.as_raw_fd(), &mut id) })?;
Ok(Counter { file, id })
}
}
impl Counter {
/// Return this counter's kernel-assigned unique id.
///
/// This can be useful when iterating over [`Counts`].
///
/// [`Counts`]: struct.Counts.html
pub fn id(&self) -> u64 {
self.id
}
/// 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 `Counter`s as a single atomic operation.
///
/// [`reset`]: #method.reset
/// [`enable`]: struct.Group.html#method.enable
pub fn enable(&mut self) -> io::Result<()> {
check_errno_syscall(|| unsafe { sys::ioctls::ENABLE(self.file.as_raw_fd(), 0) }).map(|_| ())
}
/// 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 `Counter`s as a single atomic operation.
///
/// [`disable`]: struct.Group.html#method.disable
pub fn disable(&mut self) -> io::Result<()> {
check_errno_syscall(|| unsafe { sys::ioctls::DISABLE(self.file.as_raw_fd(), 0) })
.map(|_| ())
}
/// Reset the value of this `Counter` to zero.
///
/// Note that `Group` also has a [`reset`] method, which resets all
/// its member `Counter`s as a single atomic operation.
///
/// [`reset`]: struct.Group.html#method.reset
pub fn reset(&mut self) -> io::Result<()> {
check_errno_syscall(|| unsafe { sys::ioctls::RESET(self.file.as_raw_fd(), 0) }).map(|_| ())
}
/// Return this `Counter`'s current value as a `u64`.
///
/// Consider using the [`read_count_and_time`] method instead of this one. Some
/// counters are implemented in hardware, and the processor can support only
/// a certain number running at a time. If more counters are requested than
/// the hardware can support, the kernel timeshares them on the hardware.
/// This method gives you no indication whether this has happened;
/// `read_count_and_time` does.
///
/// Note that `Group` also has a [`read`] method, which reads all
/// its member `Counter`s' values at once.
///
/// [`read`]: Group::read
/// [`read_count_and_time`]: Counter::read_count_and_time
pub fn read(&mut self) -> io::Result<u64> {
Ok(self.read_count_and_time()?.count)
}
/// Return this `Counter`'s current value and timesharing data.
///
/// Some counters are implemented in hardware, and the processor can run
/// only a fixed number of them at a time. If more counters are requested
/// than the hardware can support, the kernel timeshares them on the
/// hardware.
///
/// This method returns a [`CountAndTime`] struct, whose `count` field holds
/// the counter's value, and whose `time_enabled` and `time_running` fields
/// indicate how long you had enabled the counter, and how long the counter
/// was actually scheduled on the processor. This lets you detect whether
/// the counter was timeshared, and adjust your use accordingly. Times
/// are reported in nanoseconds.
///
/// # use perf_event::Builder;
/// # fn main() -> std::io::Result<()> {
/// # let mut counter = Builder::new().build()?;
/// let cat = counter.read_count_and_time()?;
/// if cat.time_running == 0 {
/// println!("No data collected.");
/// } else if cat.time_running < cat.time_enabled {
/// // Note: this way of scaling is accurate, but `u128` division
/// // is usually implemented in software, which may be slow.
/// println!("{} instructions (estimated)",
/// (cat.count as u128 *
/// cat.time_enabled as u128 / cat.time_running as u128) as u64);
/// } else {
/// println!("{} instructions", cat.count);
/// }
/// # Ok(()) }
///
/// Note that `Group` also has a [`read`] method, which reads all
/// its member `Counter`s' values at once.
///
/// [`read`]: Group::read
pub fn read_count_and_time(&mut self) -> io::Result<CountAndTime> {
let mut buf = [0_u64; 3];
self.file.read_exact(u64::slice_as_bytes_mut(&mut buf))?;
let cat = CountAndTime {
count: buf[0],
time_enabled: buf[1],
time_running: buf[2],
};
// Does the kernel ever return nonsense?
assert!(cat.time_running <= cat.time_enabled);
Ok(cat)
}
}
impl std::fmt::Debug for Counter {
fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
write!(
fmt,
"Counter {{ fd: {}, id: {} }}",
self.file.as_raw_fd(),
self.id
)
}
}
impl Group {
/// Construct a new, empty `Group`.
#[allow(unused_parens)]
pub fn new() -> io::Result<Group> {
// Open a placeholder perf counter that we can add other events to.
let mut attrs = perf_event_attr {
size: std::mem::size_of::<perf_event_attr>() as u32,
type_: sys::bindings::PERF_TYPE_SOFTWARE,
config: sys::bindings::PERF_COUNT_SW_DUMMY as u64,
..perf_event_attr::default()
};
attrs.set_disabled(1);
attrs.set_exclude_kernel(1);
attrs.set_exclude_hv(1);
// Arrange to be able to identify the counters we read back.
attrs.read_format = (sys::bindings::PERF_FORMAT_TOTAL_TIME_ENABLED
| sys::bindings::PERF_FORMAT_TOTAL_TIME_RUNNING
| sys::bindings::PERF_FORMAT_ID
| sys::bindings::PERF_FORMAT_GROUP) as u64;
let file = unsafe {
File::from_raw_fd(check_errno_syscall(|| {
sys::perf_event_open(&mut attrs, 0, -1, -1, 0)
})?)
};
// Retrieve the ID the kernel assigned us.
let mut id = 0_u64;
check_errno_syscall(|| unsafe { sys::ioctls::ID(file.as_raw_fd(), &mut id) })?;
Ok(Group {
file,
id,
max_members: 1,
})
}
/// Allow all `Counter`s in this `Group` to begin counting their designated
/// events, as a single atomic operation.
///
/// This does not affect whatever values the `Counter`s had previously; new
/// events add to the current counts. To clear the `Counter`s, use the
/// [`reset`] method.
///
/// [`reset`]: #method.reset
pub fn enable(&mut self) -> io::Result<()> {
self.generic_ioctl(sys::ioctls::ENABLE)
}
/// Make all `Counter`s in this `Group` stop counting their designated
/// events, as a single atomic operation. Their counts are unaffected.
pub fn disable(&mut self) -> io::Result<()> {
self.generic_ioctl(sys::ioctls::DISABLE)
}
/// Reset all `Counter`s in this `Group` to zero, as a single atomic operation.
pub fn reset(&mut self) -> io::Result<()> {
self.generic_ioctl(sys::ioctls::RESET)
}
/// Perform some group ioctl.
///
/// `f` must be a syscall that sets `errno` and returns `-1` on failure.
fn generic_ioctl(&mut self, f: unsafe fn(c_int, c_uint) -> c_int) -> io::Result<()> {
check_errno_syscall(|| unsafe {
f(self.file.as_raw_fd(), sys::bindings::PERF_IOC_FLAG_GROUP)
})
.map(|_| ())
}
/// Return the values of all the `Counter`s in this `Group` as a [`Counts`]
/// value.
///
/// A `Counts` value is a map from specific `Counter`s to their values. You
/// can find a specific `Counter`'s value by indexing:
///
/// ```ignore
/// let mut group = Group::new()?;
/// let counter1 = Builder::new().group(&mut group).kind(...).build()?;
/// let counter2 = Builder::new().group(&mut group).kind(...).build()?;
/// ...
/// let counts = group.read()?;
/// println!("Rhombus inclinations per taxi medallion: {} / {} ({:.0}%)",
/// counts[&counter1],
/// counts[&counter2],
/// (counts[&counter1] as f64 / counts[&counter2] as f64) * 100.0);
/// ```
///
/// [`Counts`]: struct.Counts.html
pub fn read(&mut self) -> io::Result<Counts> {
// Since we passed `PERF_FORMAT_{ID,GROUP,TOTAL_TIME_{ENABLED,RUNNING}}`,
// the data we'll read has the form:
//
// struct read_format {
// u64 nr; /* The number of events */
// u64 time_enabled; /* if PERF_FORMAT_TOTAL_TIME_ENABLED */
// u64 time_running; /* if PERF_FORMAT_TOTAL_TIME_RUNNING */
// struct {
// u64 value; /* The value of the event */
// u64 id; /* if PERF_FORMAT_ID */
// } values[nr];
// };
let mut data = vec![0_u64; 3 + 2 * self.max_members];
assert_eq!(
self.file.read(u64::slice_as_bytes_mut(&mut data))?,
std::mem::size_of_val(&data[..])
);
let counts = Counts { data };
// CountsIter assumes that the group's dummy count appears first.
assert_eq!(counts.nth_ref(0).0, self.id);
// Does the kernel ever return nonsense?
assert!(counts.time_running() <= counts.time_enabled());
// Update `max_members` for the next read.
self.max_members = counts.len();
Ok(counts)
}
}
impl std::fmt::Debug for Group {
fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
write!(
fmt,
"Group {{ fd: {}, id: {} }}",
self.file.as_raw_fd(),
self.id
)
}
}
impl Counts {
/// Return the number of counters this `Counts` holds results for.
#[allow(clippy::len_without_is_empty)] // Groups are never empty.
pub fn len(&self) -> usize {
self.data[0] as usize
}
/// Return the number of nanoseconds the `Group` was enabled that
/// contributed to this `Counts`' contents.
pub fn time_enabled(&self) -> u64 {
self.data[1]
}
/// Return the number of nanoseconds the `Group` was actually collecting
/// counts that contributed to this `Counts`' contents.
pub fn time_running(&self) -> u64 {
self.data[2]
}
/// Return a range of indexes covering the count and id of the `n`'th counter.
fn nth_index(n: usize) -> std::ops::Range<usize> {
let base = 3 + 2 * n;
base..base + 2
}
/// Return the id and count of the `n`'th counter. This returns a reference
/// to the count, for use by the `Index` implementation.
fn nth_ref(&self, n: usize) -> (u64, &u64) {
let id_val = &self.data[Counts::nth_index(n)];
// (id, &value)
(id_val[1], &id_val[0])
}
}
/// An iterator over the counter values in a [`Counts`], returned by
/// [`Group::read`].
///
/// Each item is a pair `(id, &value)`, where `id` is the number assigned to the
/// counter by the kernel (see `Counter::id`), and `value` is that counter's
/// value.
///
/// [`Counts`]: struct.Counts.html
/// [`Counter::id`]: struct.Counter.html#method.id
/// [`Group::read`]: struct.Group.html#method.read
pub struct CountsIter<'c> {
counts: &'c Counts,
next: usize,
}
impl<'c> Iterator for CountsIter<'c> {
type Item = (u64, &'c u64);
fn next(&mut self) -> Option<(u64, &'c u64)> {
if self.next >= self.counts.len() {
return None;
}
let result = self.counts.nth_ref(self.next);
self.next += 1;
Some(result)
}
}
impl<'c> IntoIterator for &'c Counts {
type Item = (u64, &'c u64);
type IntoIter = CountsIter<'c>;
fn into_iter(self) -> CountsIter<'c> {
CountsIter {
counts: self,
next: 1, // skip the `Group` itself, it's just a dummy.
}
}
}
impl Counts {
/// Return the value recorded for `member` in `self`, or `None` if `member`
/// is not present.
///
/// If you know that `member` is in the group, you can simply index:
///
/// # fn main() -> std::io::Result<()> {
/// # use perf_event::{Builder, Group};
/// # let mut group = Group::new()?;
/// # let cycle_counter = Builder::new().group(&mut group).build()?;
/// # let counts = group.read()?;
/// let cycles = counts[&cycle_counter];
/// # Ok(()) }
pub fn get(&self, member: &Counter) -> Option<&u64> {
self.into_iter()
.find(|&(id, _)| id == member.id)
.map(|(_, value)| value)
}
/// Return an iterator over the counts in `self`.
///
/// # fn main() -> std::io::Result<()> {
/// # use perf_event::Group;
/// # let counts = Group::new()?.read()?;
/// for (id, value) in &counts {
/// println!("Counter id {} has value {}", id, value);
/// }
/// # Ok(()) }
///
/// Each item is a pair `(id, &value)`, where `id` is the number assigned to
/// the counter by the kernel (see `Counter::id`), and `value` is that
/// counter's value.
pub fn iter(&self) -> CountsIter {
<&Counts as IntoIterator>::into_iter(self)
}
}
impl std::ops::Index<&Counter> for Counts {
type Output = u64;
fn index(&self, index: &Counter) -> &u64 {
self.get(index).unwrap()
}
}
impl std::fmt::Debug for Counts {
fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
fmt.debug_map().entries(self.into_iter()).finish()
}
}
/// A type whose values can be safely accessed as a slice of bytes.
///
/// # Safety
///
/// `Self` must be a type such that storing a value in memory
/// initializes all the bytes of that memory, so that
/// `slice_as_bytes_mut` can never expose uninitialized bytes to the
/// caller.
unsafe trait SliceAsBytesMut: Sized {
fn slice_as_bytes_mut(slice: &mut [Self]) -> &mut [u8] {
unsafe {
std::slice::from_raw_parts_mut(
slice.as_mut_ptr() as *mut u8,
std::mem::size_of_val(slice),
)
}
}
}
unsafe impl SliceAsBytesMut for u64 {}
/// Produce an `io::Result` from an errno-style system call.
///
/// An 'errno-style' system call is one that reports failure by returning -1 and
/// setting the C `errno` value when an error occurs.
fn check_errno_syscall<F, R>(f: F) -> io::Result<R>
where
F: FnOnce() -> R,
R: PartialOrd + Default,
{
let result = f();
if result < R::default() {
Err(io::Error::last_os_error())
} else {
Ok(result)
}
}
#[test]
fn simple_build() {
Builder::new()
.build()
.expect("Couldn't build default Counter");
}
#[test]
#[cfg(target_os = "linux")]
fn test_error_code_is_correct() {
// This configuration should always result in EINVAL
let builder = Builder::new()
// CPU_CLOCK is literally always supported so we don't have to worry
// about test failures when in VMs.
.kind(events::Software::CPU_CLOCK)
// There should _hopefully_ never be a system with this many CPUs.
.one_cpu(i32::MAX as usize);
match builder.build() {
Ok(_) => panic!("counter construction was not supposed to succeed"),
Err(e) => assert_eq!(e.raw_os_error(), Some(libc::EINVAL)),
}
}