Crate kala 

kala provides a simple API for timing sections of code with sub-nanosecond precision. It can run and time a function while preventing interference from CPU and compiler instruction reordering. It uses CPU hardware clock counters like the Time Stamp Counter (TSC) on x86-64 or the Cycle Counter Register (CCNT) on AArch64 (with an std::time::Instant fallback on other architectures).

Example

use kala::Stopwatch;

let sw = Stopwatch::new(); // Most efficient to create once and re-use.
let nanos: f64 = sw.time(|| 2 + 3).to_nanos(); // Runs closure _once_.
println!("Function took {nanos:.2} nanos");

Note on Precision

While kala goes to extreme lengths to provide the highest level of timing precision, ultimately measurement precision depends on your CPU. Some CPUs—especially those using the AArch64 architecture—have very coarse CPU time counters. For instance, the Apple M1 and M2 (but not M3 and later) use a CPU time counter with a 24 MHz frequency. Thus the clock “ticks” every ~41.67 nanoseconds. No other clock source on that CPU can offer better granularity.

It’s still possible to extract finer timing precision from such data, but that requires collecting many measurements with an excellent experiment design and great statistics. This is the job of benchmarking harnesses that use kala, not kala itself.

See the API docs for kala::Duration for advice on avoiding conversion losses and getting the highest precision.

Structs

Duration

Represents a span of time.

Stopwatch

Allows precisely timing function executions.

Enums

StorageType

Describes the possible internal storage types for a Duration.