tsc-time 0.1.0

Time stamp counter (TSC) based timer

Time-stamp counter (TSC) timer

This library provides a time-stamp counter (TSC) based timer for micro benchmarking.


# #![feature(test)]
# extern crate test;
# use self::test::black_box;
# use tsc::*;
// The function we want to time:
pub fn fibonacci(n: u64) -> u64 {
    match n {
        0 | 1 => 1,
        n => fibonacci(n - 1) + fibonacci(n - 2),

// Non-invariant TSCs might produce unreliable results:
assert!(has_invariant_tsc(), "The TSC is not invariant!");

let (duration, result) =
    Duration::span(|| black_box(fibonacci(black_box(8))));

assert_eq!(result, 34);

println!("Reference cycle count: {} cycles.", duration.cycles());
// On my machine prints: "Reference cycle count: 951 cycles."


  • The TSC runs at a different frequency than the CPU clock frequency, so the cycles reported here are "reference cycles" and not real CPU clock cycles.

  • If the TSC is not invariant (Nehalem-and-later) the measurements might not be very accurate due to turbo boost, speed-step, power management, etc.

  • Converting "reference cycles" to time (e.g., nanoseconds) is, in general, not possible to do reliably in user-space.

  • One might want to disable preemption and hard interrupts before timing (see How to Benchmark Code Execution Times on IntelĀ® IA-32 and IA-64 Instruction Set Architectures) to further improve the accuracy of the measurements.