fastmm::TscCalibrator Class Reference

Long-baseline TSC calibration for the calibrator (control) thread. More...

#include <fastmm/core/time.hpp>

Public Member Functions
	TscCalibrator (ClockReadings readings=system_clock_readings()) noexcept
TscCalibration	start (Duration window=milliseconds(50)) noexcept
TscRecalibration	update () noexcept
const TscCalibration &	current () const noexcept

Static Public Attributes
static constexpr Duration	kMinBaseline = milliseconds(500)

Detailed Description

Long-baseline TSC calibration for the calibrator (control) thread.

start() measures an initial rate over a short spin. update() takes only a fresh anchor and derives the rate from the whole interval since the previous anchor, against CLOCK_MONOTONIC_RAW:

• anchor jitter (clock_gettime latency spikes of tens of microseconds on a busy or virtualised host) costs a few ppm over a 10 s baseline instead of thousands of ppm over a 50 ms window, which used to drift the mapping by milliseconds between recalibrations and force steps;
• NTP slews and host wall-clock steps (WSL2 resynchronising with Windows) cannot distort the rate. A wall-clock step is reported separately in host_step_ns; the published anchor still follows CLOCK_REALTIME, so TscClock steps with the host when it has to.

Constructor & Destructor Documentation

TscCalibrator()

fastmm::TscCalibrator::TscCalibrator ( ClockReadings  readings = system_clock_readings() )

inlineexplicitnoexcept

Member Function Documentation

start()

TscCalibration fastmm::TscCalibrator::start ( Duration  window = milliseconds(50) )

noexcept

update()

TscRecalibration fastmm::TscCalibrator::update ( )

noexcept

current()

const TscCalibration & fastmm::TscCalibrator::current ( ) const

inlinenoexcept

Member Data Documentation

kMinBaseline

constexpr Duration fastmm::TscCalibrator::kMinBaseline = milliseconds(500)

staticconstexpr