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/*
* Copyright (C) 2015 Tim Mayberry <mojofunk@gmail.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifndef ARDOUR_DSP_LOAD_CALCULATOR_H
#define ARDOUR_DSP_LOAD_CALCULATOR_H
#include <stdint.h>
#include <cassert>
#include <algorithm>
namespace ARDOUR {
class DSPLoadCalculator {
public:
DSPLoadCalculator()
: m_max_time_us(0)
, m_start_timestamp_us(0)
, m_stop_timestamp_us(0)
, m_dsp_load(0)
{
}
void set_max_time(double samplerate, uint32_t period_size) {
m_max_time_us = period_size * 1e6 / samplerate;
}
void set_max_time_us(uint64_t max_time_us) {
assert(max_time_us != 0);
m_max_time_us = max_time_us;
}
int64_t get_max_time_us() const { return m_max_time_us; }
void set_start_timestamp_us(int64_t start_timestamp_us)
{
m_start_timestamp_us = start_timestamp_us;
}
void set_stop_timestamp_us(int64_t stop_timestamp_us)
{
m_stop_timestamp_us = stop_timestamp_us;
/* querying the performance counter can fail occasionally (-1).
* Also on some multi-core systems, timers are CPU specific and not
* synchronized. We assume they differ more than a few milliseconds
* (4 * nominal cycle time) and simply ignore cases where the
* execution switches cores.
*/
if (m_start_timestamp_us < 0 || m_stop_timestamp_us < 0 ||
m_start_timestamp_us > m_stop_timestamp_us ||
elapsed_time_us() > max_timer_error_us()) {
return;
}
const float load = (float) elapsed_time_us() / (float)m_max_time_us;
if (load > m_dsp_load || load > 1.0) {
m_dsp_load = load;
} else {
const float alpha = 0.2f * (m_max_time_us * 1e-6f);
m_dsp_load = std::min (1.f, m_dsp_load);
m_dsp_load += alpha * (load - m_dsp_load) + 1e-12;
}
}
int64_t elapsed_time_us()
{
return m_stop_timestamp_us - m_start_timestamp_us;
}
/**
* @return a decimal value between 0.0 and 1.0 representing the percentage
* of time spent between start and stop in proportion to the max expected time
* in microseconds(us).
*/
float get_dsp_load() const
{
assert (m_dsp_load >= 0.f); // since stop > start is assured this cannot happen.
return std::min (1.f, m_dsp_load);
}
/**
* @return an unbound value representing the percentage of time spent between
* start and stop in proportion to the max expected time in microseconds(us).
* This is useful for cases to estimate overload (e.g. Dummy backend)
*/
float get_dsp_load_unbound() const
{
assert (m_dsp_load >= 0.f);
return m_dsp_load;
}
/**
* The maximum error in timestamp values that will be tolerated before the
* current dsp load sample will be ignored
*/
int64_t max_timer_error_us() { return 4 * m_max_time_us; }
private: // data
int64_t m_max_time_us;
int64_t m_start_timestamp_us;
int64_t m_stop_timestamp_us;
float m_dsp_load;
};
} // namespace ARDOUR
#endif // ARDOUR_DSP_LOAD_CALCULATOR_H
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