dsp_load_calculator.h

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/*
 * Copyright (C) 2015-2019 Robin Gareus <robin@gareus.org>
 * 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.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
#ifndef ARDOUR_DSP_LOAD_CALCULATOR_H
#define ARDOUR_DSP_LOAD_CALCULATOR_H
 
#include <glib.h>
#include <stdlib.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_alpha(0)
            , m_dsp_load(0)
        {
                m_calc_avg_load = NULL != g_getenv("ARDOUR_AVG_DSP_LOAD");
        }
 
        void reset () {
                m_dsp_load = 0;
                m_start_timestamp_us = 0;
                m_stop_timestamp_us = 0;
        }
 
        void set_max_time(double samplerate, uint32_t period_size) {
                m_max_time_us = period_size * 1e6 / samplerate;
                m_alpha = 0.2f * (m_max_time_us * 1e-6f);
        }
 
        void set_max_time_us(uint64_t max_time_us) {
                assert(max_time_us != 0);
                m_max_time_us = max_time_us;
                m_alpha = 0.2f * (m_max_time_us * 1e-6f);
        }
 
        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;
                }
                assert (m_max_time_us > 0);
 
                const float load = (float) elapsed_time_us() / (float)m_max_time_us;
                if ((m_calc_avg_load && load > .95f) || (!m_calc_avg_load && (load > m_dsp_load || load > 1.f))) {
                        m_dsp_load = load;
                } else {
                        m_dsp_load = std::min (1.f, m_dsp_load);
                        m_dsp_load += m_alpha * (load - m_dsp_load) + 1e-12;
                }
        }
 
        int64_t elapsed_time_us()
        {
                return m_stop_timestamp_us - m_start_timestamp_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);
        }
 
        float get_dsp_load_unbound() const
        {
                assert (m_dsp_load >= 0.f);
                return m_dsp_load;
        }
 
        int64_t max_timer_error_us() { return 4 * m_max_time_us; }
 
private: // data
        bool    m_calc_avg_load;
        int64_t m_max_time_us;
        int64_t m_start_timestamp_us;
        int64_t m_stop_timestamp_us;
        float m_alpha;
        float m_dsp_load;
};
 
} // namespace ARDOUR
 
#endif // ARDOUR_DSP_LOAD_CALCULATOR_H