ardupilot/libraries/AP_Scheduler/PerfInfo.cpp

#include "PerfInfo.h"

#include <DataFlash/DataFlash.h>
#include <GCS_MAVLink/GCS.h>

extern const AP_HAL::HAL& hal;

//
//  high level performance monitoring
//
//  we measure the main loop time
//

// reset - reset all records of loop time to zero
void AP::PerfInfo::reset()
{
    loop_count = 0;
    max_time = 0;
    min_time = 0;
    long_running = 0;
    sigma_time = 0;
    sigmasquared_time = 0;
}

// ignore_loop - ignore this loop from performance measurements (used to reduce false positive when arming)
void AP::PerfInfo::ignore_this_loop()
{
    ignore_loop = true;
}

// check_loop_time - check latest loop time vs min, max and overtime threshold
void AP::PerfInfo::check_loop_time(uint32_t time_in_micros)
{
    loop_count++;

    // exit if this loop should be ignored
    if (ignore_loop) {
        ignore_loop = false;
        return;
    }

    if( time_in_micros > max_time) {
        max_time = time_in_micros;
    }
    if( min_time == 0 || time_in_micros < min_time) {
        min_time = time_in_micros;
    }
    if (time_in_micros > overtime_threshold_micros) {
        long_running++;
    }
    sigma_time += time_in_micros;
    sigmasquared_time += time_in_micros * time_in_micros;

    /* we keep a filtered loop time for use as G_Dt which is the
       predicted time for the next loop. We remove really excessive
       times from this calculation so as not to throw it off too far
       in case we get a single long loop

       Note that the time we use here is the time between calls to
       check_loop_time() not the time from loop start to loop
       end. This is because we are using the time for time between
       calls to controllers, which has nothing to do with cpu speed.
    */
    const uint32_t now = AP_HAL::micros();
    const uint32_t loop_time_us = now - last_check_us;
    last_check_us = now;
    if (loop_time_us < overtime_threshold_micros + 10000UL) {
        filtered_loop_time = 0.99f * filtered_loop_time + 0.01f * loop_time_us * 1.0e-6f;
    }
}

// get_num_loops: return number of loops used for recording performance
uint16_t AP::PerfInfo::get_num_loops() const
{
    return loop_count;
}

// get_max_time - return maximum loop time (in microseconds)
uint32_t AP::PerfInfo::get_max_time() const
{
    return max_time;
}

// get_min_time - return minumum loop time (in microseconds)
uint32_t AP::PerfInfo::get_min_time() const
{
    return min_time;
}

// get_num_long_running - get number of long running loops
uint16_t AP::PerfInfo::get_num_long_running() const
{
    return long_running;
}

// get_avg_time - return average loop time (in microseconds)
uint32_t AP::PerfInfo::get_avg_time() const
{
    return (sigma_time / loop_count);
}

// get_stddev_time - return stddev of average loop time (in us)
uint32_t AP::PerfInfo::get_stddev_time() const
{
    return sqrtf((sigmasquared_time - (sigma_time*sigma_time)/loop_count) / loop_count);
}

// get_filtered_time - return low pass filtered loop time in seconds
float AP::PerfInfo::get_filtered_time() const
{
    return filtered_loop_time;
}

void AP::PerfInfo::update_logging()
{
    gcs().send_text(MAV_SEVERITY_WARNING,
                    "PERF: %u/%u max=%lu min=%lu F=%u sd=%lu",
                    (unsigned)get_num_long_running(),
                    (unsigned)get_num_loops(),
                    (unsigned long)get_max_time(),
                    (unsigned long)get_min_time(),
                    (unsigned)(get_filtered_time()*1.0e6),
                    (unsigned long)get_stddev_time());
}

void AP::PerfInfo::set_loop_rate(uint16_t rate_hz)
{
    // allow a 20% overrun before we consider a loop "slow":
    overtime_threshold_micros = 1000000/rate_hz * 1.2f;

    if (loop_rate_hz != rate_hz) {
        loop_rate_hz = rate_hz;
        filtered_loop_time = 1.0f / rate_hz;
    }
}