multiload/src/autoscaler.c


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#include <time.h>
#include <glib.h>

#include "autoscaler.h"

/* i wish i could have used C99 initializers instead of writing this function */
void autoscaler_init(AutoScaler *that, unsigned interval, unsigned floor)
{
    that->update_interval = interval;
    that->floor = floor;
    that->max = 0;
    that->count = 0;
    that->last_update = 0;
    that->sum =  0.0f;
    that->last_average = 0.0f;
}


unsigned autoscaler_get_max(AutoScaler *that, unsigned current)
{
    time_t now;

    that->sum += current;
    that->count++;
    time(&now);

    if((float)difftime(now, that->last_update) > that->update_interval)
    {
        float new_average = that->sum / that->count;
        float average;

        if(new_average < that->last_average)
            average = ((that->last_average * 0.5f) + new_average) / 1.5f;
        else
            average = new_average;

        that->max = average * 1.2f;

        that->sum = 0.0f;
        that->count = 0;
        that->last_update = now;
        that->last_average = average;
    }

    that->max = MAX(that->max, current);
    that->max = MAX(that->max, that->floor);
#if 0
    printf("%p max = %u, current = %u, last_average = %f\n", that, that->max, current, that->last_average);
#endif
    return that->max;
}