load.c File Reference

functions related to load calculations More...

#include "platform.h"
#include "gnunet_util_lib.h"

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Data Structures
struct	GNUNET_LOAD_Value
	Values we track for load calculations. More...

Macros
#define	LOG(kind, ...)   GNUNET_log_from (kind, "util-load", __VA_ARGS__)

Functions
static void	internal_update (struct GNUNET_LOAD_Value *load)
struct GNUNET_LOAD_Value *	GNUNET_LOAD_value_init (struct GNUNET_TIME_Relative autodecline)
	Create a new load value. More...
void	GNUNET_LOAD_value_set_decline (struct GNUNET_LOAD_Value *load, struct GNUNET_TIME_Relative autodecline)
	Change the value by which the load automatically declines. More...
static void	calculate_load (struct GNUNET_LOAD_Value *load)
	Recalculate our load value. More...
double	GNUNET_LOAD_get_load (struct GNUNET_LOAD_Value *load)
	Get the current load. More...
double	GNUNET_LOAD_get_average (struct GNUNET_LOAD_Value *load)
	Get the average value given to update so far. More...
void	GNUNET_LOAD_update (struct GNUNET_LOAD_Value *load, uint64_t data)
	Update the current load. More...

Detailed Description

functions related to load calculations

Author

Christian Grothoff

Definition in file load.c.

Macro Definition Documentation

LOG

#define LOG	(		kind,
			...
	)		GNUNET_log_from (kind, "util-load", __VA_ARGS__)

Definition at line 31 of file load.c.

Function Documentation

internal_update()

static void internal_update ( struct GNUNET_LOAD_Value *  load )

static

Definition at line 84 of file load.c.

{
  struct GNUNET_TIME_Relative delta;
  unsigned int n;
 
  if (load->autodecline.rel_value_us ==
      GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us)
    return;
  delta = GNUNET_TIME_absolute_get_duration (load->last_update);
  if (delta.rel_value_us < load->autodecline.rel_value_us)
    return;
  if (0 == load->autodecline.rel_value_us)
  {
    load->runavg_delay = 0.0;
    load->load = 0;
    return;
  }
  n = delta.rel_value_us / load->autodecline.rel_value_us;
  if (n > 16)
  {
    load->runavg_delay = 0.0;
    load->load = 0;
    return;
  }
  while (n > 0)
  {
    n--;
    load->runavg_delay = (load->runavg_delay * 7.0) / 8.0;
  }
}

References delta, GNUNET_TIME_absolute_get_duration(), GNUNET_TIME_UNIT_FOREVER_REL, load(), and GNUNET_TIME_Relative::rel_value_us.

Referenced by GNUNET_LOAD_get_average(), GNUNET_LOAD_get_load(), and GNUNET_LOAD_value_set_decline().

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calculate_load()

static void calculate_load ( struct GNUNET_LOAD_Value *  load )

static

Recalculate our load value.

Parameters

load	load to update

Definition at line 157 of file load.c.

{
  double stddev;
  double avgdel;
  double sum_val_i;
  double n;
  double nm1;
 
  if (load->cummulative_request_count <= 1)
    return;
  /* calculate std dev of latency; we have for n values of "i" that:
   *
   * avg = (sum val_i) / n
   * stddev = (sum (val_i - avg)^2) / (n-1)
   * = (sum (val_i^2 - 2 avg val_i + avg^2) / (n-1)
   * = (sum (val_i^2) - 2 avg sum (val_i) + n * avg^2) / (n-1)
   */sum_val_i = (double) load->cummulative_delay;
  n = ((double) load->cummulative_request_count);
  nm1 = n - 1.0;
  avgdel = sum_val_i / n;
  stddev =
    (((double) load->cummulative_squared_delay) - 2.0 * avgdel * sum_val_i
     + n * avgdel * avgdel) / nm1;
  if (stddev <= 0)
    stddev = 0.01;              /* must have been rounding error or zero; prevent division by zero */
  /* now calculate load based on how far out we are from
   * std dev; or if we are below average, simply assume load zero */
  if (load->runavg_delay < avgdel)
    load->load = 0.0;
  else
    load->load = (load->runavg_delay - avgdel) / stddev;
}

References load().

Referenced by GNUNET_LOAD_get_load().

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