/**
* collectd - src/utils_latency.c
- * Copyright (C) 2013 Florian Forster
+ * Copyright (C) 2013 Florian Forster
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
**/
#include "collectd.h"
+
#include "plugin.h"
#include "utils_latency.h"
#include "common.h"
if (lc->num > 0) // if the histogram has data then iterate else skip
{
double width_change_ratio = ((double) old_bin_width) / ((double) new_bin_width);
- size_t i;
- for (i = 0; i < HISTOGRAM_NUM_BINS; i++)
+ for (size_t i = 0; i < HISTOGRAM_NUM_BINS; i++)
{
size_t new_bin = (size_t) (((double) i) * width_change_ratio);
if (i == new_bin)
CDTIME_T_TO_DOUBLE (new_bin_width));
} /* }}} void change_bin_width */
-latency_counter_t *latency_counter_create () /* {{{ */
+latency_counter_t *latency_counter_create (void) /* {{{ */
{
latency_counter_t *lc;
- lc = malloc (sizeof (*lc));
+ lc = calloc (1, sizeof (*lc));
if (lc == NULL)
return (NULL);
- memset (lc, 0, sizeof (*lc));
- latency_counter_reset (lc);
lc->bin_width = HISTOGRAM_DEFAULT_BIN_WIDTH;
+ latency_counter_reset (lc);
return (lc);
} /* }}} latency_counter_t *latency_counter_create */
return;
cdtime_t bin_width = lc->bin_width;
+ cdtime_t max_bin = (lc->max - 1) / lc->bin_width;
+
+/*
+ If max latency is REDUCE_THRESHOLD times less than histogram's range,
+ then cut it in half. REDUCE_THRESHOLD must be >= 2.
+ Value of 4 is selected to reduce frequent changes of bin width.
+*/
+#define REDUCE_THRESHOLD 4
+ if ((lc->num > 0) && (lc->bin_width >= HISTOGRAM_DEFAULT_BIN_WIDTH * 2)
+ && (max_bin < HISTOGRAM_NUM_BINS / REDUCE_THRESHOLD))
+ {
+ /* new bin width will be the previous power of 2 */
+ bin_width = bin_width / 2;
+
+ DEBUG("utils_latency: latency_counter_reset: max_latency = %.3f; "
+ "max_bin = %"PRIu64"; old_bin_width = %.3f; new_bin_width = %.3f;",
+ CDTIME_T_TO_DOUBLE (lc->max),
+ max_bin,
+ CDTIME_T_TO_DOUBLE (lc->bin_width),
+ CDTIME_T_TO_DOUBLE (bin_width));
+ }
+
memset (lc, 0, sizeof (*lc));
/* preserve bin width */