X-Git-Url: https://git.octo.it/?p=collectd.git;a=blobdiff_plain;f=src%2Futils_latency.c;h=1d3bf2e97c5a749e5ff4fb1b4fef91ecb115f1dc;hp=30f13c70d1d869cc056c70879801e1fab25bc018;hb=a9e50e9e30ecde17e167e271060c8183bfcbf407;hpb=e7aa9832d25a98f78bb5af45a90ec404359537df

diff --git a/src/utils_latency.c b/src/utils_latency.c
index 30f13c70..1d3bf2e9 100644
--- a/src/utils_latency.c
+++ b/src/utils_latency.c
@@ -26,28 +26,23 @@
 
 #include "collectd.h"
 
+#include "common.h"
 #include "plugin.h"
 #include "utils_latency.h"
-#include "common.h"
 
-#include <math.h>
 #include <limits.h>
+#include <math.h>
 
 #ifndef LLONG_MAX
-# define LLONG_MAX 9223372036854775807LL
-#endif
-
-#ifndef HISTOGRAM_NUM_BINS
-# define HISTOGRAM_NUM_BINS 1000
+#define LLONG_MAX 9223372036854775807LL
 #endif
 
 #ifndef HISTOGRAM_DEFAULT_BIN_WIDTH
 /* 1048576 = 2^20 ^= 1/1024 s */
-# define HISTOGRAM_DEFAULT_BIN_WIDTH 1048576
+#define HISTOGRAM_DEFAULT_BIN_WIDTH 1048576
 #endif
 
-struct latency_counter_s
-{
+struct latency_counter_s {
   cdtime_t start_time;
 
   cdtime_t sum;
@@ -70,14 +65,14 @@ struct latency_counter_s
 * When a value above this range is added, Histogram's range is increased by
 * increasing the bin width (note that number of bins remains always at 1000).
 * This operation of increasing bin width is little expensive as each bin need
-* to be visited to update it's count. To reduce frequent change of bin width,
+* to be visited to update its count. To reduce frequent change of bin width,
 * new bin width will be the next nearest power of 2. Example: 2, 4, 8, 16, 32,
 * 64, 128, 256, 512, 1024, 2048, 5086, ...
 *
 * So, if the required bin width is 300, then new bin width will be 512 as it is
 * the next nearest power of 2.
 */
-static void change_bin_width (latency_counter_t *lc, cdtime_t latency) /* {{{ */
+static void change_bin_width(latency_counter_t *lc, cdtime_t latency) /* {{{ */
 {
   /* This function is called because the new value is above histogram's range.
    * First find the required bin width:
@@ -85,9 +80,11 @@ static void change_bin_width (latency_counter_t *lc, cdtime_t latency) /* {{{ */
    * then get the next nearest power of 2
    *           newBinWidth = 2^(ceil(log2(requiredBinWidth)))
    */
-  double required_bin_width = ((double) (latency + 1)) / ((double) HISTOGRAM_NUM_BINS);
-  double required_bin_width_logbase2 = log (required_bin_width) / log (2.0);
-  cdtime_t new_bin_width = (cdtime_t) (pow (2.0, ceil (required_bin_width_logbase2)) + .5);
+  double required_bin_width =
+      ((double)(latency + 1)) / ((double)HISTOGRAM_NUM_BINS);
+  double required_bin_width_logbase2 = log(required_bin_width) / log(2.0);
+  cdtime_t new_bin_width =
+      (cdtime_t)(pow(2.0, ceil(required_bin_width_logbase2)) + .5);
   cdtime_t old_bin_width = lc->bin_width;
 
   lc->bin_width = new_bin_width;
@@ -96,50 +93,49 @@ static void change_bin_width (latency_counter_t *lc, cdtime_t latency) /* {{{ */
    * old bin's count to new bin. */
   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);
-
-      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)
-             continue;
-         assert (new_bin < i);
-
-         lc->histogram[new_bin] += lc->histogram[i];
-         lc->histogram[i] = 0;
-      }
+    double width_change_ratio =
+        ((double)old_bin_width) / ((double)new_bin_width);
+
+    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)
+        continue;
+      assert(new_bin < i);
+
+      lc->histogram[new_bin] += lc->histogram[i];
+      lc->histogram[i] = 0;
+    }
   }
 
   DEBUG("utils_latency: change_bin_width: latency = %.3f; "
-      "old_bin_width = %.3f; new_bin_width = %.3f;",
-      CDTIME_T_TO_DOUBLE (latency),
-      CDTIME_T_TO_DOUBLE (old_bin_width),
-      CDTIME_T_TO_DOUBLE (new_bin_width));
+        "old_bin_width = %.3f; new_bin_width = %.3f;",
+        CDTIME_T_TO_DOUBLE(latency), CDTIME_T_TO_DOUBLE(old_bin_width),
+        CDTIME_T_TO_DOUBLE(new_bin_width));
 } /* }}} void change_bin_width */
 
-latency_counter_t *latency_counter_create (void) /* {{{ */
+latency_counter_t *latency_counter_create(void) /* {{{ */
 {
   latency_counter_t *lc;
 
-  lc = calloc (1, sizeof (*lc));
+  lc = calloc(1, sizeof(*lc));
   if (lc == NULL)
-    return (NULL);
+    return NULL;
 
   lc->bin_width = HISTOGRAM_DEFAULT_BIN_WIDTH;
-  latency_counter_reset (lc);
-  return (lc);
+  latency_counter_reset(lc);
+  return lc;
 } /* }}} latency_counter_t *latency_counter_create */
 
-void latency_counter_destroy (latency_counter_t *lc) /* {{{ */
+void latency_counter_destroy(latency_counter_t *lc) /* {{{ */
 {
-  sfree (lc);
+  sfree(lc);
 } /* }}} void latency_counter_destroy */
 
-void latency_counter_add (latency_counter_t *lc, cdtime_t latency) /* {{{ */
+void latency_counter_add(latency_counter_t *lc, cdtime_t latency) /* {{{ */
 {
   cdtime_t bin;
 
-  if ((lc == NULL) || (latency == 0) || (latency > ((cdtime_t) LLONG_MAX)))
+  if ((lc == NULL) || (latency == 0) || (latency > ((cdtime_t)LLONG_MAX)))
     return;
 
   lc->sum += latency;
@@ -156,20 +152,18 @@ void latency_counter_add (latency_counter_t *lc, cdtime_t latency) /* {{{ */
    * subtract one from the cdtime_t value so that exactly 1.0 ms get sorted
    * accordingly. */
   bin = (latency - 1) / lc->bin_width;
-  if (bin >= HISTOGRAM_NUM_BINS)
-  {
-      change_bin_width (lc, latency);
-      bin = (latency - 1) / lc->bin_width;
-      if (bin >= HISTOGRAM_NUM_BINS)
-      {
-          ERROR ("utils_latency: latency_counter_add: Invalid bin: %"PRIu64, bin);
-          return;
-      }
+  if (bin >= HISTOGRAM_NUM_BINS) {
+    change_bin_width(lc, latency);
+    bin = (latency - 1) / lc->bin_width;
+    if (bin >= HISTOGRAM_NUM_BINS) {
+      ERROR("utils_latency: latency_counter_add: Invalid bin: %" PRIu64, bin);
+      return;
+    }
   }
   lc->histogram[bin]++;
 } /* }}} void latency_counter_add */
 
-void latency_counter_reset (latency_counter_t *lc) /* {{{ */
+void latency_counter_reset(latency_counter_t *lc) /* {{{ */
 {
   if (lc == NULL)
     return;
@@ -183,69 +177,65 @@ void latency_counter_reset (latency_counter_t *lc) /* {{{ */
   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))
-  {
+  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));
+          "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));
+  memset(lc, 0, sizeof(*lc));
 
   /* preserve bin width */
   lc->bin_width = bin_width;
-  lc->start_time = cdtime ();
+  lc->start_time = cdtime();
 } /* }}} void latency_counter_reset */
 
-cdtime_t latency_counter_get_min (latency_counter_t *lc) /* {{{ */
+cdtime_t latency_counter_get_min(latency_counter_t *lc) /* {{{ */
 {
   if (lc == NULL)
-    return (0);
-  return (lc->min);
+    return 0;
+  return lc->min;
 } /* }}} cdtime_t latency_counter_get_min */
 
-cdtime_t latency_counter_get_max (latency_counter_t *lc) /* {{{ */
+cdtime_t latency_counter_get_max(latency_counter_t *lc) /* {{{ */
 {
   if (lc == NULL)
-    return (0);
-  return (lc->max);
+    return 0;
+  return lc->max;
 } /* }}} cdtime_t latency_counter_get_max */
 
-cdtime_t latency_counter_get_sum (latency_counter_t *lc) /* {{{ */
+cdtime_t latency_counter_get_sum(latency_counter_t *lc) /* {{{ */
 {
   if (lc == NULL)
-    return (0);
-  return (lc->sum);
+    return 0;
+  return lc->sum;
 } /* }}} cdtime_t latency_counter_get_sum */
 
-size_t latency_counter_get_num (latency_counter_t *lc) /* {{{ */
+size_t latency_counter_get_num(latency_counter_t *lc) /* {{{ */
 {
   if (lc == NULL)
-    return (0);
-  return (lc->num);
+    return 0;
+  return lc->num;
 } /* }}} size_t latency_counter_get_num */
 
-cdtime_t latency_counter_get_average (latency_counter_t *lc) /* {{{ */
+cdtime_t latency_counter_get_average(latency_counter_t *lc) /* {{{ */
 {
   double average;
 
   if ((lc == NULL) || (lc->num == 0))
-    return (0);
+    return 0;
 
-  average = CDTIME_T_TO_DOUBLE (lc->sum) / ((double) lc->num);
-  return (DOUBLE_TO_CDTIME_T (average));
+  average = CDTIME_T_TO_DOUBLE(lc->sum) / ((double)lc->num);
+  return DOUBLE_TO_CDTIME_T(average);
 } /* }}} cdtime_t latency_counter_get_average */
 
-cdtime_t latency_counter_get_percentile (latency_counter_t *lc, /* {{{ */
-    double percent)
-{
+cdtime_t latency_counter_get_percentile(latency_counter_t *lc, /* {{{ */
+                                        double percent) {
   double percent_upper;
   double percent_lower;
   double p;
@@ -255,126 +245,100 @@ cdtime_t latency_counter_get_percentile (latency_counter_t *lc, /* {{{ */
   size_t i;
 
   if ((lc == NULL) || (lc->num == 0) || !((percent > 0.0) && (percent < 100.0)))
-    return (0);
+    return 0;
 
   /* Find index i so that at least "percent" events are within i+1 ms. */
   percent_upper = 0.0;
   percent_lower = 0.0;
   sum = 0;
-  for (i = 0; i < HISTOGRAM_NUM_BINS; i++)
-  {
+  for (i = 0; i < HISTOGRAM_NUM_BINS; i++) {
     percent_lower = percent_upper;
     sum += lc->histogram[i];
     if (sum == 0)
       percent_upper = 0.0;
     else
-      percent_upper = 100.0 * ((double) sum) / ((double) lc->num);
+      percent_upper = 100.0 * ((double)sum) / ((double)lc->num);
 
     if (percent_upper >= percent)
       break;
   }
 
   if (i >= HISTOGRAM_NUM_BINS)
-    return (0);
+    return 0;
 
-  assert (percent_upper >= percent);
-  assert (percent_lower < percent);
+  assert(percent_upper >= percent);
+  assert(percent_lower < percent);
 
   if (i == 0)
-    return (lc->bin_width);
+    return lc->bin_width;
 
-  latency_lower = ((cdtime_t) i) * lc->bin_width;
+  latency_lower = ((cdtime_t)i) * lc->bin_width;
   p = (percent - percent_lower) / (percent_upper - percent_lower);
 
-  latency_interpolated = latency_lower
-    + DOUBLE_TO_CDTIME_T (p * CDTIME_T_TO_DOUBLE (lc->bin_width));
+  latency_interpolated =
+      latency_lower + DOUBLE_TO_CDTIME_T(p * CDTIME_T_TO_DOUBLE(lc->bin_width));
 
-  DEBUG ("latency_counter_get_percentile: latency_interpolated = %.3f",
-      CDTIME_T_TO_DOUBLE (latency_interpolated));
-  return (latency_interpolated);
+  DEBUG("latency_counter_get_percentile: latency_interpolated = %.3f",
+        CDTIME_T_TO_DOUBLE(latency_interpolated));
+  return latency_interpolated;
 } /* }}} cdtime_t latency_counter_get_percentile */
 
-cdtime_t latency_counter_get_start_time (const latency_counter_t *lc) /* {{{ */
-{
-  if (lc == NULL)
-    return (0);
-
-  return lc->start_time;
-} /* }}} cdtime_t latency_counter_get_start_time */
-
-/*
- * NAME
- *  latency_counter_get_rate(counter,lower,upper,now)
- *
- * DESCRIPTION
- *   Calculates rate of latency values fall within requested interval.
- *   Interval specified as [lower,upper] (including boundaries).
- *   When upper value is equal to 0 then interval is [lower, infinity).
- */
-
-double latency_counter_get_rate (const latency_counter_t *lc, /* {{{ */
-        cdtime_t lower, cdtime_t upper, const cdtime_t now)
-{
-  cdtime_t lower_bin;
-  cdtime_t upper_bin;
-  double sum = 0;
-
+double latency_counter_get_rate(const latency_counter_t *lc, /* {{{ */
+                                cdtime_t lower, cdtime_t upper,
+                                const cdtime_t now) {
   if ((lc == NULL) || (lc->num == 0))
-    return (0);
-
-  if (lower < 1) {
-    //sum += lc->zero;
-    //lower = 1;
-    return (0);
-  }
+    return NAN;
 
   if (upper && (upper < lower))
-    return (0);
-
-  /* A latency of _exactly_ 1.0 ms is stored in the buffer 0 */
-  lower_bin = (lower - 1) / lc->bin_width;
+    return NAN;
+  if (lower == upper)
+    return 0;
+
+  /* Buckets have an exclusive lower bound and an inclusive upper bound. That
+   * means that the first bucket, index 0, represents (0-bin_width]. That means
+   * that latency==bin_width needs to result in bin=0, that's why we need to
+   * subtract one before dividing by bin_width. */
+  cdtime_t lower_bin = 0;
+  if (lower)
+    /* lower is *exclusive* => determine bucket for lower+1 */
+    lower_bin = ((lower + 1) - 1) / lc->bin_width;
+
+  /* lower is greater than the longest latency observed => rate is zero. */
+  if (lower_bin >= HISTOGRAM_NUM_BINS)
+    return 0;
 
+  cdtime_t upper_bin = HISTOGRAM_NUM_BINS - 1;
   if (upper)
     upper_bin = (upper - 1) / lc->bin_width;
-  else
-    upper_bin = HISTOGRAM_NUM_BINS - 1;
-
-  if (lower_bin >= HISTOGRAM_NUM_BINS)
-    lower_bin = HISTOGRAM_NUM_BINS - 1;
 
   if (upper_bin >= HISTOGRAM_NUM_BINS) {
     upper_bin = HISTOGRAM_NUM_BINS - 1;
     upper = 0;
   }
 
-  sum = 0;
+  double sum = 0;
   for (size_t i = lower_bin; i <= upper_bin; i++)
-  {
     sum += lc->histogram[i];
-  }
 
-  /* Approximate ratio of requests below "lower" */
-  cdtime_t lower_bin_boundary = lower_bin * lc->bin_width;
-
-  /* When bin width is 0.125 (for example), then bin 0 stores
-   * values for interval [0, 0.124) (excluding).
-   * With lower = 0.100, the ratio should be 0.099 / 0.125.
-   * I.e. ratio = 0.100 - 0.000 - 0.001
-   */
-  double ratio = (double)(lower - lower_bin_boundary - DOUBLE_TO_CDTIME_T(0.001))
-                  / (double)lc->bin_width;
-  sum -= ratio * lc->histogram[lower_bin];
+  if (lower) {
+    /* Approximate ratio of requests in lower_bin, that fall between
+     * lower_bin_boundary and lower. This ratio is then subtracted from sum to
+     * increase accuracy. */
+    cdtime_t lower_bin_boundary = lower_bin * lc->bin_width;
+    assert(lower >= lower_bin_boundary);
+    double lower_ratio =
+        (double)(lower - lower_bin_boundary) / ((double)lc->bin_width);
+    sum -= lower_ratio * lc->histogram[lower_bin];
+  }
 
-  /* Approximate ratio of requests above "upper" */
-  cdtime_t upper_bin_boundary = (upper_bin + 1) * lc->bin_width;
-  if (upper)
-  {
-    assert (upper <= upper_bin_boundary);
+  if (upper) {
+    /* As above: approximate ratio of requests in upper_bin, that fall between
+     * upper and upper_bin_boundary. */
+    cdtime_t upper_bin_boundary = (upper_bin + 1) * lc->bin_width;
+    assert(upper <= upper_bin_boundary);
     double ratio = (double)(upper_bin_boundary - upper) / (double)lc->bin_width;
     sum -= ratio * lc->histogram[upper_bin];
   }
 
-  return sum / (CDTIME_T_TO_DOUBLE (now - lc->start_time));
+  return sum / (CDTIME_T_TO_DOUBLE(now - lc->start_time));
 } /* }}} double latency_counter_get_rate */
-
-/* vim: set sw=2 sts=2 et fdm=marker : */