X-Git-Url: https://git.octo.it/?p=collectd.git;a=blobdiff_plain;f=src%2Futils_latency.c;h=1d3bf2e97c5a749e5ff4fb1b4fef91ecb115f1dc;hp=651547ab22af54beebe1cc9ee05d1e3f8b7c56f7;hb=06a86a60a7dabc685bdbd81ce3d36ea5f7e2c2d4;hpb=79963d13c1884d1d92667cc502ad20758b084a12

diff --git a/src/utils_latency.c b/src/utils_latency.c
index 651547ab..1d3bf2e9 100644
--- a/src/utils_latency.c
+++ b/src/utils_latency.c
@@ -37,10 +37,6 @@
 #define LLONG_MAX 9223372036854775807LL
 #endif
 
-#ifndef HISTOGRAM_NUM_BINS
-#define HISTOGRAM_NUM_BINS 1000
-#endif
-
 #ifndef HISTOGRAM_DEFAULT_BIN_WIDTH
 /* 1048576 = 2^20 ^= 1/1024 s */
 #define HISTOGRAM_DEFAULT_BIN_WIDTH 1048576
@@ -69,7 +65,7 @@ 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, ...
 *
@@ -123,11 +119,11 @@ latency_counter_t *latency_counter_create(void) /* {{{ */
 
   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);
+  return lc;
 } /* }}} latency_counter_t *latency_counter_create */
 
 void latency_counter_destroy(latency_counter_t *lc) /* {{{ */
@@ -152,7 +148,7 @@ void latency_counter_add(latency_counter_t *lc, cdtime_t latency) /* {{{ */
   if (lc->max < latency)
     lc->max = latency;
 
-  /* A latency of _exactly_ 1.0 ms should be stored in the buffer 0, so
+  /* A latency of _exactly_ 1.0 ms is stored in the buffer 0, so
    * subtract one from the cdtime_t value so that exactly 1.0 ms get sorted
    * accordingly. */
   bin = (latency - 1) / lc->bin_width;
@@ -202,29 +198,29 @@ void latency_counter_reset(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) /* {{{ */
 {
   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) /* {{{ */
 {
   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) /* {{{ */
 {
   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) /* {{{ */
@@ -232,10 +228,10 @@ 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));
+  return DOUBLE_TO_CDTIME_T(average);
 } /* }}} cdtime_t latency_counter_get_average */
 
 cdtime_t latency_counter_get_percentile(latency_counter_t *lc, /* {{{ */
@@ -249,7 +245,7 @@ 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;
@@ -268,13 +264,13 @@ cdtime_t latency_counter_get_percentile(latency_counter_t *lc, /* {{{ */
   }
 
   if (i >= HISTOGRAM_NUM_BINS)
-    return (0);
+    return 0;
 
   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;
   p = (percent - percent_lower) / (percent_upper - percent_lower);
@@ -284,7 +280,65 @@ cdtime_t latency_counter_get_percentile(latency_counter_t *lc, /* {{{ */
 
   DEBUG("latency_counter_get_percentile: latency_interpolated = %.3f",
         CDTIME_T_TO_DOUBLE(latency_interpolated));
-  return (latency_interpolated);
+  return latency_interpolated;
 } /* }}} cdtime_t latency_counter_get_percentile */
 
-/* vim: set sw=2 sts=2 et fdm=marker : */
+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 NAN;
+
+  if (upper && (upper < lower))
+    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;
+
+  if (upper_bin >= HISTOGRAM_NUM_BINS) {
+    upper_bin = HISTOGRAM_NUM_BINS - 1;
+    upper = 0;
+  }
+
+  double sum = 0;
+  for (size_t i = lower_bin; i <= upper_bin; i++)
+    sum += lc->histogram[i];
+
+  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];
+  }
+
+  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));
+} /* }}} double latency_counter_get_rate */