X-Git-Url: https://git.verplant.org/?a=blobdiff_plain;f=src%2Futils_latency.c;h=5749f10da199700c0b18e0c36020e6f2f9c072a1;hb=936c450a86c841eea89888c8550c9118fae90c25;hp=71707ada83fdaa6f970510f803733ba446f64411;hpb=9515f607aa5d401e288b26d64e2f90f6ea4dd6fe;p=collectd.git

diff --git a/src/utils_latency.c b/src/utils_latency.c
index 71707ada..5749f10d 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
@@ -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;
@@ -294,131 +290,64 @@ cdtime_t latency_counter_get_percentile (latency_counter_t *lc, /* {{{ */
   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 */
-
-double latency_counter_get_rate (const latency_counter_t *lc, /* {{{ */
-        const cdtime_t lower, cdtime_t upper, const cdtime_t now)
-{
-  cdtime_t lower_bin;
-  cdtime_t upper_bin;
-  double p;
-  double sum = 0;
-  size_t i;
-
+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 (NAN);
+  if (lower == upper)
     return (0);
 
-  /* A latency of _exactly_ 1.0 ms should be stored in the buffer 0 */
-  lower_bin = (lower - 1) / lc->bin_width;
+  /* 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;
   }
 
-  ERROR("get_rate (%.3f, %.3f): bin_width = %.3f; "
-      "lower_bin = %"PRIu64" (%.3f); upper_bin = %"PRIu64" (%.3f);",
-      CDTIME_T_TO_DOUBLE (lower),
-      CDTIME_T_TO_DOUBLE (upper),
-      CDTIME_T_TO_DOUBLE (lc->bin_width),
-      lower_bin,
-      CDTIME_T_TO_DOUBLE (lc->bin_width * lower_bin),
-      upper_bin,
-      CDTIME_T_TO_DOUBLE (lc->bin_width * upper_bin)
-  );
-
-  sum = 0;
-  for (i = lower_bin; i <= upper_bin; i++)
-  {
-    ERROR("SUMM, bin: %d (%.3f), v: %d", i, CDTIME_T_TO_DOUBLE(i * lc->bin_width), lc->histogram[i]);
+  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];
   }
-  ERROR("sum before interpolations: %.3f", sum);
-
-  //v1//p = ((double)lower - (double)(lower_bin + 1) * (double)lc->bin_width) / (double)lc->bin_width;
-  p = ((double)lower - (double)(lower_bin + 0) * (double)lc->bin_width - (double)DOUBLE_TO_CDTIME_T(0.001)) / (double)lc->bin_width;
-  ERROR("interpolation 1: p=%lf, 1=%"PRIu64" (%.3f), 2=%"PRIu64" (%.3f), 3=%"PRIu64" (%.3f); lower_bin: %"PRIu64"",
-     p,
-     //1
-     lower - DOUBLE_TO_CDTIME_T(0.001),
-     CDTIME_T_TO_DOUBLE (lower - (double)DOUBLE_TO_CDTIME_T(0.001)),
-     //2
-     (lower_bin + 0) * lc->bin_width,
-     CDTIME_T_TO_DOUBLE ((lower_bin + 0) * lc->bin_width),
-     //3
-     lc->bin_width,
-     CDTIME_T_TO_DOUBLE (lc->bin_width),
-     lower_bin
-  );
-  sum -= p * lc->histogram[lower_bin];
-/*
-  if (upper && upper_bin == lower_bin) {
-    //p = ((double)(upper_bin + 1) * (double)lc->bin_width - (double)upper) / (double)lc->bin_width;
-    p = (double)(upper_bin + 1) - (double)upper / (double)lc->bin_width;
-    ERROR("interpolation 2: p=%lf, 1=%"PRIu64" (%.3f), 2=%"PRIu64" (%.3f), 3=%.3f (%.3f); upper_bin: %"PRIu64"",
-       p,
-       //1
-       (upper_bin + 1) * lc->bin_width,
-       CDTIME_T_TO_DOUBLE ((upper_bin + 1) * lc->bin_width),
-       //2
-       upper,
-       CDTIME_T_TO_DOUBLE (upper),
-       //3
-       (double)lc->bin_width,
-       CDTIME_T_TO_DOUBLE (lc->bin_width),
-       upper_bin
-    );
-    sum -= p * lc->histogram[upper_bin];
-  }
-  else 
-  */
-  if (upper && upper < (upper_bin + 1) * lc->bin_width)
-  {
-    // p = ((upper_bin + 1) * bin_width - upper ) / bin_width;
-
-    //p = ((double)upper - (double)(upper_bin + 0) * (double)lc->bin_width) / (double)lc->bin_width;
-    p = ((double)(upper_bin + 1) * (double)lc->bin_width - (double)upper) / (double)lc->bin_width;
-    ERROR("interpolation 3: p=%lf, 1=%"PRIu64" (%.3f), 2=%"PRIu64" (%.3f), 3=%"PRIu64" (%.3f); upper_bin: %"PRIu64"",
-       p,
-       //1
-       (upper_bin + 1) * lc->bin_width,
-       CDTIME_T_TO_DOUBLE ((upper_bin + 1) * lc->bin_width),
-       //2
-       upper,
-       CDTIME_T_TO_DOUBLE (upper),
-       //3
-       lc->bin_width,
-       CDTIME_T_TO_DOUBLE (lc->bin_width),
-       upper_bin
-    );
-    sum -= p * lc->histogram[upper_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));
 
+  return sum / (CDTIME_T_TO_DOUBLE(now - lc->start_time));
 } /* }}} double latency_counter_get_rate */
 
-
 /* vim: set sw=2 sts=2 et fdm=marker : */