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, /* {{{ */
- 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);
+ 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 lower==bin_width needs to result in lower_bin=0, hence the -1. */
+ * 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_bin = (lower - 1) / lc->bin_width;
- else
- lower_bin = 0;
+ /* 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];
- }
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 - 1) / ((double) 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)
- {
+ 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);
+ 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 : */