#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
* 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, ...
*
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) /* {{{ */
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;
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) /* {{{ */
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, /* {{{ */
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;
}
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);
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 */
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