X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=src%2Futils_latency.c;h=91ddd5fd92485c0a02d6642b56ce346334f40b50;hb=master;hp=1d3bf2e97c5a749e5ff4fb1b4fef91ecb115f1dc;hpb=b9b5e5d573d0011c4f3276e9b84b73ba4dd2e870;p=collectd.git diff --git a/src/utils_latency.c b/src/utils_latency.c deleted file mode 100644 index 1d3bf2e9..00000000 --- a/src/utils_latency.c +++ /dev/null @@ -1,344 +0,0 @@ -/** - * collectd - src/utils_latency.c - * Copyright (C) 2013 Florian Forster - * - * Permission is hereby granted, free of charge, to any person obtaining a - * copy of this software and associated documentation files (the "Software"), - * to deal in the Software without restriction, including without limitation - * the rights to use, copy, modify, merge, publish, distribute, sublicense, - * and/or sell copies of the Software, and to permit persons to whom the - * Software is furnished to do so, subject to the following conditions: - * - * The above copyright notice and this permission notice shall be included in - * all copies or substantial portions of the Software. - * - * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR - * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, - * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE - * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER - * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING - * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER - * DEALINGS IN THE SOFTWARE. - * - * Authors: - * Florian Forster - **/ - -#include "collectd.h" - -#include "common.h" -#include "plugin.h" -#include "utils_latency.h" - -#include -#include - -#ifndef LLONG_MAX -#define LLONG_MAX 9223372036854775807LL -#endif - -#ifndef HISTOGRAM_DEFAULT_BIN_WIDTH -/* 1048576 = 2^20 ^= 1/1024 s */ -#define HISTOGRAM_DEFAULT_BIN_WIDTH 1048576 -#endif - -struct latency_counter_s { - cdtime_t start_time; - - cdtime_t sum; - size_t num; - - cdtime_t min; - cdtime_t max; - - cdtime_t bin_width; - int histogram[HISTOGRAM_NUM_BINS]; -}; - -/* -* Histogram represents the distribution of data, it has a list of "bins". -* Each bin represents an interval and has a count (frequency) of -* number of values fall within its interval. -* -* Histogram's range is determined by the number of bins and the bin width, -* There are 1000 bins and all bins have the same width of default 1 millisecond. -* 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 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) /* {{{ */ -{ - /* This function is called because the new value is above histogram's range. - * First find the required bin width: - * requiredBinWidth = (value + 1) / numBins - * 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); - cdtime_t old_bin_width = lc->bin_width; - - lc->bin_width = new_bin_width; - - /* bin_width has been increased, now iterate through all bins and move the - * 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; - } - } - - 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)); -} /* }}} void change_bin_width */ - -latency_counter_t *latency_counter_create(void) /* {{{ */ -{ - latency_counter_t *lc; - - lc = calloc(1, sizeof(*lc)); - if (lc == NULL) - return NULL; - - lc->bin_width = HISTOGRAM_DEFAULT_BIN_WIDTH; - latency_counter_reset(lc); - return lc; -} /* }}} latency_counter_t *latency_counter_create */ - -void latency_counter_destroy(latency_counter_t *lc) /* {{{ */ -{ - sfree(lc); -} /* }}} void latency_counter_destroy */ - -void latency_counter_add(latency_counter_t *lc, cdtime_t latency) /* {{{ */ -{ - cdtime_t bin; - - if ((lc == NULL) || (latency == 0) || (latency > ((cdtime_t)LLONG_MAX))) - return; - - lc->sum += latency; - lc->num++; - - if ((lc->min == 0) && (lc->max == 0)) - lc->min = lc->max = latency; - if (lc->min > latency) - lc->min = latency; - if (lc->max < latency) - lc->max = latency; - - /* 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; - 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) /* {{{ */ -{ - if (lc == NULL) - return; - - cdtime_t bin_width = lc->bin_width; - cdtime_t max_bin = (lc->max - 1) / lc->bin_width; - -/* - If max latency is REDUCE_THRESHOLD times less than histogram's range, - then cut it in half. REDUCE_THRESHOLD must be >= 2. - 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)) { - /* 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)); - } - - memset(lc, 0, sizeof(*lc)); - - /* preserve bin width */ - lc->bin_width = bin_width; - lc->start_time = cdtime(); -} /* }}} void latency_counter_reset */ - -cdtime_t latency_counter_get_min(latency_counter_t *lc) /* {{{ */ -{ - if (lc == NULL) - 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; -} /* }}} cdtime_t latency_counter_get_max */ - -cdtime_t latency_counter_get_sum(latency_counter_t *lc) /* {{{ */ -{ - if (lc == NULL) - 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; -} /* }}} 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; - - 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) { - double percent_upper; - double percent_lower; - double p; - cdtime_t latency_lower; - cdtime_t latency_interpolated; - int sum; - size_t i; - - if ((lc == NULL) || (lc->num == 0) || !((percent > 0.0) && (percent < 100.0))) - 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++) { - 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); - - if (percent_upper >= percent) - break; - } - - if (i >= HISTOGRAM_NUM_BINS) - return 0; - - assert(percent_upper >= percent); - assert(percent_lower < percent); - - if (i == 0) - return 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)); - - DEBUG("latency_counter_get_percentile: latency_interpolated = %.3f", - CDTIME_T_TO_DOUBLE(latency_interpolated)); - return latency_interpolated; -} /* }}} cdtime_t latency_counter_get_percentile */ - -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 */