X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=src%2Futils_latency.c;h=7a607e430de7112f56c342cf956409eb4c5e1728;hb=8c61dbce195987d352034663204d5df32776e9cb;hp=12fc9b82dfa6e1e3817184d6027ef7f4b724fbee;hpb=d8a02e6c6f5875dfcab7b011d1f340e3a13c9e39;p=collectd.git diff --git a/src/utils_latency.c b/src/utils_latency.c index 12fc9b82..1a82eab6 100644 --- a/src/utils_latency.c +++ b/src/utils_latency.c @@ -25,6 +25,7 @@ **/ #include "collectd.h" + #include "plugin.h" #include "utils_latency.h" #include "common.h" @@ -36,10 +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 @@ -76,7 +73,7 @@ struct latency_counter_s * So, if the required bin width is 300, then new bin width will be 512 as it is * the next nearest power of 2. */ -void change_bin_width (latency_counter_t *lc, cdtime_t latency) /* {{{ */ +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: @@ -96,9 +93,8 @@ void change_bin_width (latency_counter_t *lc, cdtime_t latency) /* {{{ */ 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); - size_t i; - for (i = 0; i < HISTOGRAM_NUM_BINS; i++) + 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) @@ -117,17 +113,16 @@ void change_bin_width (latency_counter_t *lc, cdtime_t latency) /* {{{ */ CDTIME_T_TO_DOUBLE (new_bin_width)); } /* }}} void change_bin_width */ -latency_counter_t *latency_counter_create () /* {{{ */ +latency_counter_t *latency_counter_create (void) /* {{{ */ { latency_counter_t *lc; - lc = malloc (sizeof (*lc)); + lc = calloc (1, sizeof (*lc)); if (lc == NULL) return (NULL); - memset (lc, 0, sizeof (*lc)); - latency_counter_reset (lc); lc->bin_width = HISTOGRAM_DEFAULT_BIN_WIDTH; + latency_counter_reset (lc); return (lc); } /* }}} latency_counter_t *latency_counter_create */ @@ -153,7 +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; @@ -176,6 +171,28 @@ void latency_counter_reset (latency_counter_t *lc) /* {{{ */ 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 */ @@ -273,4 +290,76 @@ 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, /* {{{ */ + cdtime_t lower, cdtime_t upper, const cdtime_t now) +{ + cdtime_t lower_bin; + cdtime_t upper_bin; + double sum = 0; + + if ((lc == NULL) || (lc->num == 0)) + return (0); + + if (upper && (upper < lower)) + 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. */ + if (lower) + lower_bin = (lower - 1) / lc->bin_width; + else + lower_bin = 0; + + 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; + 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); + 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 */ + /* vim: set sw=2 sts=2 et fdm=marker : */