From a5e8962a14936b89ba8523e77cff2af5a79f16b8 Mon Sep 17 00:00:00 2001 From: Florian Forster Date: Mon, 13 Jul 2015 11:53:58 +0200 Subject: [PATCH] src/utils_latency.c: Store "bin_width" as cdtime_t. This solves the integer overflow when passing huge latency values to latency_counter_add(). In addition to fixing the overflow the function will now ignore values that are larger than LLONG_MAX, i.e. the longest possible latency is 272 years. As a nice side-effect, the precission of latency_counter_get_percentile() is improved. Issue: #1131 --- src/utils_latency.c | 77 ++++++++++++++++++++++----------------------- 1 file changed, 38 insertions(+), 39 deletions(-) diff --git a/src/utils_latency.c b/src/utils_latency.c index 5d3b1468..d570ab69 100644 --- a/src/utils_latency.c +++ b/src/utils_latency.c @@ -30,12 +30,16 @@ #include "common.h" #include +#include #ifndef HISTOGRAM_NUM_BINS # define HISTOGRAM_NUM_BINS 1000 #endif -static const int HISTOGRAM_DEFAULT_BIN_WIDTH = 1; +#ifndef HISTOGRAM_DEFAULT_BIN_WIDTH +/* 1048576 = 2^20 ^= 1/1024 s */ +# define HISTOGRAM_DEFAULT_BIN_WIDTH 1048576 +#endif struct latency_counter_s { @@ -47,7 +51,7 @@ struct latency_counter_s cdtime_t min; cdtime_t max; - int bin_width; + cdtime_t bin_width; int histogram[HISTOGRAM_NUM_BINS]; }; @@ -68,7 +72,7 @@ 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, size_t val) /* {{{ */ +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: @@ -76,17 +80,15 @@ void change_bin_width (latency_counter_t *lc, size_t val) /* {{{ */ * then get the next nearest power of 2 * newBinWidth = 2^(ceil(log2(requiredBinWidth))) */ - double required_bin_width = (double)(val + 1) / HISTOGRAM_NUM_BINS; - double required_bin_width_logbase2 = log(required_bin_width) / log(2.0); - int new_bin_width = (int)(pow(2.0, ceil( required_bin_width_logbase2))); - int old_bin_width = lc->bin_width; + 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. - */ + /* 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); @@ -99,19 +101,16 @@ void change_bin_width (latency_counter_t *lc, size_t val) /* {{{ */ continue; assert (new_bin < i); - if (lc->histogram[i] != 0) { - DEBUG ("utils_latency: moving %d from %zu to %zu.", lc->histogram[i], i, new_bin); - } lc->histogram[new_bin] += lc->histogram[i]; lc->histogram[i] = 0; } } - DEBUG("utils_latency: change_bin_width: val-[%zu], oldBinWidth-[%d], " - "newBinWidth-[%d], required_bin_width-[%f], " - "required_bin_width_logbase2-[%f]", - val, old_bin_width, new_bin_width, required_bin_width, - required_bin_width_logbase2); + 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 () /* {{{ */ @@ -135,9 +134,9 @@ void latency_counter_destroy (latency_counter_t *lc) /* {{{ */ void latency_counter_add (latency_counter_t *lc, cdtime_t latency) /* {{{ */ { - size_t latency_ms; + cdtime_t bin; - if ((lc == NULL) || (latency == 0)) + if ((lc == NULL) || (latency == 0) || (latency > ((cdtime_t) LLONG_MAX))) return; lc->sum += latency; @@ -153,16 +152,14 @@ void latency_counter_add (latency_counter_t *lc, cdtime_t latency) /* {{{ */ /* A latency of _exactly_ 1.0 ms should be stored in the buffer 0, so * subtract one from the cdtime_t value so that exactly 1.0 ms get sorted * accordingly. */ - latency_ms = (size_t) CDTIME_T_TO_MS (latency - 1); - - int bin = (int)(latency_ms / lc->bin_width); + bin = (latency - 1) / lc->bin_width; if (bin >= HISTOGRAM_NUM_BINS) { - change_bin_width(lc, latency_ms); - bin = (int)(latency_ms / lc->bin_width); + change_bin_width (lc, latency); + bin = (latency - 1) / lc->bin_width; if (bin >= HISTOGRAM_NUM_BINS) { - ERROR("utils_latency: latency_counter_add: Invalid bin %d", bin); + ERROR ("utils_latency: latency_counter_add: Invalid bin %lu", bin); return; } } @@ -174,7 +171,7 @@ void latency_counter_reset (latency_counter_t *lc) /* {{{ */ if (lc == NULL) return; - int bin_width = lc->bin_width; + cdtime_t bin_width = lc->bin_width; memset (lc, 0, sizeof (*lc)); /* preserve bin width */ @@ -221,14 +218,14 @@ cdtime_t latency_counter_get_average (latency_counter_t *lc) /* {{{ */ return (DOUBLE_TO_CDTIME_T (average)); } /* }}} cdtime_t latency_counter_get_average */ -cdtime_t latency_counter_get_percentile (latency_counter_t *lc, +cdtime_t latency_counter_get_percentile (latency_counter_t *lc, /* {{{ */ double percent) { double percent_upper; double percent_lower; - double ms_upper; - double ms_lower; - double ms_interpolated; + double p; + cdtime_t latency_lower; + cdtime_t latency_interpolated; int sum; size_t i; @@ -258,16 +255,18 @@ cdtime_t latency_counter_get_percentile (latency_counter_t *lc, assert (percent_upper >= percent); assert (percent_lower < percent); - ms_upper = (double) ( (i + 1) * lc->bin_width ); - ms_lower = (double) ( i * lc->bin_width ); if (i == 0) - return (MS_TO_CDTIME_T (ms_upper)); + return (lc->bin_width); + + latency_lower = ((cdtime_t) i) * lc->bin_width; + p = (percent - percent_lower) / (percent_upper - percent_lower); - ms_interpolated = (((percent_upper - percent) * ms_lower) - + ((percent - percent_lower) * ms_upper)) - / (percent_upper - percent_lower); + latency_interpolated = latency_lower + + DOUBLE_TO_CDTIME_T (p * CDTIME_T_TO_DOUBLE (lc->bin_width)); - return (MS_TO_CDTIME_T (ms_interpolated)); + DEBUG ("latency_counter_get_percentile: latency_interpolated = %.3f", + CDTIME_T_TO_DOUBLE (latency_interpolated)); + return (latency_interpolated); } /* }}} cdtime_t latency_counter_get_percentile */ /* vim: set sw=2 sts=2 et fdm=marker : */ -- 2.30.2