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239 lines
7.6 KiB
239 lines
7.6 KiB
/* |
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* |
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* Copyright 2015, Google Inc. |
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* All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions are |
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* met: |
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* |
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* * Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* * Redistributions in binary form must reproduce the above |
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* copyright notice, this list of conditions and the following disclaimer |
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* in the documentation and/or other materials provided with the |
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* distribution. |
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* * Neither the name of Google Inc. nor the names of its |
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* contributors may be used to endorse or promote products derived from |
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* this software without specific prior written permission. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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* |
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*/ |
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#include <grpc/support/histogram.h> |
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#include <math.h> |
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#include <stddef.h> |
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#include <string.h> |
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#include <grpc/support/alloc.h> |
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#include <grpc/support/port_platform.h> |
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#include <grpc/support/log.h> |
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#include <grpc/support/useful.h> |
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/* Histograms are stored with exponentially increasing bucket sizes. |
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The first bucket is [0, m) where m = 1 + resolution |
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Bucket n (n>=1) contains [m**n, m**(n+1)) |
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There are sufficient buckets to reach max_bucket_start */ |
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struct gpr_histogram { |
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/* Sum of all values seen so far */ |
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double sum; |
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/* Sum of squares of all values seen so far */ |
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double sum_of_squares; |
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/* number of values seen so far */ |
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double count; |
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/* m in the description */ |
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double multiplier; |
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double one_on_log_multiplier; |
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/* minimum value seen */ |
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double min_seen; |
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/* maximum value seen */ |
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double max_seen; |
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/* maximum representable value */ |
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double max_possible; |
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/* number of buckets */ |
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size_t num_buckets; |
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/* the buckets themselves */ |
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gpr_uint32 *buckets; |
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}; |
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/* determine a bucket index given a value - does no bounds checking */ |
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static size_t bucket_for_unchecked(gpr_histogram *h, double x) { |
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return (size_t)(log(x) * h->one_on_log_multiplier); |
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} |
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/* bounds checked version of the above */ |
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static size_t bucket_for(gpr_histogram *h, double x) { |
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size_t bucket = bucket_for_unchecked(h, GPR_CLAMP(x, 0, h->max_possible)); |
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GPR_ASSERT(bucket < h->num_buckets); |
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return bucket; |
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} |
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/* at what value does a bucket start? */ |
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static double bucket_start(gpr_histogram *h, double x) { |
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return pow(h->multiplier, x); |
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} |
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gpr_histogram *gpr_histogram_create(double resolution, |
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double max_bucket_start) { |
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gpr_histogram *h = gpr_malloc(sizeof(gpr_histogram)); |
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GPR_ASSERT(resolution > 0.0); |
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GPR_ASSERT(max_bucket_start > resolution); |
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h->sum = 0.0; |
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h->sum_of_squares = 0.0; |
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h->multiplier = 1.0 + resolution; |
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h->one_on_log_multiplier = 1.0 / log(1.0 + resolution); |
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h->max_possible = max_bucket_start; |
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h->count = 0.0; |
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h->min_seen = max_bucket_start; |
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h->max_seen = 0.0; |
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h->num_buckets = bucket_for_unchecked(h, max_bucket_start) + 1; |
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GPR_ASSERT(h->num_buckets > 1); |
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GPR_ASSERT(h->num_buckets < 100000000); |
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h->buckets = gpr_malloc(sizeof(gpr_uint32) * h->num_buckets); |
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memset(h->buckets, 0, sizeof(gpr_uint32) * h->num_buckets); |
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return h; |
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} |
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void gpr_histogram_destroy(gpr_histogram *h) { |
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gpr_free(h->buckets); |
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gpr_free(h); |
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} |
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void gpr_histogram_add(gpr_histogram *h, double x) { |
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h->sum += x; |
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h->sum_of_squares += x * x; |
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h->count++; |
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if (x < h->min_seen) { |
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h->min_seen = x; |
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} |
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if (x > h->max_seen) { |
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h->max_seen = x; |
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} |
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h->buckets[bucket_for(h, x)]++; |
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} |
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int gpr_histogram_merge(gpr_histogram *dst, gpr_histogram *src) { |
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if ((dst->num_buckets != src->num_buckets) || |
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(dst->multiplier != src->multiplier)) { |
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/* Fail because these histograms don't match */ |
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return 0; |
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} |
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gpr_histogram_merge_contents(dst, src->buckets, src->num_buckets, |
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src->min_seen, src->max_seen, src->sum, |
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src->sum_of_squares, src->count); |
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return 1; |
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} |
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void gpr_histogram_merge_contents(gpr_histogram *dst, const gpr_uint32 *data, |
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size_t data_count, double min_seen, |
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double max_seen, double sum, |
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double sum_of_squares, double count) { |
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size_t i; |
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GPR_ASSERT(dst->num_buckets == data_count); |
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dst->sum += sum; |
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dst->sum_of_squares += sum_of_squares; |
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dst->count += count; |
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if (min_seen < dst->min_seen) { |
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dst->min_seen = min_seen; |
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} |
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if (max_seen > dst->max_seen) { |
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dst->max_seen = max_seen; |
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} |
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for (i = 0; i < dst->num_buckets; i++) { |
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dst->buckets[i] += data[i]; |
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} |
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} |
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static double threshold_for_count_below(gpr_histogram *h, double count_below) { |
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double count_so_far; |
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double lower_bound; |
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double upper_bound; |
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size_t lower_idx; |
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size_t upper_idx; |
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GPR_ASSERT(h->count >= 1); |
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if (count_below <= 0) { |
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return h->min_seen; |
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} |
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if (count_below >= h->count) { |
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return h->max_seen; |
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} |
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/* find the lowest bucket that gets us above count_below */ |
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count_so_far = 0.0; |
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for (lower_idx = 0; lower_idx < h->num_buckets; lower_idx++) { |
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count_so_far += h->buckets[lower_idx]; |
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if (count_so_far >= count_below) { |
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break; |
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} |
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} |
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if (count_so_far == count_below) { |
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/* this bucket hits the threshold exactly... we should be midway through |
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any run of zero values following the bucket */ |
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for (upper_idx = lower_idx + 1; upper_idx < h->num_buckets; upper_idx++) { |
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if (h->buckets[upper_idx]) { |
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break; |
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} |
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} |
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return (bucket_start(h, lower_idx) + bucket_start(h, upper_idx)) / 2.0; |
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} else { |
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/* treat values as uniform throughout the bucket, and find where this value |
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should lie */ |
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lower_bound = bucket_start(h, lower_idx); |
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upper_bound = bucket_start(h, lower_idx + 1); |
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return GPR_CLAMP(upper_bound - (upper_bound - lower_bound) * |
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(count_so_far - count_below) / |
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h->buckets[lower_idx], |
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h->min_seen, h->max_seen); |
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} |
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} |
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double gpr_histogram_percentile(gpr_histogram *h, double percentile) { |
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return threshold_for_count_below(h, h->count * percentile / 100.0); |
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} |
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double gpr_histogram_mean(gpr_histogram *h) { |
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GPR_ASSERT(h->count); |
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return h->sum / h->count; |
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} |
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double gpr_histogram_stddev(gpr_histogram *h) { |
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return sqrt(gpr_histogram_variance(h)); |
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} |
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double gpr_histogram_variance(gpr_histogram *h) { |
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if (h->count == 0) return 0.0; |
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return (h->sum_of_squares * h->count - h->sum * h->sum) / |
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(h->count * h->count); |
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} |
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double gpr_histogram_maximum(gpr_histogram *h) { return h->max_seen; } |
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double gpr_histogram_minimum(gpr_histogram *h) { return h->min_seen; } |
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double gpr_histogram_count(gpr_histogram *h) { return h->count; } |
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double gpr_histogram_sum(gpr_histogram *h) { return h->sum; } |
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double gpr_histogram_sum_of_squares(gpr_histogram *h) { |
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return h->sum_of_squares; |
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} |
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const gpr_uint32 *gpr_histogram_get_contents(gpr_histogram *h, size_t *size) { |
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*size = h->num_buckets; |
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return h->buckets; |
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}
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