61abc85eb3
This patch adds a started counter, that is used to mark the number of operation that were started. This counter serves two purposes, it is a better indication for when to sample the data and it is used to indicate how many pending operations are. Signed-off-by: Amnon Heiman <amnon@scylladb.com>
114 lines
2.9 KiB
C++
114 lines
2.9 KiB
C++
/*
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* Copyright 2015 Cloudius Systems
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <boost/circular_buffer.hpp>
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#include "latency.hh"
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namespace utils {
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class ihistogram {
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public:
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// count holds all the events
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int64_t count;
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// total holds only the events we sample
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int64_t total;
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int64_t min;
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int64_t max;
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int64_t sum;
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int64_t started;
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double mean;
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double variance;
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int64_t sample_mask;
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boost::circular_buffer<int64_t> sample;
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ihistogram(size_t size = 1024, int64_t _sample_mask = 0x80)
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: count(0), total(0), min(0), max(0), sum(0), started(0), mean(0), variance(0),
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sample_mask(_sample_mask), sample(
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size) {
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}
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void mark(int64_t value) {
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if (total == 0 || value < min) {
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min = value;
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}
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if (total == 0 || value > max) {
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max = value;
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}
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if (total == 0) {
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mean = value;
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variance = 0;
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} else {
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double old_m = mean;
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double old_s = variance;
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mean = ((double)(sum + value)) / (total + 1);
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variance = old_s + ((value - old_m) * (value - mean));
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}
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sum += value;
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total++;
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count++;
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sample.push_back(value);
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}
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void mark(latency_counter& lc) {
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if (lc.is_start()) {
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mark(lc.stop().latency_in_nano());
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} else {
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count++;
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}
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}
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/**
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* Return true if the current event should be sample.
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* In the typical case, there is no need to use this method
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* Call set_latency, that would start a latency object if needed.
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*/
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bool should_sample() const {
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return total == 0 || (started & sample_mask);
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}
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/**
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* Set the latency according to the sample rate.
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*/
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ihistogram& set_latency(latency_counter& lc) {
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if (should_sample()) {
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lc.start();
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}
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started++;
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return *this;
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}
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/**
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* Allow to use the histogram as a counter
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* Increment the total number of events without
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* sampling the value.
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*/
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ihistogram& inc() {
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count++;
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return *this;
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}
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int64_t pending() const {
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return started - count;
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}
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};
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}
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