51e60305e6
To avoid the case where a single data point or too short window is used, causing bad behavior due to bad stats, update RateStatistics to return an Optional rather than a plain rate. There was also a strange off by one bug where the rate was slightly overestimated (N + 1 buckets, N ms time window). These changes requires updates to a number of places, and may very well cause seeming perf regressions (but the stats were probablty more wrong previously). BUG= R=mflodman@webrtc.org, stefan@webrtc.org Review URL: https://codereview.webrtc.org/2029593002 . Cr-Commit-Position: refs/heads/master@{#13103}
70 lines
2.1 KiB
C++
70 lines
2.1 KiB
C++
/*
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* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef WEBRTC_BASE_RATE_STATISTICS_H_
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#define WEBRTC_BASE_RATE_STATISTICS_H_
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#include <memory>
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#include "webrtc/base/optional.h"
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#include "webrtc/typedefs.h"
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namespace webrtc {
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class RateStatistics {
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public:
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// max_window_size_ms = Maximum window size in ms for the rate estimation.
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// Initial window size is set to this, but may be changed
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// to something lower by calling SetWindowSize().
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// scale = coefficient to convert counts/ms to desired units,
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// ex: if counts represents bytes, use 8*1000 to go to bits/s
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RateStatistics(int64_t max_window_size_ms, float scale);
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~RateStatistics();
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void Reset();
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void Update(size_t count, int64_t now_ms);
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rtc::Optional<uint32_t> Rate(int64_t now_ms);
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bool SetWindowSize(int64_t window_size_ms, int64_t now_ms);
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private:
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void EraseOld(int64_t now_ms);
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bool IsInitialized();
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// Counters are kept in buckets (circular buffer), with one bucket
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// per millisecond.
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struct Bucket {
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size_t sum; // Sum of all samples in this bucket.
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size_t samples; // Number of samples in this bucket.
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};
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std::unique_ptr<Bucket[]> buckets_;
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// Total count recorded in buckets.
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size_t accumulated_count_;
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// The total number of samples in the buckets.
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size_t num_samples_;
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// Oldest time recorded in buckets.
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int64_t oldest_time_;
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// Bucket index of oldest counter recorded in buckets.
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uint32_t oldest_index_;
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// To convert counts/ms to desired units
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const float scale_;
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// The window sizes, in ms, over which the rate is calculated.
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const int64_t max_window_size_ms_;
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int64_t current_window_size_ms_;
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};
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} // namespace webrtc
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#endif // WEBRTC_BASE_RATE_STATISTICS_H_
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