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// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CHROME_BROWSER_ASH_ARC_TRACING_ARC_GRAPHICS_JANK_DETECTOR_H_
#define CHROME_BROWSER_ASH_ARC_TRACING_ARC_GRAPHICS_JANK_DETECTOR_H_
#include <vector>
#include "base/functional/callback.h"
#include "base/time/time.h"
namespace arc {
// Detector is used to determine janks in the sequence of periodic samples that
// have a timestamp. It conceptually has the following phases:
// * kWarmUp - at this stage, samples are ignored, assuming the app is just
// activated or resumed.
// * kRateDetection - at this stage, samples are collected to determine the
// prevailing or normal rate. Once enough samples are
// collected, rate is determined as 33% cut-off of sorted
// sample durations.
// * kActive - at this stage each new sample is tested against detected normal
// rate and in case timestamp offset of the sample is longer than
// 190% of the determined period than this is considered as a
// jank.
// In case the next sample appears after a long interval this is not considered
// as a jank and detector switches to warm-up stage.
// Detector may work in fixed mode, activated by |SetPeriodFixed| call. In this
// mode detector skips kWarmUp and kRateDetection and always watches for janks.
class ArcGraphicsJankDetector {
public:
using JankCallback = base::RepeatingCallback<void(base::Time timestamp)>;
enum class Stage {
kWarmUp, // ignore any update
kRateDetection, // detect the update rate
kActive, // looking for janks
};
// Number of samples to skip during the warm up.
static constexpr int kWarmUpSamples = 10;
// Number of samples to collect for the rate detection.
static constexpr size_t kSamplesForRateDetection = 15;
// Constant to detect pause to reduce the chance of triggering jank detection
// in case Android app just not producing the samples due to inactivity.
static constexpr base::TimeDelta kPauseDetectionThreshold =
base::Seconds(0.25);
explicit ArcGraphicsJankDetector(const JankCallback& callback);
ArcGraphicsJankDetector(const ArcGraphicsJankDetector&) = delete;
ArcGraphicsJankDetector& operator=(const ArcGraphicsJankDetector&) = delete;
~ArcGraphicsJankDetector();
// Returns whether there are enough samples to run detector.
static bool IsEnoughSamplesToDetect(size_t num_samples);
// Resets detector to its initial state, stage is set to |Stage::kWarmUp| with
// the initial number of warm up samples. Fixed period is discarded if it was
// set.
void Reset();
// Sets the expected refresh rate. This disables |Stage::kWarmUp| and
// |Stage::kRateDetection| stages and keeps detector in |Stage::kActive|
// stage.
void SetPeriodFixed(const base::TimeDelta& period);
// Notifies about the next sample with corresponding timestamp.
void OnSample(base::Time timestamp);
Stage stage() const { return stage_; }
base::TimeDelta period() const { return period_; }
private:
// Once jank is detected |callback_| is fired.
JankCallback callback_;
Stage stage_;
base::Time last_sample_time_;
int warm_up_sample_cnt_;
std::vector<base::TimeDelta> intervals_;
// Considered as normal period.
base::TimeDelta period_;
// Period fixed.
bool period_fixed_ = false;
};
} // namespace arc
#endif // CHROME_BROWSER_ASH_ARC_TRACING_ARC_GRAPHICS_JANK_DETECTOR_H_
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