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// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef UI_LATENCY_LATENCY_TRACKER_H_
#define UI_LATENCY_LATENCY_TRACKER_H_
#include "base/macros.h"
#include "services/metrics/public/cpp/ukm_source_id.h"
#include "ui/latency/latency_info.h"
namespace ui {
// Utility class for tracking the latency of events. Relies on LatencyInfo
// components logged by content::RenderWidgetHostLatencyTracker.
class LatencyTracker {
public:
explicit LatencyTracker(bool metric_sampling,
ukm::SourceId ukm_source_id = ukm::kInvalidSourceId);
~LatencyTracker() = default;
void OnEventStart(LatencyInfo* latency);
// Terminates latency tracking for events that triggered rendering, also
// performing relevant UMA latency reporting.
// Called when GPU buffers swap completes.
void OnGpuSwapBuffersCompleted(const LatencyInfo& latency);
protected:
ukm::SourceId ukm_source_id() const { return ukm_source_id_; }
private:
enum class InputMetricEvent {
SCROLL_BEGIN_TOUCH = 0,
SCROLL_UPDATE_TOUCH,
SCROLL_BEGIN_WHEEL,
SCROLL_UPDATE_WHEEL,
INPUT_METRIC_EVENT_MAX = SCROLL_UPDATE_WHEEL
};
void ReportUkmScrollLatency(
const InputMetricEvent& metric_event,
const LatencyInfo::LatencyComponent& start_component,
const LatencyInfo::LatencyComponent&
time_to_scroll_update_swap_begin_component,
const LatencyInfo::LatencyComponent& time_to_handled_component,
bool is_main_thread,
const ukm::SourceId ukm_source_id);
void ComputeEndToEndLatencyHistograms(
const LatencyInfo::LatencyComponent& gpu_swap_begin_component,
const LatencyInfo::LatencyComponent& gpu_swap_end_component,
const LatencyInfo& latency);
typedef struct SamplingScheme {
SamplingScheme() : interval_(1), last_sample_(0) {}
SamplingScheme(int interval)
: interval_(interval), last_sample_(rand() % interval) {}
bool ShouldReport() {
last_sample_++;
last_sample_ %= interval_;
return last_sample_ == 0;
}
private:
int interval_;
int last_sample_;
} SamplingScheme;
// Whether the sampling is needed for high volume metrics. This will be off
// when we are in unit tests. This is a temporary field so we can come up with
// a more permanent solution for crbug.com/739169.
bool metric_sampling_;
// The i'th member of this array stores the sampling rate for the i'th
// input metric event type. Initializing SamplingScheme with number X means
// that from every X events one will be reported. Note that the first event
// to report is also randomized.
SamplingScheme sampling_scheme_
[static_cast<int>(InputMetricEvent::INPUT_METRIC_EVENT_MAX) + 1] = {
SamplingScheme(5), // SCROLL_BEGIN_TOUCH
SamplingScheme(50), // SCROLL_UPDATE_TOUCH
SamplingScheme(5), // SCROLL_BEGIN_WHEEL
SamplingScheme(2), // SCROLL_UPDATE_WHEEL
};
const ukm::SourceId ukm_source_id_;
DISALLOW_COPY_AND_ASSIGN(LatencyTracker);
};
} // namespace latency
#endif // UI_LATENCY_LATENCY_TRACKER_H_
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