chromium/chrome/browser/metrics/power/process_metrics_recorder_util.cc

// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "chrome/browser/metrics/power/process_metrics_recorder_util.h"

#include <cmath>
#include <optional>

#include "base/metrics/histogram_functions.h"
#include "base/strings/strcat.h"
#include "base/time/time.h"
#include "build/build_config.h"

namespace {

// CPU usage metrics are provided as a double in the [0.0, number of cores *
// 100.0] range. The CPU usage is usually below 1%, so the histograms are
// reported with a 1/10000 granularity to make analyzing the data easier
// (otherwise almost all samples end up in the same [0, 1[ bucket).
constexpr int kCPUUsageFactor = …;
// We scale up to the equivalent of 2 CPU cores fully loaded. More than this
// doesn't really matter, as we're already in a terrible place. This used to
// be capped at 64 cores but the data showed that this was way too much, the
// per process CPU usage really rarely exceeds 100% of one core.
constexpr int kCPUUsageHistogramMin = …;
constexpr int kCPUUsageHistogramMax = …;
constexpr int kCPUUsageHistogramBucketCount = …;

#if BUILDFLAG(IS_WIN)
bool HasConstantRateTSC() {
#if defined(ARCH_CPU_ARM64)
  // Constant rate TSC is never support on Arm CPUs.
  return false;
#else
  // Probe the CPU to detect if constant-rate TSC is supported.
  return base::time_internal::HasConstantRateTSC();
#endif
}
#endif  // BUILDFLAG(IS_WIN)

void RecordAverageCPUUsage(const char* histogram_suffix,
                           const std::optional<double>& cpu_usage) { … }

}  // namespace

void RecordProcessHistograms(const char* histogram_suffix,
                             const ProcessMonitor::Metrics& metrics) { … }