chromium/components/system_cpu/cpu_probe.h

// 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.

#ifndef COMPONENTS_SYSTEM_CPU_CPU_PROBE_H_
#define COMPONENTS_SYSTEM_CPU_CPU_PROBE_H_

#include <memory>
#include <optional>

#include "base/functional/callback_forward.h"
#include "base/functional/callback_helpers.h"
#include "base/memory/weak_ptr.h"
#include "base/sequence_checker.h"
#include "base/thread_annotations.h"
#include "components/system_cpu/cpu_sample.h"

namespace system_cpu {

// Interface for retrieving the CPU load from the underlying OS on request.
//
// Operating systems differ in how they summarize the info needed to derive the
// compute pressure state. For example, the Linux kernel exposes CPU utilization
// as a summary over the device's entire uptime, while the Windows WMI exposes
// CPU utilization over the last second.
//
// This interface abstracts over the differences with a unified model where the
// implementation is responsible for integrating over the time between two
// Update() calls.
//
// Callers must call StartSampling() to establish a baseline. After this they
// can call RequestUpdate(), generally on a fixed schedule. Each call returns
// the total CPU usage of processors since the baseline or the last
// RequestUpdate() call.
//
// Instances are not thread-safe and should be used on the same sequence.
class CpuProbe { … };

}  // namespace system_cpu

#endif  // COMPONENTS_SYSTEM_CPU_CPU_PROBE_H_