1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
|
// 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 {
public:
using SampleCallback = base::OnceCallback<void(std::optional<CpuSample>)>;
// Instantiates the CpuProbe subclass most suitable for the current platform.
//
// Returns nullptr if no suitable implementation exists.
static std::unique_ptr<CpuProbe> Create();
CpuProbe(const CpuProbe&) = delete;
CpuProbe& operator=(const CpuProbe&) = delete;
virtual ~CpuProbe();
// Samples the CPU load to get a baseline for calls to RequestSample(). May be
// called again to refresh the baseline.
// `started_callback` will be invoked once the baseline is available, so tests
// can verify the timing.
void StartSampling(base::OnceClosure started_callback = base::DoNothing());
// Invokes `callback` with the CPU load since the last call to
// RequestSample(). It's an error to call this without calling StartSampling()
// first.
void RequestSample(SampleCallback callback);
// Called to return a WeakPtr to the CpuProbe. Subclasses must own a
// WeakPtrFactory to implement this.
virtual base::WeakPtr<CpuProbe> GetWeakPtr() = 0;
protected:
// The constructor is intentionally only exposed to subclasses. Production
// code must use the Create() factory method.
CpuProbe();
// Implemented by subclasses to retrieve the CPU usage for different operating
// systems. It must call `callback` with the result.
virtual void Update(SampleCallback callback) = 0;
SEQUENCE_CHECKER(sequence_checker_);
private:
// Called with the result of an Update() triggered by StartSampling(). Will do
// some bookkeeping and then call `started_callback`, ignoring the
// CpuSample.
void OnSamplingStarted(base::OnceClosure started_callback,
std::optional<CpuSample>);
// Called with the result of an Update() triggered by RequestSample(). Will do
// some bookkeeping and then pass `sample` to `callback`.
void OnSampleAvailable(SampleCallback callback,
std::optional<CpuSample> sample);
// True if the CpuProbe state will be reported after the next update.
//
// The CpuSample reported by many CpuProbe implementations relies
// on the differences observed between two Update() calls. For this reason,
// the CpuSample reported after a first Update() call is not
// reported via the SampleCallback.
bool got_probe_baseline_ GUARDED_BY_CONTEXT(sequence_checker_) = false;
};
} // namespace system_cpu
#endif // COMPONENTS_SYSTEM_CPU_CPU_PROBE_H_
|
