Dmitri Plotnikov | 5effd85 | 2021-08-11 14:55:58 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2021 The Android Open Source Project |
| 3 | * Android BPF library - public API |
| 4 | * |
| 5 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 6 | * you may not use this file except in compliance with the License. |
| 7 | * You may obtain a copy of the License at |
| 8 | * |
| 9 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 10 | * |
| 11 | * Unless required by applicable law or agreed to in writing, software |
| 12 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 14 | * See the License for the specific language governing permissions and |
| 15 | * limitations under the License. |
| 16 | */ |
| 17 | |
| 18 | #pragma once |
| 19 | |
| 20 | #include <inttypes.h> |
| 21 | #include <log/log.h> |
| 22 | #include <time.h> |
| 23 | #include <sstream> |
| 24 | #include <string> |
| 25 | |
| 26 | /** |
| 27 | * An object that can track changes of some value over time, taking into account an additional |
| 28 | * dimension: the object's state. As the tracked value changes, the deltas are distributed |
| 29 | * among the object states in accordance with the time spent in those states. |
| 30 | */ |
| 31 | namespace android { |
| 32 | namespace battery { |
| 33 | |
| 34 | typedef uint16_t state_t; |
| 35 | |
| 36 | template <class T> |
| 37 | class MultiStateCounter { |
| 38 | uint16_t stateCount; |
| 39 | state_t currentState; |
| 40 | time_t lastStateChangeTimestamp; |
| 41 | T emptyValue; |
| 42 | T lastValue; |
| 43 | time_t lastUpdateTimestamp; |
| 44 | T deltaValue; |
| 45 | |
| 46 | struct State { |
| 47 | time_t timeInStateSinceUpdate; |
| 48 | T counter; |
| 49 | }; |
| 50 | |
| 51 | State* states; |
| 52 | |
| 53 | public: |
| 54 | MultiStateCounter(uint16_t stateCount, state_t initialState, const T& emptyValue, |
| 55 | time_t timestamp); |
| 56 | |
| 57 | virtual ~MultiStateCounter(); |
| 58 | |
| 59 | void setState(state_t state, time_t timestamp); |
| 60 | |
| 61 | void updateValue(const T& value, time_t timestamp); |
| 62 | |
| 63 | const T& getCount(state_t state); |
| 64 | |
| 65 | std::string toString(); |
| 66 | |
| 67 | private: |
| 68 | /** |
| 69 | * Subtracts previousValue from newValue and returns the result in outValue. |
| 70 | * Returns true iff the combination of previousValue and newValue is valid |
| 71 | * (newValue >= prevValue) |
| 72 | */ |
| 73 | bool delta(const T& previousValue, const T& newValue, T* outValue) const; |
| 74 | |
| 75 | /** |
| 76 | * Adds value2 to value1 and stores the result in value1. Denominator is |
| 77 | * guaranteed to be non-zero. |
| 78 | */ |
| 79 | void add(T* value1, const T& value2, const uint64_t numerator, |
| 80 | const uint64_t denominator) const; |
| 81 | |
| 82 | std::string valueToString(const T& value) const; |
| 83 | }; |
| 84 | |
| 85 | // ---------------------- MultiStateCounter Implementation ------------------------- |
| 86 | // Since MultiStateCounter is a template, the implementation must be inlined. |
| 87 | |
| 88 | template <class T> |
| 89 | MultiStateCounter<T>::MultiStateCounter(uint16_t stateCount, state_t initialState, |
| 90 | const T& emptyValue, time_t timestamp) |
| 91 | : stateCount(stateCount), |
| 92 | currentState(initialState), |
| 93 | lastStateChangeTimestamp(timestamp), |
| 94 | emptyValue(emptyValue), |
| 95 | lastValue(emptyValue), |
| 96 | lastUpdateTimestamp(timestamp), |
| 97 | deltaValue(emptyValue) { |
| 98 | states = new State[stateCount]; |
| 99 | for (int i = 0; i < stateCount; i++) { |
| 100 | states[i].timeInStateSinceUpdate = 0; |
| 101 | states[i].counter = emptyValue; |
| 102 | } |
| 103 | } |
| 104 | |
| 105 | template <class T> |
| 106 | MultiStateCounter<T>::~MultiStateCounter() { |
| 107 | delete[] states; |
| 108 | }; |
| 109 | |
| 110 | template <class T> |
| 111 | void MultiStateCounter<T>::setState(state_t state, time_t timestamp) { |
| 112 | if (timestamp >= lastStateChangeTimestamp) { |
| 113 | states[currentState].timeInStateSinceUpdate += timestamp - lastStateChangeTimestamp; |
| 114 | } else { |
| 115 | ALOGE("setState is called with an earlier timestamp: %lu, previous timestamp: %lu\n", |
| 116 | (unsigned long)timestamp, (unsigned long)lastStateChangeTimestamp); |
| 117 | // The accumulated durations have become unreliable. For example, if the timestamp |
| 118 | // sequence was 1000, 2000, 1000, 3000, if we accumulated the positive deltas, |
| 119 | // we would get 4000, which is greater than (last - first). This could lead to |
| 120 | // counts exceeding 100%. |
| 121 | for (int i = 0; i < stateCount; i++) { |
| 122 | states[i].timeInStateSinceUpdate = 0; |
| 123 | } |
| 124 | } |
| 125 | currentState = state; |
| 126 | lastStateChangeTimestamp = timestamp; |
| 127 | } |
| 128 | |
| 129 | template <class T> |
| 130 | void MultiStateCounter<T>::updateValue(const T& value, time_t timestamp) { |
| 131 | // Confirm the current state for the side-effect of updating the time-in-state |
| 132 | // counter for the current state. |
| 133 | setState(currentState, timestamp); |
| 134 | |
| 135 | if (timestamp > lastUpdateTimestamp) { |
| 136 | if (delta(lastValue, value, &deltaValue)) { |
| 137 | time_t timeSinceUpdate = timestamp - lastUpdateTimestamp; |
| 138 | for (int i = 0; i < stateCount; i++) { |
| 139 | time_t timeInState = states[i].timeInStateSinceUpdate; |
| 140 | if (timeInState) { |
| 141 | add(&states[i].counter, deltaValue, timeInState, timeSinceUpdate); |
| 142 | states[i].timeInStateSinceUpdate = 0; |
| 143 | } |
| 144 | } |
| 145 | } else { |
| 146 | std::stringstream str; |
| 147 | str << "updateValue is called with a value " << valueToString(value) |
| 148 | << ", which is lower than the previous value " << valueToString(lastValue) << "\n"; |
| 149 | ALOGE("%s", str.str().c_str()); |
| 150 | } |
| 151 | } else if (timestamp < lastUpdateTimestamp) { |
| 152 | ALOGE("updateValue is called with an earlier timestamp: %lu, previous timestamp: %lu\n", |
| 153 | (unsigned long)timestamp, (unsigned long)lastUpdateTimestamp); |
| 154 | } |
| 155 | lastValue = value; |
| 156 | lastUpdateTimestamp = timestamp; |
| 157 | } |
| 158 | |
| 159 | template <class T> |
| 160 | const T& MultiStateCounter<T>::getCount(state_t state) { |
| 161 | return states[state].counter; |
| 162 | } |
| 163 | |
| 164 | template <class T> |
| 165 | std::string MultiStateCounter<T>::toString() { |
| 166 | std::stringstream str; |
| 167 | str << "currentState: " << currentState |
| 168 | << " lastStateChangeTimestamp: " << lastStateChangeTimestamp |
| 169 | << " lastUpdateTimestamp: " << lastUpdateTimestamp << " states: ["; |
| 170 | for (int i = 0; i < stateCount; i++) { |
| 171 | if (i != 0) { |
| 172 | str << ", "; |
| 173 | } |
| 174 | str << i << ": time: " << states[i].timeInStateSinceUpdate |
| 175 | << " counter: " << valueToString(states[i].counter); |
| 176 | } |
| 177 | str << "]"; |
| 178 | return str.str(); |
| 179 | } |
| 180 | |
| 181 | } // namespace battery |
| 182 | } // namespace android |