Mike Ma | 2ab0144 | 2018-02-13 14:22:47 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2018 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package com.android.internal.os; |
| 18 | |
| 19 | import android.os.StrictMode; |
| 20 | import android.os.SystemClock; |
| 21 | import android.util.Slog; |
| 22 | |
| 23 | import com.android.internal.annotations.VisibleForTesting; |
| 24 | |
Mike Ma | 363ccf7 | 2018-03-01 14:50:02 -0800 | [diff] [blame] | 25 | import java.io.FileNotFoundException; |
Mike Ma | 2ab0144 | 2018-02-13 14:22:47 -0800 | [diff] [blame] | 26 | import java.io.IOException; |
| 27 | import java.nio.ByteBuffer; |
| 28 | import java.nio.ByteOrder; |
| 29 | import java.nio.channels.FileChannel; |
Mike Ma | 363ccf7 | 2018-03-01 14:50:02 -0800 | [diff] [blame] | 30 | import java.nio.file.NoSuchFileException; |
Mike Ma | 2ab0144 | 2018-02-13 14:22:47 -0800 | [diff] [blame] | 31 | import java.nio.file.Path; |
| 32 | import java.nio.file.Paths; |
| 33 | import java.nio.file.StandardOpenOption; |
| 34 | |
| 35 | /** |
| 36 | * Reads cpu time proc files with throttling (adjustable interval). |
| 37 | * |
| 38 | * KernelCpuProcReader is implemented as singletons for built-in kernel proc files. Get___Instance() |
| 39 | * method will return corresponding reader instance. In order to prevent frequent GC, |
| 40 | * KernelCpuProcReader reuses a {@link ByteBuffer} to store data read from proc files. |
| 41 | * |
| 42 | * A KernelCpuProcReader instance keeps an error counter. When the number of read errors within that |
| 43 | * instance accumulates to 5, this instance will reject all further read requests. |
| 44 | * |
| 45 | * Each KernelCpuProcReader instance also has a throttler. Throttle interval can be adjusted via |
| 46 | * {@link #setThrottleInterval(long)} method. Default throttle interval is 3000ms. If current |
| 47 | * timestamp based on {@link SystemClock#elapsedRealtime()} is less than throttle interval from |
| 48 | * the last read timestamp, {@link #readBytes()} will return previous result. |
| 49 | * |
| 50 | * A KernelCpuProcReader instance is thread-unsafe. Caller needs to hold a lock on this object while |
| 51 | * accessing its instance methods or digesting the return values. |
| 52 | */ |
| 53 | public class KernelCpuProcReader { |
| 54 | private static final String TAG = "KernelCpuProcReader"; |
| 55 | private static final int ERROR_THRESHOLD = 5; |
| 56 | // Throttle interval in milliseconds |
| 57 | private static final long DEFAULT_THROTTLE_INTERVAL = 3000L; |
| 58 | private static final int INITIAL_BUFFER_SIZE = 8 * 1024; |
| 59 | private static final int MAX_BUFFER_SIZE = 1024 * 1024; |
| 60 | private static final String PROC_UID_FREQ_TIME = "/proc/uid_cpupower/time_in_state"; |
| 61 | private static final String PROC_UID_ACTIVE_TIME = "/proc/uid_cpupower/concurrent_active_time"; |
| 62 | private static final String PROC_UID_CLUSTER_TIME = "/proc/uid_cpupower/concurrent_policy_time"; |
| 63 | |
| 64 | private static final KernelCpuProcReader mFreqTimeReader = new KernelCpuProcReader( |
| 65 | PROC_UID_FREQ_TIME); |
| 66 | private static final KernelCpuProcReader mActiveTimeReader = new KernelCpuProcReader( |
| 67 | PROC_UID_ACTIVE_TIME); |
| 68 | private static final KernelCpuProcReader mClusterTimeReader = new KernelCpuProcReader( |
| 69 | PROC_UID_CLUSTER_TIME); |
| 70 | |
| 71 | public static KernelCpuProcReader getFreqTimeReaderInstance() { |
| 72 | return mFreqTimeReader; |
| 73 | } |
| 74 | |
| 75 | public static KernelCpuProcReader getActiveTimeReaderInstance() { |
| 76 | return mActiveTimeReader; |
| 77 | } |
| 78 | |
| 79 | public static KernelCpuProcReader getClusterTimeReaderInstance() { |
| 80 | return mClusterTimeReader; |
| 81 | } |
| 82 | |
| 83 | private int mErrors; |
| 84 | private long mThrottleInterval = DEFAULT_THROTTLE_INTERVAL; |
| 85 | private long mLastReadTime = Long.MIN_VALUE; |
| 86 | private final Path mProc; |
| 87 | private ByteBuffer mBuffer; |
| 88 | |
| 89 | @VisibleForTesting |
| 90 | public KernelCpuProcReader(String procFile) { |
| 91 | mProc = Paths.get(procFile); |
| 92 | mBuffer = ByteBuffer.allocateDirect(INITIAL_BUFFER_SIZE); |
| 93 | mBuffer.clear(); |
| 94 | } |
| 95 | |
| 96 | /** |
| 97 | * Reads all bytes from the corresponding proc file. |
| 98 | * |
| 99 | * If elapsed time since last call to this method is less than the throttle interval, it will |
| 100 | * return previous result. When IOException accumulates to 5, it will always return null. This |
| 101 | * method is thread-unsafe, so is the return value. Caller needs to hold a lock on this |
| 102 | * object while calling this method and digesting its return value. |
| 103 | * |
| 104 | * @return a {@link ByteBuffer} containing all bytes from the proc file. |
| 105 | */ |
| 106 | public ByteBuffer readBytes() { |
| 107 | if (mErrors >= ERROR_THRESHOLD) { |
| 108 | return null; |
| 109 | } |
| 110 | if (SystemClock.elapsedRealtime() < mLastReadTime + mThrottleInterval) { |
| 111 | if (mBuffer.limit() > 0 && mBuffer.limit() < mBuffer.capacity()) { |
| 112 | // mBuffer has data. |
| 113 | return mBuffer.asReadOnlyBuffer().order(ByteOrder.nativeOrder()); |
| 114 | } |
| 115 | return null; |
| 116 | } |
| 117 | mLastReadTime = SystemClock.elapsedRealtime(); |
| 118 | mBuffer.clear(); |
| 119 | final int oldMask = StrictMode.allowThreadDiskReadsMask(); |
| 120 | try (FileChannel fc = FileChannel.open(mProc, StandardOpenOption.READ)) { |
| 121 | while (fc.read(mBuffer) == mBuffer.capacity()) { |
| 122 | if (!resize()) { |
| 123 | mErrors++; |
| 124 | Slog.e(TAG, "Proc file is too large: " + mProc); |
| 125 | return null; |
| 126 | } |
| 127 | fc.position(0); |
| 128 | } |
Mike Ma | 363ccf7 | 2018-03-01 14:50:02 -0800 | [diff] [blame] | 129 | } catch (NoSuchFileException | FileNotFoundException e) { |
| 130 | // Happens when the kernel does not provide this file. Not a big issue. Just log it. |
| 131 | mErrors++; |
| 132 | Slog.w(TAG, "File not exist: " + mProc); |
| 133 | return null; |
Mike Ma | 2ab0144 | 2018-02-13 14:22:47 -0800 | [diff] [blame] | 134 | } catch (IOException e) { |
| 135 | mErrors++; |
| 136 | Slog.e(TAG, "Error reading: " + mProc, e); |
| 137 | return null; |
| 138 | } finally { |
| 139 | StrictMode.setThreadPolicyMask(oldMask); |
| 140 | } |
| 141 | mBuffer.flip(); |
| 142 | return mBuffer.asReadOnlyBuffer().order(ByteOrder.nativeOrder()); |
| 143 | } |
| 144 | |
| 145 | /** |
| 146 | * Sets the throttle interval. Set to 0 will disable throttling. Thread-unsafe, holding a lock |
| 147 | * on this object is recommended. |
| 148 | * |
| 149 | * @param throttleInterval throttle interval in milliseconds |
| 150 | */ |
| 151 | public void setThrottleInterval(long throttleInterval) { |
| 152 | if (throttleInterval >= 0) { |
| 153 | mThrottleInterval = throttleInterval; |
| 154 | } |
| 155 | } |
| 156 | |
| 157 | private boolean resize() { |
| 158 | if (mBuffer.capacity() >= MAX_BUFFER_SIZE) { |
| 159 | return false; |
| 160 | } |
| 161 | int newSize = Math.min(mBuffer.capacity() << 1, MAX_BUFFER_SIZE); |
| 162 | // Slog.i(TAG, "Resize buffer " + mBuffer.capacity() + " => " + newSize); |
| 163 | mBuffer = ByteBuffer.allocateDirect(newSize); |
| 164 | return true; |
| 165 | } |
| 166 | } |