1 /* 2 * Copyright (C) 2015 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 package com.android.internal.os; 17 18 import android.text.TextUtils; 19 import android.os.StrictMode; 20 import android.system.OsConstants; 21 import android.util.Slog; 22 23 import libcore.io.Libcore; 24 25 import java.io.BufferedReader; 26 import java.io.FileReader; 27 import java.io.IOException; 28 import java.util.Arrays; 29 30 /** 31 * Reads CPU time of a specific core spent at various frequencies and provides a delta from the 32 * last call to {@link #readDelta}. Each line in the proc file has the format: 33 * 34 * freq time 35 * 36 * where time is measured in jiffies. 37 */ 38 public class KernelCpuSpeedReader { 39 private static final String TAG = "KernelCpuSpeedReader"; 40 41 private final String mProcFile; 42 private final long[] mLastSpeedTimes; 43 private final long[] mDeltaSpeedTimes; 44 45 // How long a CPU jiffy is in milliseconds. 46 private final long mJiffyMillis; 47 48 /** 49 * @param cpuNumber The cpu (cpu0, cpu1, etc) whose state to read. 50 */ KernelCpuSpeedReader(int cpuNumber, int numSpeedSteps)51 public KernelCpuSpeedReader(int cpuNumber, int numSpeedSteps) { 52 mProcFile = String.format("/sys/devices/system/cpu/cpu%d/cpufreq/stats/time_in_state", 53 cpuNumber); 54 mLastSpeedTimes = new long[numSpeedSteps]; 55 mDeltaSpeedTimes = new long[numSpeedSteps]; 56 long jiffyHz = Libcore.os.sysconf(OsConstants._SC_CLK_TCK); 57 mJiffyMillis = 1000/jiffyHz; 58 } 59 60 /** 61 * The returned array is modified in subsequent calls to {@link #readDelta}. 62 * @return The time (in milliseconds) spent at different cpu speeds since the last call to 63 * {@link #readDelta}. 64 */ readDelta()65 public long[] readDelta() { 66 StrictMode.ThreadPolicy policy = StrictMode.allowThreadDiskReads(); 67 try (BufferedReader reader = new BufferedReader(new FileReader(mProcFile))) { 68 TextUtils.SimpleStringSplitter splitter = new TextUtils.SimpleStringSplitter(' '); 69 String line; 70 int speedIndex = 0; 71 while (speedIndex < mLastSpeedTimes.length && (line = reader.readLine()) != null) { 72 splitter.setString(line); 73 Long.parseLong(splitter.next()); 74 75 long time = Long.parseLong(splitter.next()) * mJiffyMillis; 76 if (time < mLastSpeedTimes[speedIndex]) { 77 // The stats reset when the cpu hotplugged. That means that the time 78 // we read is offset from 0, so the time is the delta. 79 mDeltaSpeedTimes[speedIndex] = time; 80 } else { 81 mDeltaSpeedTimes[speedIndex] = time - mLastSpeedTimes[speedIndex]; 82 } 83 mLastSpeedTimes[speedIndex] = time; 84 speedIndex++; 85 } 86 } catch (IOException e) { 87 Slog.e(TAG, "Failed to read cpu-freq: " + e.getMessage()); 88 Arrays.fill(mDeltaSpeedTimes, 0); 89 } finally { 90 StrictMode.setThreadPolicy(policy); 91 } 92 return mDeltaSpeedTimes; 93 } 94 } 95