/* * Copyright 2015 The WebRTC Project Authors. All rights reserved. * * Use of this source code is governed by a BSD-style license * that can be found in the LICENSE file in the root of the source * tree. An additional intellectual property rights grant can be found * in the file PATENTS. All contributing project authors may * be found in the AUTHORS file in the root of the source tree. */ package org.appspot.apprtc; import android.annotation.TargetApi; import android.content.Context; import android.content.Intent; import android.content.IntentFilter; import android.os.BatteryManager; import android.os.Build; import android.os.SystemClock; import android.util.Log; import androidx.annotation.Nullable; import java.io.BufferedReader; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStreamReader; import java.nio.charset.Charset; import java.util.Arrays; import java.util.Scanner; import java.util.concurrent.Executors; import java.util.concurrent.Future; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit; /** * Simple CPU monitor. The caller creates a CpuMonitor object which can then * be used via sampleCpuUtilization() to collect the percentual use of the * cumulative CPU capacity for all CPUs running at their nominal frequency. 3 * values are generated: (1) getCpuCurrent() returns the use since the last * sampleCpuUtilization(), (2) getCpuAvg3() returns the use since 3 prior * calls, and (3) getCpuAvgAll() returns the use over all SAMPLE_SAVE_NUMBER * calls. * *
CPUs in Android are often "offline", and while this of course means 0 Hz * as current frequency, in this state we cannot even get their nominal * frequency. We therefore tread carefully, and allow any CPU to be missing. * Missing CPUs are assumed to have the same nominal frequency as any close * lower-numbered CPU, but as soon as it is online, we'll get their proper * frequency and remember it. (Since CPU 0 in practice always seem to be * online, this unidirectional frequency inheritance should be no problem in * practice.) * *
Caveats: * o No provision made for zany "turbo" mode, common in the x86 world. * o No provision made for ARM big.LITTLE; if CPU n can switch behind our * back, we might get incorrect estimates. * o This is not thread-safe. To call asynchronously, create different * CpuMonitor objects. * *
If we can gather enough info to generate a sensible result, * sampleCpuUtilization returns true. It is designed to never throw an * exception. * *
sampleCpuUtilization should not be called too often in its present form,
* since then deltas would be small and the percent values would fluctuate and
* be unreadable. If it is desirable to call it more often than say once per
* second, one would need to increase SAMPLE_SAVE_NUMBER and probably use
* Queue Known problems:
* 1. Nexus 7 devices running Kitkat have a kernel which often output an
* incorrect 'idle' field in /proc/stat. The value is close to twice the
* correct value, and then returns to back to correct reading. Both when
* jumping up and back down we might create faulty CPU load readings.
*/
class CpuMonitor {
private static final String TAG = "CpuMonitor";
private static final int MOVING_AVERAGE_SAMPLES = 5;
private static final int CPU_STAT_SAMPLE_PERIOD_MS = 2000;
private static final int CPU_STAT_LOG_PERIOD_MS = 6000;
private final Context appContext;
// User CPU usage at current frequency.
private final MovingAverage userCpuUsage;
// System CPU usage at current frequency.
private final MovingAverage systemCpuUsage;
// Total CPU usage relative to maximum frequency.
private final MovingAverage totalCpuUsage;
// CPU frequency in percentage from maximum.
private final MovingAverage frequencyScale;
@Nullable
private ScheduledExecutorService executor;
private long lastStatLogTimeMs;
private long[] cpuFreqMax;
private int cpusPresent;
private int actualCpusPresent;
private boolean initialized;
private boolean cpuOveruse;
private String[] maxPath;
private String[] curPath;
private double[] curFreqScales;
@Nullable
private ProcStat lastProcStat;
private static class ProcStat {
final long userTime;
final long systemTime;
final long idleTime;
ProcStat(long userTime, long systemTime, long idleTime) {
this.userTime = userTime;
this.systemTime = systemTime;
this.idleTime = idleTime;
}
}
private static class MovingAverage {
private final int size;
private double sum;
private double currentValue;
private double[] circBuffer;
private int circBufferIndex;
public MovingAverage(int size) {
if (size <= 0) {
throw new AssertionError("Size value in MovingAverage ctor should be positive.");
}
this.size = size;
circBuffer = new double[size];
}
public void reset() {
Arrays.fill(circBuffer, 0);
circBufferIndex = 0;
sum = 0;
currentValue = 0;
}
public void addValue(double value) {
sum -= circBuffer[circBufferIndex];
circBuffer[circBufferIndex++] = value;
currentValue = value;
sum += value;
if (circBufferIndex >= size) {
circBufferIndex = 0;
}
}
public double getCurrent() {
return currentValue;
}
public double getAverage() {
return sum / (double) size;
}
}
public static boolean isSupported() {
return Build.VERSION.SDK_INT < Build.VERSION_CODES.N;
}
public CpuMonitor(Context context) {
if (!isSupported()) {
throw new RuntimeException("CpuMonitor is not supported on this Android version.");
}
Log.d(TAG, "CpuMonitor ctor.");
appContext = context.getApplicationContext();
userCpuUsage = new MovingAverage(MOVING_AVERAGE_SAMPLES);
systemCpuUsage = new MovingAverage(MOVING_AVERAGE_SAMPLES);
totalCpuUsage = new MovingAverage(MOVING_AVERAGE_SAMPLES);
frequencyScale = new MovingAverage(MOVING_AVERAGE_SAMPLES);
lastStatLogTimeMs = SystemClock.elapsedRealtime();
scheduleCpuUtilizationTask();
}
public void pause() {
if (executor != null) {
Log.d(TAG, "pause");
executor.shutdownNow();
executor = null;
}
}
public void resume() {
Log.d(TAG, "resume");
resetStat();
scheduleCpuUtilizationTask();
}
// TODO(bugs.webrtc.org/8491): Remove NoSynchronizedMethodCheck suppression.
@SuppressWarnings("NoSynchronizedMethodCheck")
public synchronized void reset() {
if (executor != null) {
Log.d(TAG, "reset");
resetStat();
cpuOveruse = false;
}
}
// TODO(bugs.webrtc.org/8491): Remove NoSynchronizedMethodCheck suppression.
@SuppressWarnings("NoSynchronizedMethodCheck")
public synchronized int getCpuUsageCurrent() {
return doubleToPercent(userCpuUsage.getCurrent() + systemCpuUsage.getCurrent());
}
// TODO(bugs.webrtc.org/8491): Remove NoSynchronizedMethodCheck suppression.
@SuppressWarnings("NoSynchronizedMethodCheck")
public synchronized int getCpuUsageAverage() {
return doubleToPercent(userCpuUsage.getAverage() + systemCpuUsage.getAverage());
}
// TODO(bugs.webrtc.org/8491): Remove NoSynchronizedMethodCheck suppression.
@SuppressWarnings("NoSynchronizedMethodCheck")
public synchronized int getFrequencyScaleAverage() {
return doubleToPercent(frequencyScale.getAverage());
}
private void scheduleCpuUtilizationTask() {
if (executor != null) {
executor.shutdownNow();
executor = null;
}
executor = Executors.newSingleThreadScheduledExecutor();
@SuppressWarnings("unused") // Prevent downstream linter warnings.
Future> possiblyIgnoredError = executor.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
cpuUtilizationTask();
}
}, 0, CPU_STAT_SAMPLE_PERIOD_MS, TimeUnit.MILLISECONDS);
}
private void cpuUtilizationTask() {
boolean cpuMonitorAvailable = sampleCpuUtilization();
if (cpuMonitorAvailable
&& SystemClock.elapsedRealtime() - lastStatLogTimeMs >= CPU_STAT_LOG_PERIOD_MS) {
lastStatLogTimeMs = SystemClock.elapsedRealtime();
String statString = getStatString();
Log.d(TAG, statString);
}
}
private void init() {
try (FileInputStream fin = new FileInputStream("/sys/devices/system/cpu/present");
InputStreamReader streamReader = new InputStreamReader(fin, Charset.forName("UTF-8"));
BufferedReader reader = new BufferedReader(streamReader);
Scanner scanner = new Scanner(reader).useDelimiter("[-\n]");) {
scanner.nextInt(); // Skip leading number 0.
cpusPresent = 1 + scanner.nextInt();
scanner.close();
} catch (FileNotFoundException e) {
Log.e(TAG, "Cannot do CPU stats since /sys/devices/system/cpu/present is missing");
} catch (IOException e) {
Log.e(TAG, "Error closing file");
} catch (Exception e) {
Log.e(TAG, "Cannot do CPU stats due to /sys/devices/system/cpu/present parsing problem");
}
cpuFreqMax = new long[cpusPresent];
maxPath = new String[cpusPresent];
curPath = new String[cpusPresent];
curFreqScales = new double[cpusPresent];
for (int i = 0; i < cpusPresent; i++) {
cpuFreqMax[i] = 0; // Frequency "not yet determined".
curFreqScales[i] = 0;
maxPath[i] = "/sys/devices/system/cpu/cpu" + i + "/cpufreq/cpuinfo_max_freq";
curPath[i] = "/sys/devices/system/cpu/cpu" + i + "/cpufreq/scaling_cur_freq";
}
lastProcStat = new ProcStat(0, 0, 0);
resetStat();
initialized = true;
}
private synchronized void resetStat() {
userCpuUsage.reset();
systemCpuUsage.reset();
totalCpuUsage.reset();
frequencyScale.reset();
lastStatLogTimeMs = SystemClock.elapsedRealtime();
}
private int getBatteryLevel() {
// Use sticky broadcast with null receiver to read battery level once only.
Intent intent = appContext.registerReceiver(
null /* receiver */, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
int batteryLevel = 0;
int batteryScale = intent.getIntExtra(BatteryManager.EXTRA_SCALE, 100);
if (batteryScale > 0) {
batteryLevel =
(int) (100f * intent.getIntExtra(BatteryManager.EXTRA_LEVEL, 0) / batteryScale);
}
return batteryLevel;
}
/**
* Re-measure CPU use. Call this method at an interval of around 1/s.
* This method returns true on success. The fields
* cpuCurrent, cpuAvg3, and cpuAvgAll are updated on success, and represents:
* cpuCurrent: The CPU use since the last sampleCpuUtilization call.
* cpuAvg3: The average CPU over the last 3 calls.
* cpuAvgAll: The average CPU over the last SAMPLE_SAVE_NUMBER calls.
*/
private synchronized boolean sampleCpuUtilization() {
long lastSeenMaxFreq = 0;
long cpuFreqCurSum = 0;
long cpuFreqMaxSum = 0;
if (!initialized) {
init();
}
if (cpusPresent == 0) {
return false;
}
actualCpusPresent = 0;
for (int i = 0; i < cpusPresent; i++) {
/*
* For each CPU, attempt to first read its max frequency, then its
* current frequency. Once as the max frequency for a CPU is found,
* save it in cpuFreqMax[].
*/
curFreqScales[i] = 0;
if (cpuFreqMax[i] == 0) {
// We have never found this CPU's max frequency. Attempt to read it.
long cpufreqMax = readFreqFromFile(maxPath[i]);
if (cpufreqMax > 0) {
Log.d(TAG, "Core " + i + ". Max frequency: " + cpufreqMax);
lastSeenMaxFreq = cpufreqMax;
cpuFreqMax[i] = cpufreqMax;
maxPath[i] = null; // Kill path to free its memory.
}
} else {
lastSeenMaxFreq = cpuFreqMax[i]; // A valid, previously read value.
}
long cpuFreqCur = readFreqFromFile(curPath[i]);
if (cpuFreqCur == 0 && lastSeenMaxFreq == 0) {
// No current frequency information for this CPU core - ignore it.
continue;
}
if (cpuFreqCur > 0) {
actualCpusPresent++;
}
cpuFreqCurSum += cpuFreqCur;
/* Here, lastSeenMaxFreq might come from
* 1. cpuFreq[i], or
* 2. a previous iteration, or
* 3. a newly read value, or
* 4. hypothetically from the pre-loop dummy.
*/
cpuFreqMaxSum += lastSeenMaxFreq;
if (lastSeenMaxFreq > 0) {
curFreqScales[i] = (double) cpuFreqCur / lastSeenMaxFreq;
}
}
if (cpuFreqCurSum == 0 || cpuFreqMaxSum == 0) {
Log.e(TAG, "Could not read max or current frequency for any CPU");
return false;
}
/*
* Since the cycle counts are for the period between the last invocation
* and this present one, we average the percentual CPU frequencies between
* now and the beginning of the measurement period. This is significantly
* incorrect only if the frequencies have peeked or dropped in between the
* invocations.
*/
double currentFrequencyScale = cpuFreqCurSum / (double) cpuFreqMaxSum;
if (frequencyScale.getCurrent() > 0) {
currentFrequencyScale = (frequencyScale.getCurrent() + currentFrequencyScale) * 0.5;
}
ProcStat procStat = readProcStat();
if (procStat == null) {
return false;
}
long diffUserTime = procStat.userTime - lastProcStat.userTime;
long diffSystemTime = procStat.systemTime - lastProcStat.systemTime;
long diffIdleTime = procStat.idleTime - lastProcStat.idleTime;
long allTime = diffUserTime + diffSystemTime + diffIdleTime;
if (currentFrequencyScale == 0 || allTime == 0) {
return false;
}
// Update statistics.
frequencyScale.addValue(currentFrequencyScale);
double currentUserCpuUsage = diffUserTime / (double) allTime;
userCpuUsage.addValue(currentUserCpuUsage);
double currentSystemCpuUsage = diffSystemTime / (double) allTime;
systemCpuUsage.addValue(currentSystemCpuUsage);
double currentTotalCpuUsage =
(currentUserCpuUsage + currentSystemCpuUsage) * currentFrequencyScale;
totalCpuUsage.addValue(currentTotalCpuUsage);
// Save new measurements for next round's deltas.
lastProcStat = procStat;
return true;
}
private int doubleToPercent(double d) {
return (int) (d * 100 + 0.5);
}
private synchronized String getStatString() {
StringBuilder stat = new StringBuilder();
stat.append("CPU User: ")
.append(doubleToPercent(userCpuUsage.getCurrent()))
.append("/")
.append(doubleToPercent(userCpuUsage.getAverage()))
.append(". System: ")
.append(doubleToPercent(systemCpuUsage.getCurrent()))
.append("/")
.append(doubleToPercent(systemCpuUsage.getAverage()))
.append(". Freq: ")
.append(doubleToPercent(frequencyScale.getCurrent()))
.append("/")
.append(doubleToPercent(frequencyScale.getAverage()))
.append(". Total usage: ")
.append(doubleToPercent(totalCpuUsage.getCurrent()))
.append("/")
.append(doubleToPercent(totalCpuUsage.getAverage()))
.append(". Cores: ")
.append(actualCpusPresent);
stat.append("( ");
for (int i = 0; i < cpusPresent; i++) {
stat.append(doubleToPercent(curFreqScales[i])).append(" ");
}
stat.append("). Battery: ").append(getBatteryLevel());
if (cpuOveruse) {
stat.append(". Overuse.");
}
return stat.toString();
}
/**
* Read a single integer value from the named file. Return the read value
* or if an error occurs return 0.
*/
private long readFreqFromFile(String fileName) {
long number = 0;
try (FileInputStream stream = new FileInputStream(fileName);
InputStreamReader streamReader = new InputStreamReader(stream, Charset.forName("UTF-8"));
BufferedReader reader = new BufferedReader(streamReader)) {
String line = reader.readLine();
number = parseLong(line);
} catch (FileNotFoundException e) {
// CPU core is off, so file with its scaling frequency .../cpufreq/scaling_cur_freq
// is not present. This is not an error.
} catch (IOException e) {
// CPU core is off, so file with its scaling frequency .../cpufreq/scaling_cur_freq
// is empty. This is not an error.
}
return number;
}
private static long parseLong(String value) {
long number = 0;
try {
number = Long.parseLong(value);
} catch (NumberFormatException e) {
Log.e(TAG, "parseLong error.", e);
}
return number;
}
/*
* Read the current utilization of all CPUs using the cumulative first line
* of /proc/stat.
*/
@SuppressWarnings("StringSplitter")
private @Nullable ProcStat readProcStat() {
long userTime = 0;
long systemTime = 0;
long idleTime = 0;
try (FileInputStream stream = new FileInputStream("/proc/stat");
InputStreamReader streamReader = new InputStreamReader(stream, Charset.forName("UTF-8"));
BufferedReader reader = new BufferedReader(streamReader)) {
// line should contain something like this:
// cpu 5093818 271838 3512830 165934119 101374 447076 272086 0 0 0
// user nice system idle iowait irq softirq
String line = reader.readLine();
String[] lines = line.split("\\s+");
int length = lines.length;
if (length >= 5) {
userTime = parseLong(lines[1]); // user
userTime += parseLong(lines[2]); // nice
systemTime = parseLong(lines[3]); // system
idleTime = parseLong(lines[4]); // idle
}
if (length >= 8) {
userTime += parseLong(lines[5]); // iowait
systemTime += parseLong(lines[6]); // irq
systemTime += parseLong(lines[7]); // softirq
}
} catch (FileNotFoundException e) {
Log.e(TAG, "Cannot open /proc/stat for reading", e);
return null;
} catch (Exception e) {
Log.e(TAG, "Problems parsing /proc/stat", e);
return null;
}
return new ProcStat(userTime, systemTime, idleTime);
}
}