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/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.internal.os;
import android.annotation.Nullable;
import android.os.Process;
import android.util.Slog;
import com.android.internal.annotations.VisibleForTesting;
import com.android.internal.util.ArrayUtils;
import com.android.internal.util.Preconditions;
import java.io.IOException;
import java.nio.file.DirectoryStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.function.Predicate;
/**
* Iterates over processes, and all threads owned by those processes, and return the CPU usage for
* each thread. The CPU usage statistics contain the amount of time spent in a frequency band. CPU
* usage is collected using {@link ProcTimeInStateReader}.
*
* We only collect CPU data for processes and threads that are owned by certain UIDs. These UIDs
* are configured via {@link #setUidPredicate}.
*
*
Frequencies are bucketed together to reduce the amount of data created. This means that we
* return less frequencies than provided by {@link ProcTimeInStateReader}. The number of frequencies
* is configurable by {@link #setNumBuckets}. Frequencies are reported as the lowest frequency in
* that range. Frequencies are spread as evenly as possible across the buckets. The buckets do not
* cross over the little/big frequencies reported.
*
*
N.B.: In order to bucket across little/big frequencies correctly, we assume that the {@code
* time_in_state} file contains every little core frequency in ascending order, followed by every
* big core frequency in ascending order. This assumption might not hold for devices with different
* kernel implementations of the {@code time_in_state} file generation.
*/
public class KernelCpuThreadReader {
private static final String TAG = "KernelCpuThreadReader";
private static final boolean DEBUG = false;
/**
* The name of the file to read CPU statistics from, must be found in {@code
* /proc/$PID/task/$TID}
*/
private static final String CPU_STATISTICS_FILENAME = "time_in_state";
/**
* The name of the file to read process command line invocation from, must be found in {@code
* /proc/$PID/}
*/
private static final String PROCESS_NAME_FILENAME = "cmdline";
/**
* The name of the file to read thread name from, must be found in {@code /proc/$PID/task/$TID}
*/
private static final String THREAD_NAME_FILENAME = "comm";
/** Glob pattern for the process directory names under {@code proc} */
private static final String PROCESS_DIRECTORY_FILTER = "[0-9]*";
/** Default process name when the name can't be read */
private static final String DEFAULT_PROCESS_NAME = "unknown_process";
/** Default thread name when the name can't be read */
private static final String DEFAULT_THREAD_NAME = "unknown_thread";
/** Default mount location of the {@code proc} filesystem */
private static final Path DEFAULT_PROC_PATH = Paths.get("/proc");
/** The initial {@code time_in_state} file for {@link ProcTimeInStateReader} */
private static final Path DEFAULT_INITIAL_TIME_IN_STATE_PATH =
DEFAULT_PROC_PATH.resolve("self/time_in_state");
/** Value returned when there was an error getting an integer ID value (e.g. PID, UID) */
private static final int ID_ERROR = -1;
/**
* When checking whether to report data for a thread, we check the UID of the thread's owner
* against this predicate
*/
private Predicate mUidPredicate;
/** Where the proc filesystem is mounted */
private final Path mProcPath;
/**
* Frequencies read from the {@code time_in_state} file. Read from {@link
* #mProcTimeInStateReader#getCpuFrequenciesKhz()} and cast to {@code int[]}
*/
private int[] mFrequenciesKhz;
/** Used to read and parse {@code time_in_state} files */
private final ProcTimeInStateReader mProcTimeInStateReader;
/** Used to sort frequencies and usage times into buckets */
private FrequencyBucketCreator mFrequencyBucketCreator;
private final Injector mInjector;
/**
* Create with a path where `proc` is mounted. Used primarily for testing
*
* @param procPath where `proc` is mounted (to find, see {@code mount | grep ^proc})
* @param initialTimeInStatePath where the initial {@code time_in_state} file exists to define
* format
*/
@VisibleForTesting
public KernelCpuThreadReader(
int numBuckets,
Predicate uidPredicate,
Path procPath,
Path initialTimeInStatePath,
Injector injector)
throws IOException {
mUidPredicate = uidPredicate;
mProcPath = procPath;
mProcTimeInStateReader = new ProcTimeInStateReader(initialTimeInStatePath);
mInjector = injector;
setNumBuckets(numBuckets);
}
/**
* Create the reader and handle exceptions during creation
*
* @return the reader, null if an exception was thrown during creation
*/
@Nullable
public static KernelCpuThreadReader create(int numBuckets, Predicate uidPredicate) {
try {
return new KernelCpuThreadReader(
numBuckets,
uidPredicate,
DEFAULT_PROC_PATH,
DEFAULT_INITIAL_TIME_IN_STATE_PATH,
new Injector());
} catch (IOException e) {
Slog.e(TAG, "Failed to initialize KernelCpuThreadReader", e);
return null;
}
}
/**
* Get the per-thread CPU usage of all processes belonging to a set of UIDs
*
* This function will crawl through all process {@code proc} directories found by the pattern
* {@code /proc/[0-9]*}, and then check the UID using {@code /proc/$PID/status}. This takes
* approximately 500ms on a 2017 device. Therefore, this method can be computationally
* expensive, and should not be called more than once an hour.
*
*
Data is only collected for UIDs passing the predicate supplied in {@link
* #setUidPredicate}.
*/
@Nullable
public ArrayList getProcessCpuUsage() {
if (DEBUG) {
Slog.d(TAG, "Reading CPU thread usages for processes owned by UIDs");
}
final ArrayList processCpuUsages = new ArrayList<>();
try (DirectoryStream processPaths =
Files.newDirectoryStream(mProcPath, PROCESS_DIRECTORY_FILTER)) {
for (Path processPath : processPaths) {
final int processId = getProcessId(processPath);
final int uid = mInjector.getUidForPid(processId);
if (uid == ID_ERROR || processId == ID_ERROR) {
continue;
}
if (!mUidPredicate.test(uid)) {
continue;
}
final ProcessCpuUsage processCpuUsage =
getProcessCpuUsage(processPath, processId, uid);
if (processCpuUsage != null) {
processCpuUsages.add(processCpuUsage);
}
}
} catch (IOException e) {
Slog.w(TAG, "Failed to iterate over process paths", e);
return null;
}
if (processCpuUsages.isEmpty()) {
Slog.w(TAG, "Didn't successfully get any process CPU information for UIDs specified");
return null;
}
if (DEBUG) {
Slog.d(TAG, "Read usage for " + processCpuUsages.size() + " processes");
}
return processCpuUsages;
}
/**
* Get the CPU frequencies that correspond to the times reported in {@link
* ThreadCpuUsage#usageTimesMillis}
*/
@Nullable
public int[] getCpuFrequenciesKhz() {
return mFrequenciesKhz;
}
/** Set the number of frequency buckets to use */
void setNumBuckets(int numBuckets) {
if (numBuckets < 1) {
Slog.w(TAG, "Number of buckets must be at least 1, but was " + numBuckets);
return;
}
// If `numBuckets` hasn't changed since the last set, do nothing
if (mFrequenciesKhz != null && mFrequenciesKhz.length == numBuckets) {
return;
}
mFrequencyBucketCreator =
new FrequencyBucketCreator(mProcTimeInStateReader.getFrequenciesKhz(), numBuckets);
mFrequenciesKhz =
mFrequencyBucketCreator.bucketFrequencies(
mProcTimeInStateReader.getFrequenciesKhz());
}
/** Set the UID predicate for {@link #getProcessCpuUsage} */
void setUidPredicate(Predicate uidPredicate) {
mUidPredicate = uidPredicate;
}
/**
* Read all of the CPU usage statistics for each child thread of a process
*
* @param processPath the {@code /proc} path of the thread
* @param processId the ID of the process
* @param uid the ID of the user who owns the process
* @return process CPU usage containing usage of all child threads. Null if the process exited
* and its {@code proc} directory was removed while collecting information
*/
@Nullable
private ProcessCpuUsage getProcessCpuUsage(Path processPath, int processId, int uid) {
if (DEBUG) {
Slog.d(
TAG,
"Reading CPU thread usages with directory "
+ processPath
+ " process ID "
+ processId
+ " and user ID "
+ uid);
}
final Path allThreadsPath = processPath.resolve("task");
final ArrayList threadCpuUsages = new ArrayList<>();
try (DirectoryStream threadPaths = Files.newDirectoryStream(allThreadsPath)) {
for (Path threadDirectory : threadPaths) {
ThreadCpuUsage threadCpuUsage = getThreadCpuUsage(threadDirectory);
if (threadCpuUsage == null) {
continue;
}
threadCpuUsages.add(threadCpuUsage);
}
} catch (IOException e) {
// Expected when a process finishes
return null;
}
// If we found no threads, then the process has exited while we were reading from it
if (threadCpuUsages.isEmpty()) {
return null;
}
if (DEBUG) {
Slog.d(TAG, "Read CPU usage of " + threadCpuUsages.size() + " threads");
}
return new ProcessCpuUsage(processId, getProcessName(processPath), uid, threadCpuUsages);
}
/**
* Get a thread's CPU usage
*
* @param threadDirectory the {@code /proc} directory of the thread
* @return thread CPU usage. Null if the thread exited and its {@code proc} directory was
* removed while collecting information
*/
@Nullable
private ThreadCpuUsage getThreadCpuUsage(Path threadDirectory) {
// Get the thread ID from the directory name
final int threadId;
try {
final String directoryName = threadDirectory.getFileName().toString();
threadId = Integer.parseInt(directoryName);
} catch (NumberFormatException e) {
Slog.w(TAG, "Failed to parse thread ID when iterating over /proc/*/task", e);
return null;
}
// Get the thread name from the thread directory
final String threadName = getThreadName(threadDirectory);
// Get the CPU statistics from the directory
final Path threadCpuStatPath = threadDirectory.resolve(CPU_STATISTICS_FILENAME);
final long[] cpuUsagesLong = mProcTimeInStateReader.getUsageTimesMillis(threadCpuStatPath);
if (cpuUsagesLong == null) {
return null;
}
int[] cpuUsages = mFrequencyBucketCreator.bucketValues(cpuUsagesLong);
return new ThreadCpuUsage(threadId, threadName, cpuUsages);
}
/** Get the command used to start a process */
private String getProcessName(Path processPath) {
final Path processNamePath = processPath.resolve(PROCESS_NAME_FILENAME);
final String processName = ProcStatsUtil.readSingleLineProcFile(processNamePath.toString());
if (processName != null) {
return processName;
}
return DEFAULT_PROCESS_NAME;
}
/** Get the name of a thread, given the {@code /proc} path of the thread */
private String getThreadName(Path threadPath) {
final Path threadNamePath = threadPath.resolve(THREAD_NAME_FILENAME);
final String threadName = ProcStatsUtil.readNullSeparatedFile(threadNamePath.toString());
if (threadName == null) {
return DEFAULT_THREAD_NAME;
}
return threadName;
}
/**
* Get the ID of a process from its path
*
* @param processPath {@code proc} path of the process
* @return the ID, {@link #ID_ERROR} if the path could not be parsed
*/
private int getProcessId(Path processPath) {
String fileName = processPath.getFileName().toString();
try {
return Integer.parseInt(fileName);
} catch (NumberFormatException e) {
Slog.w(TAG, "Failed to parse " + fileName + " as process ID", e);
return ID_ERROR;
}
}
/**
* Quantizes a list of N frequencies into a list of M frequencies (where M<=N)
*
* In order to reduce data sent from the device, we discard precise frequency information for
* an approximation. This is done by putting groups of adjacent frequencies into the same
* bucket, and then reporting that bucket under the minimum frequency in that bucket.
*
*
Many devices have multiple core clusters. We do not want to report frequencies from
* different clusters under the same bucket, so some complication arises.
*
*
Buckets are allocated evenly across all core clusters, i.e. they all have the same number
* of buckets regardless of how many frequencies they contain. This is done to reduce code
* complexity, and in practice the number of frequencies doesn't vary too much between core
* clusters.
*
*
If the number of buckets is not a factor of the number of frequencies, the remainder of
* the frequencies are placed into the last bucket.
*
*
It is possible to have less buckets than asked for, so any calling code can't assume that
* initializing with N buckets will use return N values. This happens in two scenarios:
*
*
* - There are less frequencies available than buckets asked for.
*
- There are less frequencies in a core cluster than buckets allocated to that core
* cluster.
*
*/
@VisibleForTesting
public static class FrequencyBucketCreator {
private final int mNumFrequencies;
private final int mNumBuckets;
private final int[] mBucketStartIndices;
@VisibleForTesting
public FrequencyBucketCreator(long[] frequencies, int targetNumBuckets) {
mNumFrequencies = frequencies.length;
int[] clusterStartIndices = getClusterStartIndices(frequencies);
mBucketStartIndices =
getBucketStartIndices(clusterStartIndices, targetNumBuckets, mNumFrequencies);
mNumBuckets = mBucketStartIndices.length;
}
/**
* Put an array of values into buckets. This takes a {@code long[]} and returns {@code
* int[]} as everywhere this method is used will have to do the conversion anyway, so we
* save time by doing it here instead
*
* @param values the values to bucket
* @return the bucketed usage times
*/
@VisibleForTesting
public int[] bucketValues(long[] values) {
Preconditions.checkArgument(values.length == mNumFrequencies);
int[] buckets = new int[mNumBuckets];
for (int bucketIdx = 0; bucketIdx < mNumBuckets; bucketIdx++) {
final int bucketStartIdx = getLowerBound(bucketIdx, mBucketStartIndices);
final int bucketEndIdx =
getUpperBound(bucketIdx, mBucketStartIndices, values.length);
for (int valuesIdx = bucketStartIdx; valuesIdx < bucketEndIdx; valuesIdx++) {
buckets[bucketIdx] += values[valuesIdx];
}
}
return buckets;
}
/** Get the minimum frequency in each bucket */
@VisibleForTesting
public int[] bucketFrequencies(long[] frequencies) {
Preconditions.checkArgument(frequencies.length == mNumFrequencies);
int[] buckets = new int[mNumBuckets];
for (int i = 0; i < buckets.length; i++) {
buckets[i] = (int) frequencies[mBucketStartIndices[i]];
}
return buckets;
}
/**
* Get the index in frequencies where each core cluster starts
*
* The frequencies for each cluster are given in ascending order, appended to each other.
* This means that every time there is a decrease in frequencies (instead of increase) a new
* cluster has started.
*/
private static int[] getClusterStartIndices(long[] frequencies) {
ArrayList indices = new ArrayList<>();
indices.add(0);
for (int i = 0; i < frequencies.length - 1; i++) {
if (frequencies[i] >= frequencies[i + 1]) {
indices.add(i + 1);
}
}
return ArrayUtils.convertToIntArray(indices);
}
/** Get the index in frequencies where each bucket starts */
private static int[] getBucketStartIndices(
int[] clusterStartIndices, int targetNumBuckets, int numFrequencies) {
int numClusters = clusterStartIndices.length;
// If we haven't got enough buckets for every cluster, we instead have one bucket per
// cluster, with the last bucket containing the remaining clusters
if (numClusters > targetNumBuckets) {
return Arrays.copyOfRange(clusterStartIndices, 0, targetNumBuckets);
}
ArrayList bucketStartIndices = new ArrayList<>();
for (int clusterIdx = 0; clusterIdx < numClusters; clusterIdx++) {
final int clusterStartIdx = getLowerBound(clusterIdx, clusterStartIndices);
final int clusterEndIdx =
getUpperBound(clusterIdx, clusterStartIndices, numFrequencies);
final int numBucketsInCluster;
if (clusterIdx != numClusters - 1) {
numBucketsInCluster = targetNumBuckets / numClusters;
} else {
// If we're in the last cluster, the bucket will contain the remainder of the
// frequencies
int previousBucketsInCluster = targetNumBuckets / numClusters;
numBucketsInCluster =
targetNumBuckets - (previousBucketsInCluster * (numClusters - 1));
}
final int numFrequenciesInCluster = clusterEndIdx - clusterStartIdx;
// If there are less frequencies than buckets in a cluster, we have one bucket per
// frequency, and do not use the remaining buckets
final int numFrequenciesInBucket =
Math.max(1, numFrequenciesInCluster / numBucketsInCluster);
for (int bucketIdx = 0; bucketIdx < numBucketsInCluster; bucketIdx++) {
int bucketStartIdx = clusterStartIdx + bucketIdx * numFrequenciesInBucket;
// If we've gone over the end index, ignore the rest of the buckets for this
// cluster
if (bucketStartIdx >= clusterEndIdx) {
break;
}
bucketStartIndices.add(bucketStartIdx);
}
}
return ArrayUtils.convertToIntArray(bucketStartIndices);
}
private static int getLowerBound(int index, int[] startIndices) {
return startIndices[index];
}
private static int getUpperBound(int index, int[] startIndices, int max) {
if (index != startIndices.length - 1) {
return startIndices[index + 1];
} else {
return max;
}
}
}
/** CPU usage of a process */
public static class ProcessCpuUsage {
public final int processId;
public final String processName;
public final int uid;
public ArrayList threadCpuUsages;
@VisibleForTesting
public ProcessCpuUsage(
int processId,
String processName,
int uid,
ArrayList threadCpuUsages) {
this.processId = processId;
this.processName = processName;
this.uid = uid;
this.threadCpuUsages = threadCpuUsages;
}
}
/** CPU usage of a thread */
public static class ThreadCpuUsage {
public final int threadId;
public final String threadName;
public int[] usageTimesMillis;
@VisibleForTesting
public ThreadCpuUsage(int threadId, String threadName, int[] usageTimesMillis) {
this.threadId = threadId;
this.threadName = threadName;
this.usageTimesMillis = usageTimesMillis;
}
}
/** Used to inject static methods from {@link Process} */
@VisibleForTesting
public static class Injector {
/** Get the UID for the process with ID {@code pid} */
public int getUidForPid(int pid) {
return Process.getUidForPid(pid);
}
}
}