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/*
* Copyright (C) 2015 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.text.TextUtils;
import android.system.OsConstants;
import android.util.Slog;
import libcore.io.Libcore;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.Arrays;
/**
* Reads CPU time of a specific core spent at various frequencies and provides a delta from the
* last call to {@link #readDelta}. Each line in the proc file has the format:
*
* freq time
*
* where time is measured in jiffies.
*/
public class KernelCpuSpeedReader {
private static final String TAG = "KernelCpuSpeedReader";
private final String mProcFile;
private final long[] mLastSpeedTimes;
private final long[] mDeltaSpeedTimes;
// How long a CPU jiffy is in milliseconds.
private final long mJiffyMillis;
/**
* @param cpuNumber The cpu (cpu0, cpu1, etc) whose state to read.
*/
public KernelCpuSpeedReader(int cpuNumber, int numSpeedSteps) {
mProcFile = String.format("/sys/devices/system/cpu/cpu%d/cpufreq/stats/time_in_state",
cpuNumber);
mLastSpeedTimes = new long[numSpeedSteps];
mDeltaSpeedTimes = new long[numSpeedSteps];
long jiffyHz = Libcore.os.sysconf(OsConstants._SC_CLK_TCK);
mJiffyMillis = 1000/jiffyHz;
}
/**
* The returned array is modified in subsequent calls to {@link #readDelta}.
* @return The time (in milliseconds) spent at different cpu speeds since the last call to
* {@link #readDelta}.
*/
public long[] readDelta() {
try (BufferedReader reader = new BufferedReader(new FileReader(mProcFile))) {
TextUtils.SimpleStringSplitter splitter = new TextUtils.SimpleStringSplitter(' ');
String line;
int speedIndex = 0;
while (speedIndex < mLastSpeedTimes.length && (line = reader.readLine()) != null) {
splitter.setString(line);
Long.parseLong(splitter.next());
long time = Long.parseLong(splitter.next()) * mJiffyMillis;
if (time < mLastSpeedTimes[speedIndex]) {
// The stats reset when the cpu hotplugged. That means that the time
// we read is offset from 0, so the time is the delta.
mDeltaSpeedTimes[speedIndex] = time;
} else {
mDeltaSpeedTimes[speedIndex] = time - mLastSpeedTimes[speedIndex];
}
mLastSpeedTimes[speedIndex] = time;
speedIndex++;
}
} catch (IOException e) {
Slog.e(TAG, "Failed to read cpu-freq: " + e.getMessage());
Arrays.fill(mDeltaSpeedTimes, 0);
}
return mDeltaSpeedTimes;
}
}
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