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/*
* Copyright (C) 2021 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;
/**
* CPU tracking using eBPF.
*
* The tracking state and data about available frequencies are cached to avoid JNI calls and
* creating temporary arrays. The data is stored in a format that is convenient for metrics
* computation.
*
* Synchronization is not needed because the underlying native library can be invoked concurrently
* and getters are idempotent.
*/
public final class KernelCpuBpfTracking {
private static boolean sTracking = false;
/** Cached mapping from frequency index to frequency in kHz. */
private static long[] sFreqs = null;
/** Cached mapping from frequency index to CPU cluster / policy. */
private static int[] sFreqsClusters = null;
private KernelCpuBpfTracking() {
}
/** Returns whether CPU tracking using eBPF is supported. */
public static native boolean isSupported();
/** Starts CPU tracking using eBPF. */
public static boolean startTracking() {
if (!sTracking) {
sTracking = startTrackingInternal();
}
return sTracking;
}
private static native boolean startTrackingInternal();
/** Returns frequencies in kHz on which CPU is tracked. Empty if not supported. */
public static long[] getFreqs() {
if (sFreqs == null) {
long[] freqs = getFreqsInternal();
if (freqs == null) {
return new long[0];
}
sFreqs = freqs;
}
return sFreqs;
}
@Nullable
static native long[] getFreqsInternal();
/**
* Returns the cluster (policy) number for each frequency on which CPU is tracked. Empty if
* not supported.
*/
public static int[] getFreqsClusters() {
if (sFreqsClusters == null) {
int[] freqsClusters = getFreqsClustersInternal();
if (freqsClusters == null) {
return new int[0];
}
sFreqsClusters = freqsClusters;
}
return sFreqsClusters;
}
@Nullable
private static native int[] getFreqsClustersInternal();
/** Returns the number of clusters (policies). */
public static int getClusters() {
int[] freqClusters = getFreqsClusters();
return freqClusters.length > 0 ? freqClusters[freqClusters.length - 1] + 1 : 0;
}
}
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