95 lines
2.9 KiB
Java
95 lines
2.9 KiB
Java
/*
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* Copyright (C) 2021 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.internal.os;
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import android.annotation.Nullable;
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/**
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* CPU tracking using eBPF.
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*
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* The tracking state and data about available frequencies are cached to avoid JNI calls and
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* creating temporary arrays. The data is stored in a format that is convenient for metrics
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* computation.
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*
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* Synchronization is not needed because the underlying native library can be invoked concurrently
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* and getters are idempotent.
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*/
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public final class KernelCpuBpfTracking {
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private static boolean sTracking = false;
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/** Cached mapping from frequency index to frequency in kHz. */
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private static long[] sFreqs = null;
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/** Cached mapping from frequency index to CPU cluster / policy. */
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private static int[] sFreqsClusters = null;
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private KernelCpuBpfTracking() {
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}
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/** Returns whether CPU tracking using eBPF is supported. */
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public static native boolean isSupported();
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/** Starts CPU tracking using eBPF. */
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public static boolean startTracking() {
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if (!sTracking) {
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sTracking = startTrackingInternal();
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}
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return sTracking;
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}
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private static native boolean startTrackingInternal();
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/** Returns frequencies in kHz on which CPU is tracked. Empty if not supported. */
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public static long[] getFreqs() {
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if (sFreqs == null) {
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long[] freqs = getFreqsInternal();
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if (freqs == null) {
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return new long[0];
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}
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sFreqs = freqs;
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}
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return sFreqs;
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}
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@Nullable
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static native long[] getFreqsInternal();
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/**
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* Returns the cluster (policy) number for each frequency on which CPU is tracked. Empty if
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* not supported.
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*/
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public static int[] getFreqsClusters() {
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if (sFreqsClusters == null) {
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int[] freqsClusters = getFreqsClustersInternal();
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if (freqsClusters == null) {
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return new int[0];
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}
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sFreqsClusters = freqsClusters;
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}
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return sFreqsClusters;
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}
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@Nullable
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private static native int[] getFreqsClustersInternal();
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/** Returns the number of clusters (policies). */
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public static int getClusters() {
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int[] freqClusters = getFreqsClusters();
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return freqClusters.length > 0 ? freqClusters[freqClusters.length - 1] + 1 : 0;
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}
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}
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