| /* |
| * Copyright (C) 2019 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.server.am; |
| |
| import com.android.internal.annotations.GuardedBy; |
| |
| /** |
| * Detects low memory using PSI. |
| * |
| * If the kernel doesn't support PSI, then this class is not available. |
| */ |
| public final class LowMemDetector { |
| private static final String TAG = "LowMemDetector"; |
| private final ActivityManagerService mAm; |
| private final LowMemThread mLowMemThread; |
| private boolean mAvailable; |
| |
| private final Object mPressureStateLock = new Object(); |
| |
| @GuardedBy("mPressureStateLock") |
| private int mPressureState = MEM_PRESSURE_NONE; |
| |
| /* getPressureState return values */ |
| public static final int MEM_PRESSURE_NONE = 0; |
| public static final int MEM_PRESSURE_LOW = 1; |
| public static final int MEM_PRESSURE_MEDIUM = 2; |
| public static final int MEM_PRESSURE_HIGH = 3; |
| |
| LowMemDetector(ActivityManagerService am) { |
| mAm = am; |
| mLowMemThread = new LowMemThread(); |
| if (init() != 0) { |
| mAvailable = false; |
| } else { |
| mAvailable = true; |
| mLowMemThread.start(); |
| } |
| } |
| |
| public boolean isAvailable() { |
| return mAvailable; |
| } |
| |
| /** |
| * Returns the current mem factor. |
| * Note that getMemFactor returns LowMemDetector.MEM_PRESSURE_XXX |
| * which match ProcessStats.ADJ_MEM_FACTOR_XXX values. If they deviate |
| * there should be conversion performed here to translate pressure state |
| * into memFactor. |
| */ |
| public int getMemFactor() { |
| synchronized (mPressureStateLock) { |
| return mPressureState; |
| } |
| } |
| |
| private native int init(); |
| private native int waitForPressure(); |
| |
| private final class LowMemThread extends Thread { |
| public void run() { |
| |
| while (true) { |
| // sleep waiting for a PSI event |
| int newPressureState = waitForPressure(); |
| if (newPressureState == -1) { |
| // epoll broke, tear this down |
| mAvailable = false; |
| break; |
| } |
| // got a PSI event? let's update lowmem info |
| synchronized (mPressureStateLock) { |
| mPressureState = newPressureState; |
| } |
| } |
| } |
| } |
| } |