Android Q AppCompactor and LowMemDetector

1、在ActivityManagerService.java 中

OomAdjuster mOomAdjuster;final LowMemDetector mLowMemDetector;

mProcessList.init(this, activeUids);mLowMemDetector = null;mOomAdjuster = new OomAdjuster(this, mProcessList, activeUids);

2、在OomAdjuster.java 中

OomAdjuster(ActivityManagerService service, ProcessList processList, ActiveUids activeUids) {    mService = service;    mProcessList = processList;    mActiveUids = activeUids;    mLocalPowerManager = LocalServices.getService(PowerManagerInternal.class);    mConstants = mService.mConstants;    mAppCompact = new AppCompactor(mService);    // The process group is usually critical to the response time of foreground app, so the    // setter should apply it as soon as possible.    final ServiceThread adjusterThread = new ServiceThread(TAG, TOP_APP_PRIORITY_BOOST,            false /* allowIo */);    adjusterThread.start();    Process.setThreadGroupAndCpuset(adjusterThread.getThreadId(), THREAD_GROUP_TOP_APP);    mProcessGroupHandler = new Handler(adjusterThread.getLooper(), msg -> {        Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "setProcessGroup");        final int pid = msg.arg1;        final int group = msg.arg2;        try {            setProcessGroup(pid, group);        } catch (Exception e) {            if (DEBUG_ALL) {                Slog.w(TAG, "Failed setting process group of " + pid + " to " + group, e);            }        } finally {            Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);        }        return true;    });}

这里创建了mAppCompact 对象，及创建了一个服务进程用于oom 调节时设置进程cpu group 组

3、AppCompactor.java

public AppCompactor(ActivityManagerService am) {    mAm = am;    mCompactionThread = new ServiceThread("CompactionThread",            THREAD_PRIORITY_FOREGROUND, true);    mProcStateThrottle = new HashSet<>();}

4、初始化

mOomAdjuster.initSettings();

void initSettings() {    mAppCompact.init();}

/** * Reads phenotype config to determine whether app compaction is enabled or not and * starts the background thread if necessary. */public void init() {    DeviceConfig.addOnPropertiesChangedListener(DeviceConfig.NAMESPACE_ACTIVITY_MANAGER,            ActivityThread.currentApplication().getMainExecutor(), mOnFlagsChangedListener);    synchronized (mPhenotypeFlagLock) {        updateUseCompaction();//参加handle         updateCompactionActions();        updateCompactionThrottles();        updateStatsdSampleRate();        updateFullRssThrottle();        updateFullDeltaRssThrottle();        updateProcStateThrottle();    }    Process.setThreadGroupAndCpuset(mCompactionThread.getThreadId(),            Process.THREAD_GROUP_SYSTEM);}

/** * Reads the flag value from DeviceConfig to determine whether app compaction * should be enabled, and starts the compaction thread if needed. */@GuardedBy("mPhenotypeFlagLock")private void updateUseCompaction() {    mUseCompaction = DeviceConfig.getBoolean(DeviceConfig.NAMESPACE_ACTIVITY_MANAGER,                KEY_USE_COMPACTION, DEFAULT_USE_COMPACTION);    if (mUseCompaction && !mCompactionThread.isAlive()) {        mCompactionThread.start();        mCompactionHandler = new MemCompactionHandler(); //handle     }}

创建handle，设置参数，监听数据库字段参数，这些参数用户压缩时使用

https://www.jianshu.com/p/ae4ca096201a

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