所有代碼都是Android 11
ActivityManagerService 簡稱 AMS ,那么他在系統(tǒng)調(diào)用過程中是干什么的,他到底管理了什么,他在系統(tǒng)調(diào)度又充當了什么角色,我們接下來就開始具體分析一下,由于ActivityManagerService 是一個非常功能非常復(fù)雜且代碼特別龐大的一個類,想要了解ActivityManagerService 就需要將他里面非常多的功能拆分來講解一下,本篇博客我會先將 ActivityManagerService 的啟動流程說一下,了解一下 ActivityManagerService 在啟動過程中都持有了哪些比較重要的對象,后續(xù)在針對不同的對象做具體的分析
ActivityManagerService 簡稱 AMS
ActivityManagerService.Lifecycle.class 代理 AMS ,并創(chuàng)建ams
我的關(guān)于 FrameWork 的第一篇和第三篇都有介紹 SystemServer 通過 SystemServiceMananger 啟動各個服務(wù)的流程,同時我在前面的博客里面也多次提到,AMS的啟動流程與其他 SystemService 有些不同,那就不是他不會通過代理類將自身添加到ServiceManager , 那么他是如何被添加到ServiceManager 當中的呢,
mActivityManagerService = ActivityManagerService.Lifecycle.startService(
mSystemServiceManager, atm); // 啟動AMS
通過 ActivityManagerService.Lifecycle 這個代理類解決java 單一繼承的問題,來啟動 AMS , 并且將 AcivityTaskManagerService 作為參數(shù)傳入,AcivityTaskManagerService 是在android 10 版本中引入的一個功能,至于為什么要引入他,可能google 覺得 AMS 功能太復(fù)雜了,需要將部分功能繼續(xù)封裝一下吧
public static final class Lifecycle extends SystemService {
private final ActivityManagerService mService;
private static ActivityTaskManagerService sAtm;
public Lifecycle(Context context) {
super(context);
mService = new ActivityManagerService(context, sAtm);
}
public static ActivityManagerService startService(
SystemServiceManager ssm, ActivityTaskManagerService atm) {
sAtm = atm;
return ssm.startService(ActivityManagerService.Lifecycle.class).getService();
}
@Override
public void onStart() {
mService.start();
}
@Override
public void onBootPhase(int phase) {
mService.mBootPhase = phase;
if (phase == PHASE_SYSTEM_SERVICES_READY) {
mService.mBatteryStatsService.systemServicesReady();
mService.mServices.systemServicesReady();
} else if (phase == PHASE_ACTIVITY_MANAGER_READY) {
mService.startBroadcastObservers();
} else if (phase == PHASE_THIRD_PARTY_APPS_CAN_START) {
mService.mPackageWatchdog.onPackagesReady();
}
}
@Override
public void onUserStopped(@NonNull TargetUser user) {
mService.mBatteryStatsService.onCleanupUser(user.getUserIdentifier());
}
public ActivityManagerService getService() {
return mService;
}
}
代理類創(chuàng)建 AMS ,并且將 ATMS 作為參數(shù)給到 AMS ,我在前面說過 ams 并不是通過代理類將自身添加到 ServiceManager 當中的,那么他是如何添加進去的,帶著這個疑問,接下來看一下他的構(gòu)造方法
AMS 初始化方法 及內(nèi)容分析
public ActivityManagerService(Context systemContext, ActivityTaskManagerService atm) {
LockGuard.installLock(this, LockGuard.INDEX_ACTIVITY);
看起來像網(wǎng)絡(luò)管理
mInjector = new Injector(systemContext);
系統(tǒng)上下文，是在SystemServer進程fork出來后通過createSystemContext()創(chuàng)建的，即與SystemServer進程是一樣的
mContext = systemContext;
mFactoryTest = FactoryTest.getMode();
mSystemThread -->系統(tǒng)進程的主線程 sCurrentActivityThread，這里是systemMain()中創(chuàng)建的ActivityThread對象。即也與SystemServer一樣的。
mSystemThread = ActivityThread.currentActivityThread();
MUiContext-->是通過SystemContext 創(chuàng)建的一個ContextImpl,并且是綁定過 Resource ,package 信息 以及其他信息
mUiContext = mSystemThread.getSystemUiContext();
Slog.i(TAG, "Memory class: " + ActivityManager.staticGetMemoryClass());
一個HandlerThread 具有l(wèi)ooper
mHandlerThread = new ServiceThread(TAG,THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
mHandlerThread.start();
處理AMS消息的handle ,looper 沒使用SystemServer 的,使用的是上面創(chuàng)建的那個looper
mHandler = new MainHandler(mHandlerThread.getLooper());
UiHandler對應(yīng)于Android中的Ui線程 , 使用的是SystemServer 中的主線程中的looper
mUiHandler = mInjector.getUiHandler(this);
又一個HandlerThread 具有l(wèi)ooper
mProcStartHandlerThread = new ServiceThread(TAG + ":procStart",THREAD_PRIORITY_FOREGROUND, false /* allowIo */);
mProcStartHandlerThread.start();
綁定了上面looper的Handler
mProcStartHandler = new Handler(mProcStartHandlerThread.getLooper());
廠商定制修改這里
mConstants = new ActivityManagerConstants(mContext, this, mHandler);
管理Uid 的
final ActiveUids activeUids = new ActiveUids(this, true /* postChangesToAtm */);
持有了 platformService
mPlatformCompat = (PlatformCompat) ServiceManager.getService(Context.PLATFORM_COMPAT_SERVICE);
字面意思就是獲取進程列表
mProcessList = mInjector.getProcessList(this);
mProcessList.init(this, activeUids, mPlatformCompat);
啟動一個線程 while(true) 查看內(nèi)存情況, 也存在一個wait 機制,方法是waitForPressure ,不知道這個機制是什么樣的,但是確保不回一直遍歷
mLowMemDetector = new LowMemDetector(this);
這里面又創(chuàng)建了一個handlerThread,用來處理消息,這個類是用來減少后臺內(nèi)存的
mOomAdjuster = new OomAdjuster(this, mProcessList, activeUids);
// Broadcast policy parameters
final BroadcastConstants foreConstants = new BroadcastConstants(
Settings.Global.BROADCAST_FG_CONSTANTS);
foreConstants.TIMEOUT = BROADCAST_FG_TIMEOUT;
final BroadcastConstants backConstants = new BroadcastConstants(
Settings.Global.BROADCAST_BG_CONSTANTS);
backConstants.TIMEOUT = BROADCAST_BG_TIMEOUT;
final BroadcastConstants offloadConstants = new BroadcastConstants(
Settings.Global.BROADCAST_OFFLOAD_CONSTANTS);
offloadConstants.TIMEOUT = BROADCAST_BG_TIMEOUT;
// by default, no "slow" policy in this queue
offloadConstants.SLOW_TIME = Integer.MAX_VALUE;
mEnableOffloadQueue = SystemProperties.getBoolean(
"persist.device_config.activity_manager_native_boot.offload_queue_enabled", false);
創(chuàng)建幾種廣播相關(guān)對象，前臺廣播、后臺廣播、offload廣播隊列。
mFgBroadcastQueue = new BroadcastQueue(this, mHandler,
"foreground", foreConstants, false);
mBgBroadcastQueue = new BroadcastQueue(this, mHandler,
"background", backConstants, true);
mOffloadBroadcastQueue = new BroadcastQueue(this, mHandler,
"offload", offloadConstants, true);
mBroadcastQueues[0] = mFgBroadcastQueue;
mBroadcastQueues[1] = mBgBroadcastQueue;
mBroadcastQueues[2] = mOffloadBroadcastQueue;
創(chuàng)建ActiveServices對象，管理 ServiceRecord
mServices = new ActiveServices(this);
創(chuàng)建ProviderMap對象，管理ContentProviderRecord
mProviderMap = new ProviderMap(this);
mPackageWatchdog = PackageWatchdog.getInstance(mUiContext);
mAppErrors = new AppErrors(mUiContext, this, mPackageWatchdog);
final File systemDir = SystemServiceManager.ensureSystemDir();
創(chuàng)建電池統(tǒng)計服務(wù)，并輸出到制定目錄
mBatteryStatsService = new BatteryStatsService(systemContext, systemDir,
BackgroundThread.get().getHandler());
mBatteryStatsService.getActiveStatistics().readLocked();
mBatteryStatsService.scheduleWriteToDisk();
mOnBattery = DEBUG_POWER ? true
: mBatteryStatsService.getActiveStatistics().getIsOnBattery();
mBatteryStatsService.getActiveStatistics().setCallback(this);
mOomAdjProfiler.batteryPowerChanged(mOnBattery);
adb shell dumpsys procstats 查看應(yīng)用進程信息
mProcessStats = new ProcessStatsService(this, new File(systemDir, "procstats"));
//appops是在現(xiàn)有權(quán)限機制上新增的一套權(quán)限管理機制，主要針對一些高危的非必須系統(tǒng)應(yīng)用的權(quán)限，比如在其他應(yīng)用上顯示懸浮窗。
mAppOpsService = mInjector.getAppOpsService(new File(systemDir, "appops.xml"), mHandler);
mUgmInternal = LocalServices.getService(UriGrantsManagerInternal.class);
mUserController = new UserController(this);
mPendingIntentController = new PendingIntentController(
mHandlerThread.getLooper(), mUserController, mConstants);
if (SystemProperties.getInt("sys.use_fifo_ui", 0) != 0) {
mUseFifoUiScheduling = true;
}
mTrackingAssociations = "1".equals(SystemProperties.get("debug.track-associations"));
//Intent防火墻，Google定義了一組規(guī)則，來過濾intent，如果觸發(fā)了，則intent會被系統(tǒng)丟棄，
//且不會告知發(fā)送者
mIntentFirewall = new IntentFirewall(new IntentFirewallInterface(), mHandler);
得到ActivityTaskManagerService的對象，調(diào)用ATM.initialize
mActivityTaskManager = atm;
mActivityTaskManager.initialize(mIntentFirewall, mPendingIntentController,
DisplayThread.get().getLooper());
mAtmInternal = LocalServices.getService(ActivityTaskManagerInternal.class);
啟動一個線程專門跟進cpu當前狀態(tài)信息，ams對當前cpu狀態(tài)了如指掌，可以更加高效的安排其他工作
mProcessCpuThread = new Thread("CpuTracker") {
@Override
public void run() {
synchronized (mProcessCpuTracker) {
mProcessCpuInitLatch.countDown();
mProcessCpuTracker.init();
}
while (true) {
try {
try {
synchronized(this) {
final long now = SystemClock.uptimeMillis();
long nextCpuDelay = (mLastCpuTime.get()+MONITOR_CPU_MAX_TIME)-now;
long nextWriteDelay = (mLastWriteTime+BATTERY_STATS_TIME)-now;
//Slog.i(TAG, "Cpu delay=" + nextCpuDelay
// + ", write delay=" + nextWriteDelay);
if (nextWriteDelay < nextCpuDelay) {
nextCpuDelay = nextWriteDelay;
}
if (nextCpuDelay > 0) {
mProcessCpuMutexFree.set(true);
this.wait(nextCpuDelay);
}
}
} catch (InterruptedException e) {
}
updateCpuStatsNow();
} catch (Exception e) {
Slog.e(TAG, "Unexpected exception collecting process stats", e);
}
}
}
};
mHiddenApiBlacklist = new HiddenApiSettings(mHandler, mContext);
// 加入Watchdog的監(jiān)控，監(jiān)聽進程，這個類每分鐘調(diào)用一次監(jiān)視器，如果進程沒有任何返回就殺掉
Watchdog.getInstance().addMonitor(this);
Watchdog.getInstance().addThread(mHandler);
// bind background threads to little cores
// this is expected to fail inside of framework tests because apps can't touch cpusets directly
// make sure we've already adjusted system_server's internal view of itself first
保活這塊相關(guān)代碼
updateOomAdjLocked(OomAdjuster.OOM_ADJ_REASON_NONE);
try {
Process.setThreadGroupAndCpuset(BackgroundThread.get().getThreadId(),
Process.THREAD_GROUP_SYSTEM);
Process.setThreadGroupAndCpuset(
mOomAdjuster.mCachedAppOptimizer.mCachedAppOptimizerThread.getThreadId(),
Process.THREAD_GROUP_SYSTEM);
} catch (Exception e) {
Slog.w(TAG, "Setting background thread cpuset failed");
}
// ActivityManagerInternal類的實現(xiàn)類
mInternal = new LocalService();
mPendingStartActivityUids = new PendingStartActivityUids(mContext);
}
翻閱了很多資料,將所有能注釋的地方我都注釋了一下,其中非常有研究價值的是 關(guān)于?；?->updateOomAdjLocked 減少后臺內(nèi)存消耗-->OomAdjuster 與電池服務(wù)
在代理類的創(chuàng)建過程中會執(zhí)行他的start 方法
private void start() {
removeAllProcessGroups();
開啟cpu監(jiān)控
mProcessCpuThread.start();
將電量服務(wù)添加到ServiceManager中
mBatteryStatsService.publish();
浮窗加強管理添加到ServiceManager中
mAppOpsService.publish();
Slog.d("AppOps", "AppOpsService published");
LocalServices.addService(ActivityManagerInternal.class, mInternal);
mActivityTaskManager.onActivityManagerInternalAdded();
mPendingIntentController.onActivityManagerInternalAdded();
// Wait for the synchronized block started in mProcessCpuThread,
// so that any other access to mProcessCpuTracker from main thread
// will be blocked during mProcessCpuTracker initialization.
try {
mProcessCpuInitLatch.await();
} catch (InterruptedException e) {
Slog.wtf(TAG, "Interrupted wait during start", e);
Thread.currentThread().interrupt();
throw new IllegalStateException("Interrupted wait during start");
}
}
他的初始化和start方法就看完了, 從上面來看, AMS 可以 查看內(nèi)存情況 耗電情況 cpu 情況 并且管理者四大組件 安全策略 網(wǎng)絡(luò) 等各個服務(wù)的情況,還是非常有必要好好看一下的,
在SystemServer 初始化AMS 后,后續(xù)還調(diào)用了
mActivityManagerService.initPowerManagement();
初始化了電量服務(wù) 之后又調(diào)用了
mActivityManagerService.setSystemProcess();
public void setSystemProcess() {
try {
ServiceManager.addService(Context.ACTIVITY_SERVICE, this, /* allowIsolated= */ true,
DUMP_FLAG_PRIORITY_CRITICAL | DUMP_FLAG_PRIORITY_NORMAL | DUMP_FLAG_PROTO);
ServiceManager.addService(ProcessStats.SERVICE_NAME, mProcessStats);
ServiceManager.addService("meminfo", new MemBinder(this), /* allowIsolated= */ false,
DUMP_FLAG_PRIORITY_HIGH);
ServiceManager.addService("gfxinfo", new GraphicsBinder(this));
ServiceManager.addService("dbinfo", new DbBinder(this));
if (MONITOR_CPU_USAGE) {
ServiceManager.addService("cpuinfo", new CpuBinder(this),
/* allowIsolated= */ false, DUMP_FLAG_PRIORITY_CRITICAL);
}
ServiceManager.addService("permission", new PermissionController(this));
ServiceManager.addService("processinfo", new ProcessInfoService(this));
ServiceManager.addService("cacheinfo", new CacheBinder(this));
ApplicationInfo info = mContext.getPackageManager().getApplicationInfo(
"android", STOCK_PM_FLAGS | MATCH_SYSTEM_ONLY);
mSystemThread.installSystemApplicationInfo(info, getClass().getClassLoader());
synchronized (this) {
ProcessRecord app = mProcessList.newProcessRecordLocked(info, info.processName,
false,
0,
new HostingRecord("system"));
app.setPersistent(true);
app.pid = MY_PID;
app.getWindowProcessController().setPid(MY_PID);
app.maxAdj = ProcessList.SYSTEM_ADJ;
app.makeActive(mSystemThread.getApplicationThread(), mProcessStats);
addPidLocked(app);
mProcessList.updateLruProcessLocked(app, false, null);
updateOomAdjLocked(OomAdjuster.OOM_ADJ_REASON_NONE);
}
} catch (PackageManager.NameNotFoundException e) {
throw new RuntimeException(
"Unable to find android system package", e);
}
// Start watching app ops after we and the package manager are up and running.
mAppOpsService.startWatchingMode(AppOpsManager.OP_RUN_IN_BACKGROUND, null,
new IAppOpsCallback.Stub() {
@Override public void opChanged(int op, int uid, String packageName) {
if (op == AppOpsManager.OP_RUN_IN_BACKGROUND && packageName != null) {
if (getAppOpsManager().checkOpNoThrow(op, uid, packageName)
!= AppOpsManager.MODE_ALLOWED) {
runInBackgroundDisabled(uid);
}
}
}
});
final int[] cameraOp = {AppOpsManager.OP_CAMERA};
mAppOpsService.startWatchingActive(cameraOp, new IAppOpsActiveCallback.Stub() {
@Override
public void opActiveChanged(int op, int uid, String packageName, boolean active) {
cameraActiveChanged(uid, active);
}
});
}
在這里將他所持有的服務(wù)添加到 ServiceManager當中,這也解決了我們在看代碼過程中沒有發(fā)現(xiàn) AMS 將自己添加到ServiceManager當中的這么一個疑問
