framework 级影响Android 各种性能响应时间相关

                                                                                           Android6.0系统 以上

1：影响APP启动， 发起启动APP进程到systemserver 解析得到resolve 包信息把启动命令写入到zygote 后，进入阻塞等待状态会等待 zygote 的返回值。目前这块原生代码没有超时处理。

[-> Process.java]

private static ProcessStartResult zygoteSendArgsAndGetResult(
        ZygoteState zygoteState, ArrayList args)
        throws ZygoteStartFailedEx {
    try {
        //其中zygoteState 【见小节3.1】
        final BufferedWriter writer = zygoteState.writer;
        final DataInputStream inputStream = zygoteState.inputStream;

        writer.write(Integer.toString(args.size()));
        writer.newLine();

        int sz = args.size();
        for (int i = 0; i < sz; i++) {
            String arg = args.get(i);
            if (arg.indexOf('\n') >= 0) {
                throw new ZygoteStartFailedEx(
                        "embedded newlines not allowed");
            }
            writer.write(arg);
            writer.newLine();
        }

        writer.flush();

        ProcessStartResult result = new ProcessStartResult();
        //等待socket服务端（即zygote）返回新创建的进程pid;
        //对于等待时长问题，Google正在考虑此处是否应该有一个timeout，但目前是没有的。
        result.pid = inputStream.readInt();
        if (result.pid < 0) {
            throw new ZygoteStartFailedEx("fork() failed");
        }
        result.usingWrapper = inputStream.readBoolean();
        return result;
    } catch (IOException ex) {
        zygoteState.close();
        throw new ZygoteStartFailedEx(ex);
    }
}

2：影响systemserver   被zygote fork 出来后会执行系统服务架包的ODEX优化，需要和install进程建立socket连接 会等待ping通为止。

[–>ZygoteInit.java]

private static void handleSystemServerProcess(
        ZygoteConnection.Arguments parsedArgs)
        throws ZygoteInit.MethodAndArgsCaller {

    closeServerSocket(); //关闭父进程zygote复制而来的Socket

    Os.umask(S_IRWXG | S_IRWXO);

    if (parsedArgs.niceName != null) {
        Process.setArgV0(parsedArgs.niceName); //设置当前进程名为"system_server"
    }

    final String systemServerClasspath = Os.getenv("SYSTEMSERVERCLASSPATH");
    if (systemServerClasspath != null) {
        //执行dex优化操作【见小节6】
        performSystemServerDexOpt(systemServerClasspath);
    }

    if (parsedArgs.invokeWith != null) {
        String[] args = parsedArgs.remainingArgs;

        if (systemServerClasspath != null) {
            String[] amendedArgs = new String[args.length + 2];
            amendedArgs[0] = "-cp";
            amendedArgs[1] = systemServerClasspath;
            System.arraycopy(parsedArgs.remainingArgs, 0, amendedArgs, 2, parsedArgs.remainingArgs.length);
        }
        //启动应用进程
        WrapperInit.execApplication(parsedArgs.invokeWith,
                parsedArgs.niceName, parsedArgs.targetSdkVersion,
                VMRuntime.getCurrentInstructionSet(), null, args);
    } else {
        ClassLoader cl = null;
        if (systemServerClasspath != null) {
            创建类加载器，并赋予当前线程
            cl = new PathClassLoader(systemServerClasspath, ClassLoader.getSystemClassLoader());
            Thread.currentThread().setContextClassLoader(cl);
        }

        //system_server故进入此分支【见小节7】
        RuntimeInit.zygoteInit(parsedArgs.targetSdkVersion, parsedArgs.remainingArgs, cl);
    }

    /* should never reach here */
}

此处systemServerClasspath环境变量主要有/system/framework/目录下的services.jar，ethernet-service.jar, wifi-service.jar这3个文件

[–>ZygoteInit.java]

private static void performSystemServerDexOpt(String classPath) {
    final String[] classPathElements = classPath.split(":");
    //创建一个与installd的建立socket连接
    final InstallerConnection installer = new InstallerConnection();
    //执行ping操作，直到与installd服务端连通为止
    installer.waitForConnection();
    final String instructionSet = VMRuntime.getRuntime().vmInstructionSet();

    try {
        for (String classPathElement : classPathElements) {
            final int dexoptNeeded = DexFile.getDexOptNeeded(
                    classPathElement, "*", instructionSet, false /* defer */);
            if (dexoptNeeded != DexFile.NO_DEXOPT_NEEDED) {
                //以system权限，执行dex文件优化
                installer.dexopt(classPathElement, Process.SYSTEM_UID, false,
                        instructionSet, dexoptNeeded);
            }
        }
    } catch (IOException ioe) {
        throw new RuntimeException("Error starting system_server", ioe);
    } finally {
        installer.disconnect(); //断开与installd的socket连接
    }
}

将classPath字符串中的架包，分别进行dex优化操作。真正执行优化工作通过socket通信将相应的命令参数，发送给installd来完成。

3：应用进程四大组件启动ANR。

• Service Timeout:比如前台服务在20s内未执行完成；
• BroadcastQueue Timeout：比如前台广播在10s内未执行完成
• ContentProvider Timeout：内容提供者,在publish过超时10s;
• InputDispatching Timeout: 输入事件分发超时5s，包括按键和触摸事件。

以service 为例子 Service Timeout是位于”ActivityManager”线程中的AMS.MainHandler收到 SERVICE_TIMEOUT_MSG 消息时触发。

对于Service有两类:

• 对于前台服务，则超时为SERVICE_TIMEOUT = 20s；
• 对于后台服务，则超时为SERVICE_BACKGROUND_TIMEOUT = 200s

由变量ProcessRecord.execServicesFg来决定是否前台启动

Service进程attach到system_server进程的过程中会调用realStartServiceLocked()方法来埋下炸弹.

[-> ActiveServices.java]

private final void realStartServiceLocked(ServiceRecord r,
        ProcessRecord app, boolean execInFg) throws RemoteException {
    ...
    //发送delay消息(SERVICE_TIMEOUT_MSG)，【见小节2.1.2】
    bumpServiceExecutingLocked(r, execInFg, "create");
    try {
        ...
        //最终执行服务的onCreate()方法
        app.thread.scheduleCreateService(r, r.serviceInfo,
                mAm.compatibilityInfoForPackageLocked(r.serviceInfo.applicationInfo),
                app.repProcState);
    } catch (DeadObjectException e) {
        mAm.appDiedLocked(app);
        throw e;
    } finally {
        ...
    }
}

private final void bumpServiceExecutingLocked(ServiceRecord r, boolean fg, String why) {
    ... 
    scheduleServiceTimeoutLocked(r.app);
}

void scheduleServiceTimeoutLocked(ProcessRecord proc) {
    if (proc.executingServices.size() == 0 || proc.thread == null) {
        return;
    }
    long now = SystemClock.uptimeMillis();
    Message msg = mAm.mHandler.obtainMessage(
            ActivityManagerService.SERVICE_TIMEOUT_MSG);
    msg.obj = proc;
    
    //当超时后仍没有remove该SERVICE_TIMEOUT_MSG消息，则执行service Timeout流程【见2.3.1】
    mAm.mHandler.sendMessageAtTime(msg,
        proc.execServicesFg ? (now+SERVICE_TIMEOUT) : (now+ SERVICE_BACKGROUND_TIMEOUT));
}

该方法的主要工作发送delay消息(SERVICE_TIMEOUT_MSG). 炸弹已埋下, 我们并不希望炸弹被引爆, 那么就需要在炸弹爆炸之前拆除炸弹.

在system_server进程AS.realStartServiceLocked()调用的过程会埋下一颗炸弹, 超时没有启动完成则会爆炸. 那么什么时候会拆除这颗炸弹的引线呢? 经过Binder等层层调用进入目标进程的主线程handleCreateService()的过程.

[-> ActivityThread.java]

    private void handleCreateService(CreateServiceData data) {
        ...
        java.lang.ClassLoader cl = packageInfo.getClassLoader();
        Service service = (Service) cl.loadClass(data.info.name).newInstance();
        ...

        try {
            //创建ContextImpl对象
            ContextImpl context = ContextImpl.createAppContext(this, packageInfo);
            context.setOuterContext(service);
            //创建Application对象
            Application app = packageInfo.makeApplication(false, mInstrumentation);
            service.attach(context, this, data.info.name, data.token, app,
                    ActivityManagerNative.getDefault());
            //调用服务onCreate()方法 
            service.onCreate();
            
            //拆除炸弹引线[见小节2.2.2]
            ActivityManagerNative.getDefault().serviceDoneExecuting(
                    data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);
        } catch (Exception e) {
            ...
        }
    }

在这个过程会创建目标服务对象,以及回调onCreate()方法, 紧接再次经过多次调用回到system_server来执行serviceDoneExecuting.

private void serviceDoneExecutingLocked(ServiceRecord r, boolean inDestroying,
            boolean finishing) {
    ...
    if (r.executeNesting <= 0) {
        if (r.app != null) {
            r.app.execServicesFg = false;
            r.app.executingServices.remove(r);
            if (r.app.executingServices.size() == 0) {
                //当前服务所在进程中没有正在执行的service
                mAm.mHandler.removeMessages(ActivityManagerService.SERVICE_TIMEOUT_MSG, r.app);
        ...
    }
    ...
}

该方法的主要工作是当service启动完成，则移除服务超时消息SERVICE_TIMEOUT_MSG。

前面介绍了埋炸弹和拆炸弹的过程, 如果在炸弹倒计时结束之前成功拆卸炸弹,那么就没有爆炸的机会, 但是世事难料. 总有些极端情况下无法即时拆除炸弹,导致炸弹爆炸, 其结果就是App发生ANR. 接下来,带大家来看看炸弹爆炸的现场:

在system_server进程中有一个Handler线程, 名叫”ActivityManager”.当倒计时结束便会向该Handler线程发送 一条信息SERVICE_TIMEOUT_MSG,

[-> ActivityManagerService.java ::MainHandler]

final class MainHandler extends Handler {
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case SERVICE_TIMEOUT_MSG: {
                ...
                //【见小节2.3.2】
                mServices.serviceTimeout((ProcessRecord)msg.obj);
            } break;
            ...
        }
        ...
    }
}

void serviceTimeout(ProcessRecord proc) {
    String anrMessage = null;

    synchronized(mAm) {
        if (proc.executingServices.size() == 0 || proc.thread == null) {
            return;
        }
        final long now = SystemClock.uptimeMillis();
        final long maxTime =  now -
                (proc.execServicesFg ? SERVICE_TIMEOUT : SERVICE_BACKGROUND_TIMEOUT);
        ServiceRecord timeout = null;
        long nextTime = 0;
        for (int i=proc.executingServices.size()-1; i>=0; i--) {
            ServiceRecord sr = proc.executingServices.valueAt(i);
            if (sr.executingStart < maxTime) {
                timeout = sr;
                break;
            }
            if (sr.executingStart > nextTime) {
                nextTime = sr.executingStart;
            }
        }
        if (timeout != null && mAm.mLruProcesses.contains(proc)) {
            Slog.w(TAG, "Timeout executing service: " + timeout);
            StringWriter sw = new StringWriter();
            PrintWriter pw = new FastPrintWriter(sw, false, 1024);
            pw.println(timeout);
            timeout.dump(pw, "    ");
            pw.close();
            mLastAnrDump = sw.toString();
            mAm.mHandler.removeCallbacks(mLastAnrDumpClearer);
            mAm.mHandler.postDelayed(mLastAnrDumpClearer, LAST_ANR_LIFETIME_DURATION_MSECS);
            anrMessage = "executing service " + timeout.shortName;
        }
    }

    if (anrMessage != null) {
        //当存在timeout的service，则执行appNotResponding
        mAm.appNotResponding(proc, null, null, false, anrMessage);
    }
}

其中anrMessage的内容为”executing service [发送超时serviceRecord信息]”;