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CPU优化及常用工具

原理与文章参考

• 编舞者、looper、JankStats方法

常用ADB

含义	命令	备注
查看CPU状态	adb shell top -H -d 1 -p pid -O cpu	-O cpu 查看对应在那个核心 ；修改采样间隔为1s
导出当前进程所有线程状态到tombstoned	adb shell run-as kill -3	实际上是以一个异常状态导出了，利用了墓碑机制
查看进程的所有线程	adb shell "ps -T	grep pid"
查看进程占用cpu情况	adb shell dumpsys cpuinfo	grep [进程名]
查看进程内线程占用cpu的情况	adb shell top -n 1 -d 0.5	grep proc_ id
获取设备cpu信息	adb shell cat /proc/cpuinfo	或者查看 /sys/devices/system/cpu 目录下的文件夹

常用原理、监控手段

原理

1. 普通手机默认60帧刷新率，相当于每帧16.6ms
2. 利用系统预留接口 对每个帧率/handler消息等 进行统计

监控手段

1. 设置looperPrinter
2. 字节码插桩检测慢函数（martix dokit）
3. 编舞者获取frame帧率
4. jetpack JankStats，获取丢帧信息

多线程并发解决耗时

线程池/数量参考

1. CPU密集：线程数设置为CPU核心数 + 1
2. IO密集：线程数设置为CPU核心数 * 2

UI相关

• 利用<font style="color:rgb(77, 77, 77);">IdelHandler</font>对一些常用view进行预绘制
• 通过排查布局，减少过度绘制

常见场景

• 过度绘制
• 频繁IO
• 主线程耗时任务

排查CPU占用过高

• 规范线程命名，定位线程
• 抓取top数据，查看具体哪个线程占用高
• cpu指标含义解释
• 线程各参数详解

常用系统/开源分析工具

AndroidStudio Profiler

• 抓取CPU火焰图，卡顿/ANR 主要监测主线程，是否会出现耗时操作

Systrace

• 官方指令参考
• 官方推荐指令 $ python systrace.py -o mynewtrace.html sched freq idle am wm gfx view binder_driver hal dalvik camera input res
• 要求环境

python2.7 安装
python six 模块，命令 : pip install six
“No module named win32con” 问题，安装相关： pip install pypiwin32

• 拉取到信息后用perfetto 打开即可 但是这个主要是针对系统的 对应用开发帮助不大，分析自己应用可以用btrace

Btrace

• 官方链接

Perfetto

• 官方-快速开始
• 工具界面
• 入门使用
• 线程状态

TraceView和 Profile

• traceview官方参考
• traceview使用
• 导出的日志分析
• 使用DDMS查看

新版路径：Sdk\tools\monitor.bat

• Incl Cpu Time：方法在CPU中执行所有时间（包含其调用的方法所消耗的时间）
• Excl Cpu Time: 方法在CPU中执行的时间（不包含其调用的方法所消耗的时间）
• Incl Real Time：方法运行消耗的所有时间（包含子方法）
• Excl Real Time：方法运行消耗的时间（不包含子方法）
• Calls + Recur Calls/Total ：方法调用、递归次数（重要指标，防止死循环）
• Cpu Time/Call ：该方法平均占用 CPU 的时间（重要指标，可以看出单个方法占用CPU的平均时间，但是要防止在个别调用处出现长时间占用，然后被平均了）
• Real Time/Call ：平均执行时间，包括切换、阻塞的时间（重要指标，可以看出单个方法执行的平均时间值，但是要防止在个别调用处出现长时间调用，然后被平均了）

• TraceView优势

可以精确埋点

Debug.startMethodTracing("sample");...
Debug.stopMethodTracing();

ANR相关

ANR原理及常见场景

• 原理

ANR（Application Not Responding）的监测原理本质上是消息机制，设定一个delay消息，超时未被移除则触发ANR。具体逻辑处理都在system server端，包括发送超时消息，移除超时消息，处理超时消息以及ANR弹框展示等；对于app而言，触发ANR的条件是主线程阻塞。

• 常见场景

1. Service ANR：前台20s，后台200s；startForeground超时10s
2. Broadcast ANR：前台10s，后台60s
3. Input ANR：按键或触摸事件在5s内无响应
4. ContentProvider ANR：10s，少见

ANR/卡顿检测

• 通过设置Looper的printer可以检测耗时
• WatchDog机制，子线程发送消息自增，休眠后检查
• 参考
• ANR日志导出

// 安卓21以下有权限可以获取到 anr 日志
private FileObserver fileObserver = null;
void initialize(....){// 实例化FileObserver ,监控路径"/data/anr/"，监听文件被写入fileObserver = new FileObserver("/data/anr/", CLOSE_WRITE) {public void onEvent(int event, String path) {try {if (path != null) {String filepath = "/data/anr/" + path;// 写入的文件是否有关键字 “trace”if (filepath.contains("trace")) {// 处理anr异常handleAnr(filepath);}}} catch (Exception e) {XCrash.getLogger().e(Util.TAG, "AnrHandler fileObserver onEvent failed", e);}}};try {// 启动FileObserver 监控fileObserver.startWatching();} catch (Exception e) {fileObserver = null;XCrash.getLogger().e(Util.TAG, "AnrHandler fileObserver startWatching failed", e);}
}private void handleAnr(String filepath) {...// 读取anr文件 /data/anr/trace*.txt。返回文件内容String trace = getTrace(filepath, anrTime.getTime());//删除其他的anr异常日志文件if (!FileManager.getInstance().maintainAnr()) {return;}//获取  tombstone 的文件头String emergency = null;try {emergency = getEmergency(anrTime, trace);} catch (Exception e) {XCrash.getLogger().e(Util.TAG, "AnrHandler getEmergency failed", e);}// 创建anr异常日志保存文件File logFile = null;try {String logPath = String.format(Locale.US, "%s/%s_%020d_%s__%s%s", logDir, Util.logPrefix, anrTime.getTime() * 1000, appVersion, processName, Util.anrLogSuffix);logFile = FileManager.getInstance().createLogFile(logPath);} catch (Exception e) {XCrash.getLogger().e(Util.TAG, "AnrHandler createLogFile failed", e);}if (logFile != null){// 根据配置将日志文件头，traces，logcat日志保存在文件中。}
}// 高版本通过AMS获取日志
public class ANRMoniter implements Runnable {private final String TAG = "ANRMoniter";private HandlerThread handlerThread = new HandlerThread("WatchMainHandler");private ILog logImpl;private Application app;private Handler watchHandler;private Handler mainHandler;private ScheduleCheckTask scheduleCheckTask;private int CHECK_INTERVAL = 5_000;public ANRMoniter(Application app, ILog logImpl) {this.app = app;this.logImpl = logImpl;init();}private void init() {handlerThread.start();Looper looper = handlerThread.getLooper();watchHandler = new Handler(looper);mainHandler = new Handler(Looper.getMainLooper());scheduleCheckTask = new ScheduleCheckTask();}public void start() {watchHandler.post(this);}@Overridepublic void run() {mainHandler.post(scheduleCheckTask);long endTime = System.currentTimeMillis() + CHECK_INTERVAL;long sleepTime = endTime - System.currentTimeMillis();while (sleepTime > 0) {try {Thread.sleep(sleepTime);} catch (InterruptedException e) {e.printStackTrace();}sleepTime = endTime - System.currentTimeMillis();}if (scheduleCheckTask.isBlocking()) {logImpl.Loge(TAG,"main handler blocking");checkRealANR(mainHandler.getLooper().getThread().getStackTrace());}scheduleCheckTask.reset();watchHandler.post(this);}private void checkRealANR(StackTraceElement[] stack) {ThreadPool.getInstance().execute(new Runnable() {@Overridepublic void run() {ActivityManager.ProcessErrorStateInfo processErrorStateInfo = getANRInfo(app);if (processErrorStateInfo != null) {logImpl.Loge(TAG,"ANR action");//real ANRRuntimeException e = new RuntimeException(processErrorStateInfo.shortMsg);e.setStackTrace(stack);e.printStackTrace();logImpl.Loge(TAG,e.getMessage());}}});}private ActivityManager.ProcessErrorStateInfo getANRInfo(Application app) {try {final long sleepTime = 500L;final long loop = 20;long times = 0;do {ActivityManager activityManager = (ActivityManager) app.getSystemService(Context.ACTIVITY_SERVICE);List<ActivityManager.ProcessErrorStateInfo> processesInErrorState = activityManager.getProcessesInErrorState();if (processesInErrorState != null) {for (ActivityManager.ProcessErrorStateInfo proc : processesInErrorState) {if (proc.condition == ActivityManager.ProcessErrorStateInfo.NOT_RESPONDING) {return proc;}}}Thread.sleep(sleepTime);} while (times++ < loop);} catch (Exception e) {e.printStackTrace();}return null;}private class ScheduleCheckTask implements Runnable {private boolean isBlocking;ScheduleCheckTask() {isBlocking = true;}@Overridepublic void run() {isBlocking = false;}public boolean isBlocking() {return isBlocking;}public void reset() {isBlocking = true;}}
}

• 自定义线程WatchDog参考

package com.aispeech.util;import android.os.Handler;
import android.os.HandlerThread;
import android.os.Looper;
import android.os.Message;
import android.util.Log;import com.aispeech.common.ThreadNameUtil;
import com.aispeech.lite.BaseKernel;import java.util.Vector;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;/**
* Description: 检测Kernel层 是否阻塞的工具类
* Author: junlong.huang
* CreateTime: 2023/8/21
*/
public class KernelWatchDog {private static final String TAG = "KernelWatchDog";HandlerThread innerThread;Handler innerHandler;long timeoutMillis = 2000;static final int MSG_INCREMENT = 0x01;private static volatile KernelWatchDog mInstance;private ConcurrentHashMap<BaseKernel, AtomicInteger> monitorMap;private Vector<BaseKernel> removeList;public static KernelWatchDog getInstance() {if (mInstance == null) {synchronized (KernelWatchDog.class) {if (mInstance == null) {mInstance = new KernelWatchDog();}}}return mInstance;}private KernelWatchDog() {init();}private void init() {monitorMap = new ConcurrentHashMap<>();removeList = new Vector<>();innerThread = new HandlerThread(ThreadNameUtil.getSimpleThreadName("watchdog-k"));innerThread.start();innerHandler = new InnerHandler(innerThread.getLooper());innerHandler.sendMessage(innerHandler.obtainMessage(MSG_INCREMENT));}public void addChecker(BaseKernel baseKernel) {Log.i(TAG, "addChecker:" + baseKernel.getInnerThreadName());monitorMap.put(baseKernel, new AtomicInteger(baseKernel.getTick()));}public void removeChecker(BaseKernel baseKernel) {if (monitorMap.containsKey(baseKernel)) {Log.i(TAG, "removeChecker: " + baseKernel.getInnerThreadName());monitorMap.remove(baseKernel);}}class InnerHandler extends Handler {public InnerHandler(Looper looper) {super(looper);}@Overridepublic void handleMessage(Message msg) {super.handleMessage(msg);if (innerHandler == null) return;switch (msg.what) {case MSG_INCREMENT:if (monitorMap == null || monitorMap.size() == 0) {innerHandler.sendMessageDelayed(innerHandler.obtainMessage(MSG_INCREMENT), timeoutMillis);break;}for (BaseKernel baseKernel : monitorMap.keySet()) {if (baseKernel.getInnerThread() != null &&!baseKernel.getInnerThread().isAlive()) {Log.i(TAG, "Detected thread quit,Add to list to be removed");removeList.add(baseKernel);continue;}AtomicInteger lastTick = monitorMap.get(baseKernel);if (lastTick == null) lastTick = new AtomicInteger(baseKernel.getTick());if (lastTick.get() != baseKernel.getTick()) {Log.w(TAG, "Detected target thread may blocked,export thread stack");Thread innerThread = baseKernel.getInnerThread();if (innerThread != null) {Log.w(TAG, getThreadStack(innerThread.getStackTrace()));}}lastTick.incrementAndGet();baseKernel.tick();}for (BaseKernel baseKernel : removeList) {monitorMap.remove(baseKernel);}removeList.clear();innerHandler.sendMessageDelayed(innerHandler.obtainMessage(MSG_INCREMENT), timeoutMillis);break;}}}public void release() {innerHandler.removeMessages(MSG_INCREMENT);innerThread.quit();monitorMap.clear();removeList.clear();}private String getThreadStack(StackTraceElement[] elements) {StringBuilder stackTraceString = new StringBuilder();for (StackTraceElement element : elements) {stackTraceString.append(element.toString()).append("\n");}return stackTraceString.toString();}}

卡顿检测

• matrix 字节码插桩，慢函数检测
• 采样率法，通过一个外置的工作线程Handler，按一段时间采样，如果大部分都是某个方法，则这个方法可能存在风险点

/**
* 按照一定频率采样
* 目标是找到卡顿时刻前后的堆栈，做大致定位，无法做到精准定位
* 原则上采样越高，定位越精准
* 还有，目前只采样了java层的堆栈，c层的需要另外实现，这个后续补充
*/
public class CallstackSampler {private static final String TAG = "CallstackSampler";private final Thread thread;private final Handler mHandler;private final long sThreshold = 1000;private final Runnable mRunnable = new Runnable() {@Overridepublic void run() {doSample();mHandler.postDelayed(this, sThreshold);}};public CallstackSampler(Thread thread) {this.thread = thread;HandlerThread mWorkThread = new HandlerThread("StackSampler" + thread.getName());mWorkThread.start();mHandler = new Handler(mWorkThread.getLooper());}private void doSample() {// 采集指定线程当前堆栈信息StackTraceElement[] stackTrace = thread.getStackTrace();String stackTraceString = Arrays.toString(stackTrace);if (!stackTraceString.contains("nativePollOnce")) {Log.d(TAG, thread.getName() + " Callstack sample taken at time: " + System.currentTimeMillis() + " " + stackTraceString);}}public void startSampling() {mHandler.postDelayed(mRunnable, sThreshold);}public void stopSampling() {mHandler.removeCallbacks(mRunnable);}
}

• 主线程耗时检测：设置一个printer

CPU 优化案例

1. 线程池复用，减少CPU调度开销
2. 资源拷贝优化，减少读取IO时间
3. 线程命名，方便定位问题
4. 非必要内容，延迟初始化
5. 初始化任务优先级分配，削峰填谷