android 开机优化(类和资源预加载优化)
转自:https://blog.csdn.net/xxm282828/article/details/49095839
Android启动过程中针对类和资源部分预加载耗时比较久,这个部分需要优化,主要涉及的文件:
./base/core/java/com/android/internal/os/ZygoteInit.java
主要采取三个措施:
1. 修改ZygoteInit.java 中预加载资源函数preload() , preloadClasses(); 与 preloadResources(); 并行加载。2. 修改读取配置信息过程中GC频率。3. 提升进程优先级
1、资源和类并行加载:
static void preload() { // Thread preloadRsThread = new Thread(new Runnable(){ @Override public void run() { // TODO Auto-generated method stub //将该资源加载放在子线程中 。加载资源文件要比加载classes文件要快,因此这里不提升子线程优先级。 preloadResources(); } }) ; preloadRsThread.start() ; preloadClasses(); //wait preloadRes complete. try { preloadRsThread.join() ; } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } //暴露什么问题。 preloadOpenGL(); }
2、减少GC的频繁调度:
/** * Performs Zygote process initialization. Loads and initializes * commonly used classes. * * Most classes only cause a few hundred bytes to be allocated, but * a few will allocate a dozen Kbytes (in one case, 500+K). */ private static void preloadClasses() { final VMRuntime runtime = VMRuntime.getRuntime(); InputStream is = ClassLoader.getSystemClassLoader().getResourceAsStream( PRELOADED_CLASSES); if (is == null) { Log.e(TAG, "Couldn't find " + PRELOADED_CLASSES + "."); } else { Log.i(TAG, "Preloading classes..."); long startTime = SystemClock.uptimeMillis(); // Drop root perms while running static initializers. setEffectiveGroup(UNPRIVILEGED_GID); setEffectiveUser(UNPRIVILEGED_UID); // Alter the target heap utilization. With explicit GCs this // is not likely to have any effect. float defaultUtilization = runtime.getTargetHeapUtilization(); runtime.setTargetHeapUtilization(0.8f); // Start with a clean slate. System.gc(); runtime.runFinalizationSync(); Debug.startAllocCounting(); try { BufferedReader br = new BufferedReader(new InputStreamReader(is), 256); int count = 0; String line; while ((line = br.readLine()) != null) { // Skip comments and blank lines. line = line.trim(); if (line.startsWith("#") || line.equals("")) { continue; } try { if (false) { Log.v(TAG, "Preloading " + line + "..."); } Class.forName(line); //减少GC频率,modify begin if (count%128==0&&Debug.getGlobalAllocSize() > PRELOAD_GC_THRESHOLD) {//end if (false) { Log.v(TAG, " GC at " + Debug.getGlobalAllocSize()); } System.gc(); runtime.runFinalizationSync(); Debug.resetGlobalAllocSize(); } count++; } catch (ClassNotFoundException e) { Log.w(TAG, "Class not found for preloading: " + line); } catch (UnsatisfiedLinkError e) { Log.w(TAG, "Problem preloading " + line + ": " + e); } catch (Throwable t) { Log.e(TAG, "Error preloading " + line + ".", t); if (t instanceof Error) { throw (Error) t; } if (t instanceof RuntimeException) { throw (RuntimeException) t; } throw new RuntimeException(t); } } Log.i(TAG, "...preloaded " + count + " classes in " + (SystemClock.uptimeMillis()-startTime) + "ms."); } catch (IOException e) { Log.e(TAG, "Error reading " + PRELOADED_CLASSES + ".", e); } finally { IoUtils.closeQuietly(is); // Restore default. runtime.setTargetHeapUtilization(defaultUtilization); // Fill in dex caches with classes, fields, and methods brought in by preloading. runtime.preloadDexCaches(); Debug.stopAllocCounting(); // Bring back root. We'll need it later. setEffectiveUser(ROOT_UID); setEffectiveGroup(ROOT_GID); } } }
3、提升进程的优先级
// ZygoteInit.java入口 public static void main(String argv[]) { try { //优化开机速度 begin /* 20150127 begin */ //获取当前进程优先级 int currentPriority = Process.getThreadPriority(Process.myPid()) ; //提升当前进程优先级。 Process.setThreadPriority(Process.THREAD_PRIORITY_AUDIO) ; /* 20150127 end */ // Start profiling the zygote initialization. SamplingProfilerIntegration.start(); //1.注册socket服务端 registerZygoteSocket(); EventLog.writeEvent(LOG_BOOT_PROGRESS_PRELOAD_START, SystemClock.uptimeMillis()); //5.加载资源 preload(); EventLog.writeEvent(LOG_BOOT_PROGRESS_PRELOAD_END, SystemClock.uptimeMillis()); // Finish profiling the zygote initialization. SamplingProfilerIntegration.writeZygoteSnapshot(); // Do an initial gc to clean up after startup gc(); /* 20150127 begin */ Process.setThreadPriority(currentPriority) ; /* 20150127 end */ //优化开机速度 end // Disable tracing so that forked processes do not inherit stale tracing tags from // Zygote. Trace.setTracingEnabled(false); // If requested, start system server directly from Zygote if (argv.length != 2) { throw new RuntimeException(argv[0] + USAGE_STRING); } //2. 调用starySystemServer()方法 if (argv[1].equals("start-system-server")) { startSystemServer(); } else if (!argv[1].equals("")) { throw new RuntimeException(argv[0] + USAGE_STRING); } Log.i(TAG, "Accepting command socket connections"); //3.循环监听并接收客户端请求。 runSelectLoop(); //关闭socket closeServerSocket(); } catch (MethodAndArgsCaller caller) { //4 《深入理解Android卷1》作者说这里比较重要 caller.run(); } catch (RuntimeException ex) { Log.e(TAG, "Zygote died with exception", ex); closeServerSocket(); throw ex; } }
4、修改gc调用阀值
/** when preloading, GC after allocating this many bytes * * 20150127 优化开机速度 */ //- private static final int PRELOAD_GC_THRESHOLD = 50000; private static final int PRELOAD_GC_THRESHOLD = 64*1024*1024; /*20150127 优化开机速度 end*/
另外,Android系统启动过程中,会预先加载资源文件,这些文件中,包含了很多系统应用会频繁使用到的资源文件,比如图片资源等。因此,我们自己的新添加其他的部分资源也可以预先加载到内存,这样不仅提升响应速度,而且也可以加快应用的冷启动速度(不过对于系统启动速度比较敏感的设备,不建议这么使用)。
5、关于进程优先级
Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND); //设置线程优先级为后台,这样当多个线程并发后很多无关紧要的线程分配的CPU时间将会减少,有利于主线程的处理,有以下几种:
int THREAD_PRIORITY_AUDIO //标准音乐播放使用的线程优先级
int THREAD_PRIORITY_BACKGROUND //标准后台程序
int THREAD_PRIORITY_DEFAULT // 默认应用的优先级
int THREAD_PRIORITY_DISPLAY //标准显示系统优先级,主要是改善UI的刷新
int THREAD_PRIORITY_FOREGROUND //标准前台线程优先级
int THREAD_PRIORITY_LESS_FAVORABLE //低于favorable
int THREAD_PRIORITY_LOWEST //有效的线程最低的优先级
int THREAD_PRIORITY_MORE_FAVORABLE //高于favorable
int THREAD_PRIORITY_URGENT_AUDIO //标准较重要音频播放优先级
int THREAD_PRIORITY_URGENT_DISPLAY //标准较重要显示优先级,对于输入事件同样适用
Thread.setPriority:是JDK提供的设置线程优先级的方法.
android.os.Process.setThreadPriority: 是android.jar 专门针对dalvik来进行设置线程优先级的方法;此方法更适合Android上面设置优先级,它设置的优先级更直接的适应在dalvik(Linux) 上的进程的优先级
注意在使用进行优先级设置的时候,如果提升当前进行的优先级,如果主进程优先级比较低,那么在系统启动过程中当前进程共享 主进程的资源直接导致系统启动延迟。
参考:https://my.oschina.net/kingguary/blog/1573951
https://blog.csdn.net/xxm282828/article/details/49095839
更多相关文章
- android异步任务完成后再执行主线程任务
- android转屏,切换屏幕,横竖屏(onConfigurationChanged)会重新加载 On
- android底图局部加载移动
- Android 页面或文件或网络请求时的加载动画
- Android使用线程获取网络图片的方法
- android中使用多线程——HandlerThread举例
- android 多线程断点下载,listview 模式 开始 暂停等功能
- [置顶] android中OnScrollListener的详解(Listview分批加载用到)