和你一起一生学习，这里是程序员 Android

利用在高通平台中的Performance机制，能够进步性能，比方利用的启动速度，滑动流畅性等。接下来就看下高通给咱们提供的Performance机制
1.该机制的JNI层实现局部位于

./vendor/qcom/proprietary/android-perf/QPerformance/jni/com_qualcomm_qti_Performance.cpp

下层实现位于 
Java代码

./vendor/qcom/proprietary/android-perf/QPerformance/src/com/qualcomm/qti/Performance.java

2.framework层的应用须要通过反射机制调用com.qualcomm.qti.Performance
具体实现在：

./frameworks/base/core/java/android/util/BoostFramework.java

在BoostFramework的构造函数中通过反射调用Performance对象，而BoostFramework中的好多办法是被hide掉的，可能是为了平安思考吧，在应用层无奈应用，只能在零碎层应用。当初举一个例子当利用启动时创立过程的时候能够应用高通给咱们提供的Performance机制。
在ActivityManagerService中，结构中会判断是否启动该机制

mIsLaunchBoostv2_enabled = mContext.getResources().getBoolean(                     com.android.internal.R.bool.config_enableLaunchBoostv2);  if(mIsLaunchBoostv2_enabled) {             lBoost_v2_TimeOut = mContext.getResources().getInteger(                     com.android.internal.R.integer.lboostv2_timeout_param);             lBoost_v2_ParamVal = mContext.getResources().getIntArray(                     com.android.internal.R.array.lboostv2_param_value);          }

在startProcessLocked中进行判断：

// Start launch boost v2                 if (mIsLaunchBoostv2_enabled == true && sPerfBoost_v2 == null) {                     sPerfBoost_v2 = new BoostFramework();                 }                 if (sPerfBoost_v2 != null) {                    sPerfBoost_v2.perfLockAcquire(lBoost_v2_TimeOut, lBoost_v2_ParamVal);                    sIsLaunchBoostv2_set = true;                 }

接下来看一下外围局部BoostFramework的实现
构造函数中通过反射取得Performance对象

public BoostFramework() {        if (mIsLoaded == false) {          try {              Class perfClass;              PathClassLoader perfClassLoader;         perfClassLoader = new PathClassLoader(PERFORMANCE_JAR,                                ClassLoader.getSystemClassLoader());              perfClass = perfClassLoader.loadClass(PERFORMANCE_CLASS);              mConstructor = perfClass.getConstructor();                Class[] argClasses = new Class[] {int.class, int[].class};              mAcquireFunc =  perfClass.getDeclaredMethod("perfLockAcquire", argClasses);              Log.v(TAG,"mAcquireFunc method = " + mAcquireFunc);                argClasses = new Class[] {};              mReleaseFunc =  perfClass.getDeclaredMethod("perfLockRelease", argClasses);              Log.v(TAG,"mReleaseFunc method = " + mReleaseFunc);                argClasses = new Class[] {MotionEvent.class, DisplayMetrics.class, int.class, int[].class};

之前调用的办法perfLockAcquire的真是面目

/** @hide */      public int perfLockAcquire(int duration, int... list) {          int ret = -1;          try {              Object retVal = mAcquireFunc.invoke(mPerf, duration, list);              ret = (int)retVal;          } catch(Exception e) {              Log.e(TAG,"Exception " + e);          }          return ret;      }

通过结构中的mAcquireFunc = perfClass.getDeclaredMethod("perfLockAcquire", argClasses);看其调用的还是Performance中的perfLockAcquire办法。
在Performance.java中会深刻到JNI层：

static {          try {              System.loadLibrary("qti_performance");          } catch (UnsatisfiedLinkError e) {          }      }  
/** &hide */      public int perfLockAcquire(int duration, int... list) {          int rc = REQUEST_SUCCEEDED;          handle = native_perf_lock_acq(handle, duration, list);          if (handle == 0)              rc = REQUEST_FAILED;          return rc;      }
原文链接：https://www.iteye.com/blog/42...

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