一次脚本测试的内存增长问题-编程知识

一次脚本测试的内存增长问题

问题背景

问题描述：进入应用的视频素材剪辑页面然后退出，脚本循环执行500次，内存增长156M

问题分析

分析增长曲线图

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曲线反映了从0到500次脚本执行过程中adb shell dumpsys meminfo抓取内存的增长情况，可以看出是Native内存一直增长未释放。

Profiler工具分析

将执行100的hprof和500次的hprof文件分别导入Android Studio的Profiler中。
100次
500次
可以看到“0 Leaks”，以及Native Size只增长了200k左右。至此，Profiler体现不出内存增长的原因。

MAT工具分析

hprof格式转换

利用sdk\platform-tools中的hprof-conv.exe将hprof转换为MAT可识别的文件

hprof对比

用MAT打开100次和500次的hprof文件，然后进行对比两份hprof
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可以看到WeakReference、ViewRootImpl.W、Cleaner和NativeAllocationRegistry.CleanerThunk的对象数量增长比较多。

分析ViewRootImpl.W

查看ViewRootImpl.W发现是一个和Window相关的Binder接口
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查看ViewRootImpl.W的引用关系，

发现是被Cleaner所持有，得出ViewRootImpl.W增长是因为Cleaner在增长。

分析Cleaner

查看源码

public class Cleaner extends PhantomReference<Object>
{// Dummy reference queue, needed because the PhantomReference constructor// insists that we pass a queue.  Nothing will ever be placed on this queue// since the reference handler invokes cleaners explicitly.//private static final ReferenceQueue<Object> dummyQueue = new ReferenceQueue<>();// Doubly-linked list of live cleaners, which prevents the cleaners// themselves from being GC'd before their referents//static private Cleaner first = null;private Cleanernext = null,prev = null;private static synchronized Cleaner add(Cleaner cl) {if (first != null) {cl.next = first;first.prev = cl;}first = cl;return cl;}private static synchronized boolean remove(Cleaner cl) {// If already removed, do nothingif (cl.next == cl)return false;// Update listif (first == cl) {if (cl.next != null)first = cl.next;elsefirst = cl.prev;}if (cl.next != null)cl.next.prev = cl.prev;if (cl.prev != null)cl.prev.next = cl.next;// Indicate removal by pointing the cleaner to itselfcl.next = cl;cl.prev = cl;return true;}private final Runnable thunk;private Cleaner(Object referent, Runnable thunk) {super(referent, dummyQueue);this.thunk = thunk;}/*** Creates a new cleaner.** @param  ob the referent object to be cleaned* @param  thunk*         The cleanup code to be run when the cleaner is invoked.  The*         cleanup code is run directly from the reference-handler thread,*         so it should be as simple and straightforward as possible.** @return  The new cleaner*/public static Cleaner create(Object ob, Runnable thunk) {if (thunk == null)return null;return add(new Cleaner(ob, thunk));}/*** Runs this cleaner, if it has not been run before.*/public void clean() {if (!remove(this))return;try {thunk.run();} catch (final Throwable x) {AccessController.doPrivileged(new PrivilegedAction<Void>() {public Void run() {if (System.err != null)new Error("Cleaner terminated abnormally", x).printStackTrace();System.exit(1);return null;}});}}}

查看引用关系
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可以看到Cleaner类是链表结构，不再好继续往下分析了。

分析WeakReference

从上面ViewRoomImpl.W源码可以看到有WeakReference类型的成员变量，推断WeakReference增长832次有400次是因为ViewRootImpl.W增长400次。用MAT合并虚引用、软引用和弱引用
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剩余没有被过滤的133个对象，查看存放的值有很多和音视频播放相关