缓存与垃圾收集 GC and Cache

最新推荐文章于 2025-12-28 16:49:38 发布

原创最新推荐文章于 2025-12-28 16:49:38 发布 · 609 阅读

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文章标签：

#cache #dictionary #reference #performance #application #java

本文通过实验对比了在ActionScript中使用强引用与弱引用Dictionary对内存的影响。结果显示，使用弱引用能显著减少内存占用，并有助于垃圾回收。建议在实现缓存时采用弱引用以优化应用性能。

One of the performance tips is recycling whatever you created as long as the memory allows. In Java, it's pretty easy to implement a cache using weak references. In AS, it's easy too. You just use Dictionary.

Below code demonstrates the memory usage by the Dictionary when using strong reference v.s. weak references :

var dict:Dictionary = new Dictionary(true/false);

for(var i:int = 0; i < 999999999; i++) {
   dict[new Application()] = 1;
   if(i % 1000 == 0) {
      trace(i + " - memory: " + System.totalMemory);
   }
}

and the result:

No. of cycles	Memory usage in Mega bytes Dictionary - strong reference	Memory usage in Mega bytes Dictionary - weak reference
4000	24.2	12.3
8000	38.3	11.7
12000	51.8	11.3
16000	66.2	14.0
20000	79.5	13.6

Clearly, when you use weak reference with Dictionary, it dances perfectly with the garbage collector. You can use Dictionary to implement your own weak referenced cache. Beware though, Dictionary can only be configured with keys weak referenced, which may look awkward when you use it this way. My suggestion is that you wrap the functions in a class.