垃圾优先垃圾收集器如何工作?
谁能解释一下 G1 垃圾收集器的工作原理?我还没有在任何地方找到任何全面、易于理解的描述.
Can someone explain how the G1 Garbage Collector works please? I haven't been able to find any comprehensive, easy-to-understand descriptions anywhere yet.
谢谢
推荐答案
收集器将堆分成固定大小的区域并跟踪这些区域中的实时数据.它保留了一组指针——记忆集"——进出该区域.当认为有必要进行 GC 时，它首先收集实时数据较少的区域(因此，垃圾优先").通常，这可能意味着一步收集整个区域:如果指向某个区域的指针数量为零，则不需要对该区域进行标记或扫描.
The collector splits the heap up into fixed-size regions and tracks the live data in those regions. It keeps a set of pointers — the "remembered set" — into and out of the region. When a GC is deemed necessary, it collects the regions with less live data first (hence, "garbage first"). Often, this can mean collecting an entire region in one step: if the number of pointers into a region is zero, then it doesn't need to do a mark or sweep of that region.
对于每个区域，它会跟踪描述收集它们需要多长时间的各种指标.您可以给它一个关于暂停时间的软实时约束，然后它会尝试在该受限时间内尽可能多地收集垃圾.
For each region, it tracks various metrics that describe how long it will take to collect them. You can give it a soft real-time constraint about pause times, and it then tries to collect as much garbage as it can in that constrained time.
有JavaOne谈G1，也有几篇关于这个话题的文章:
There is JavaOne talk about G1 and few articles on the topic:
- http://developers.sun.com/learning/javaoneonline/j1sessn.jsp
- http://www.fasterj.com/articles/G1.shtml
- http://www.drdobbs.com/java/219401061
- http://www.infoq.com/articles/G1-One-Garbage-Collector-To-Rule-Them-All
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