在Java中调用System.gc()会建议使用权的一代以及年轻一代的垃圾回收吗?

问题描述

在Java中(通过JMX)调用System.gc()时，它将尽职地(试图)清理年轻一代.这通常效果很好.不过，我从未见过它试图清理终身制.这使我想到两个问题:

1. 可以收集使用权的世代(即，这一代中是否确实存在垃圾，或者使用权的世代中的所有对象实际上仍具有对它们的实时引用)?
2. 如果，可以收集终身代，可以通过System.gc()完成，还是有另一种方式(不太可能)，或者我只需要等到我终身代人的空间用完了吗?

解决方案

http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html#other_considerations 指出，System.gc()触发了major集合，即包括使用权. >

您是否发现GC日志中不是这种情况?

When invoking System.gc() in java (via JMX), it will dutifully (attempt to) clean the young generation. This generally works very well. I have never seen it attempt to clean the tenured generation, though. This leads me to two questions:

1. Can the tenured generation even be collected (i.e. is there actually garbage in this generation, or do all objects in the tenured generation actually still have live references to them)?
2. If the tenured generation can be collected, can this be done via System.gc(), or is there another way to do it (unlikely), or will I simply have to wait until I run out of space in the tenured generation?

解决方案

http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html#other_considerations states that System.gc() triggers a major collection, i.e. including tenured.

Have you seen this not to be the case in the GC logs?

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