java - Sun GC 最大保留阈值

Question

有一个关于 Sun GC 的问题。 Sun FAQ(1.4.2 的旧版)指出吞吐量收集器不使用 MaxTenuringThreshold (MTT) 参数。它仅用于 CMS。 http://java.sun.com/docs/hotspot/gc1.4.2/faq.html

(12) What should I do if my application has mid- or long-lived objects?

• Objects that survive a young generation collection have a copying cost (part of the algorithm for a young generation collection is to copy any objects that survive). Mid- or long-lived objects may be copied multiple times. Use the -XX option MaxTenuringThreshold to determine the copying costs. Use -XX:MaxTenuringThreshold=0 to move an object that survives a young generation collection immediately to the tenured generation. If that improves the performance of the application, the copying of long-lived objects is significant. Note that the throughput collector does not use the MaxTenuringThreshold parameter.

我不知道如何验证这一点，但如果这是真的，吞吐量收集器如何确定何时将年轻对象提升为终身代？是每次年轻代填满时就执行此操作吗(换句话说 MTT = 0 ？)。

Answer 1

如果您谈论的是现代 (1.6.0) Sun GC，您可以下载源代码并自己弄清楚到底发生了什么。但当然，行为可能会随着补丁级别的不同而改变。

以下是一些引用 -XXmaxTenuringThreshold 选项的最新文档:

• Java Tuning White Paper - 孙(2005)
• "The most complete list of -XX options for Java 6 JVM" - 尤金·库列绍夫 (2006)

Google 搜索中会显示各种提示。但我在网上找不到任何明确的文档或你的问题的明确答案。