java - Java G1 垃圾收集器是否尊重 MaxHeapFreeRatio 参数？

Question

Java G1 垃圾收集器(在 Open JDK 中实现)是否遵守 -XX:MaxHeapFreeRatio=n JVM 参数？

它在 Java 8 中是否尊重它？

我找到了 JEP 346: Promptly Return Unused Committed Memory from G1在 Java 12 中交付，但我不清楚它之前的状态。

Answer 1

我找到的一个非权威答案是基于https://bugs.openjdk.java.net/browse/JDK-8078039?focusedCommentId=13632717&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-13632717

Most notably, some GCs support it, some do not. This RFE doesn't say which GC is used, so I assume we are talking about the default GC which supports MaxHeapFreeRatio. G1 also supports this option.

To shrink the heap (and release memory) a full GC is required. It the application doesn't trigger a full GC manually, it may take a while before one is triggered by the JVM.

所以答案是(对于 Java 8):是的......但不是。

• 是的，它支持该选项
• 但只有当完全 GC 发生时，这可能永远不会发生

(我仍然很好奇在更现代的 JVM 中是否有更权威的来源以及当前状态)