Java GC日志行之间的区别是什么？ （“总时间......”与“[GC”）

Question

Java版本： 1.6.0_20

我在日志中看到以下内容，我正在尝试找出第一行和后续行之间的差异。据我所知，它们都是次要的GC相关，但是它们之间没有1对1，因为我读过的其他GC教程中通常都有。我知道如何解释第一行，第二行也很明显，但这两个事件有什么区别？

30171.470: [GC 30171.470: [ParNew: 32704K->64K(32704K), 0.0055740 secs] 1575471K->1545444K(3145664K), 0.0056610 secs] [Times: user=0.04 sys=0.00, real=0.01 secs]
Total time for which application threads were stopped: 0.0060020 seconds
Total time for which application threads were stopped: 0.0003300 seconds
Total time for which application threads were stopped: 0.0000740 seconds
Total time for which application threads were stopped: 0.0002630 seconds
Total time for which application threads were stopped: 0.0002640 seconds
Total time for which application threads were stopped: 0.0000760 seconds
... Snipped 35 similar lines ...
Total time for which application threads were stopped: 0.0006710 seconds
Total time for which application threads were stopped: 0.0000870 seconds
Total time for which application threads were stopped: 0.0002710 seconds
Total time for which application threads were stopped: 0.0000770 seconds
Total time for which application threads were stopped: 0.0002810 seconds
Total time for which application threads were stopped: 0.0002680 seconds
Total time for which application threads were stopped: 0.0000770 seconds
30289.137: [GC 30289.137: [ParNew: 32704K->63K(32704K), 0.0063990 secs] 1578084K->1548229K(3145664K), 0.0064890 secs] [Times: user=0.04 sys=0.00, real=0.01 secs]

感谢您的帮助！

Answer 1

“...应用程序线程..”消息由PrintGCApplicationStoppedTime控制。每当JVM到达safepoint操作结束时，它将检查是否应该打印应用程序在该操作期间停止的时间。

该标志的名称有些误导，因为它与GC没有特别的关系。例如，如果您还使用PrintSafepointStatistics标志运行，则可能会看到大多数VM操作都是RevokeBias。与GC相关的操作将命名为GenCollectForAllocation。