java - GC 日志 - VM 操作事件 - 如何跟踪它们

Question

我正在使用 GCViewer 检查一些 GC 日志。 (请检查下面的屏幕截图)

我收到很多暂停(红色矩形)，这似乎与“vm 操作事件(应用程序已停止...)”有关。这些似乎与常规和完整的 GC 停止不同。

• 我如何才能知道哪些操作触发了停止事件？ (是否有用于此的 JVM 标志？)

• 它们与垃圾回收有什么不同？就 GCViewer 而言，Full GC Pauses + GC Pauses != Total Pause

Answer 1

添加 -XX:+PrintSafepointStatistics –XX:PrintSafepointStatisticsCount=1 将提供有关触发停止事件的操作的信息。

发件人:this link

When safepoints are used?

Below are few reasons for HotSpot JVM to initiate a safepoint:

• Garbage collection pauses
• Code deoptimization
• Flushing code cache
• Class redefinition (e.g. hot swap or instrumentation)
• Biased lock revocation
• Various debug operation (e.g. deadlock check or stacktrace dump)

要将日志写入文件，这取决于您使用的 VM 版本。

对于所有 Java 版本: Java 8 Docs .

-Xloggc:filename

Sets the file to which verbose GC events information should be redirected for logging. The information written to this file is similar to the output of -verbose:gc with the time elapsed since the first GC event preceding each logged event. The -Xloggc option overrides -verbose:gc if both are given with the same java command.

来自 Java 版本 8:

-XX:LogFile=path

Sets the path and file name where log data is written. By default, the file is created in the current working directory, and it is named hotspot.log.