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在没有任何GC活动的情况下清理了JVM内存

[英]JVM memory cleaned up without any GC activity

原文 2014-10-17 11:38:29 1 1 java/ groovy/ garbage-collection/ permgen

I am currently running a long running JVM application (that includes groovy classes), and I have observed some strange behaviour. 我目前正在运行一个运行时间很长的JVM应用程序（包括groovy类），我观察到了一些奇怪的行为。

I run the application and update my Groovy classes (correctly cleaning up metaclass info etc - I know there isn't a leak) so I know there are several classes that could be collected from permgen (normally I observe that permgen isn't collected eagerly - i believe it is just full GC that collects permgen, so not unusual for this state). 我运行应用程序并更新我的Groovy类（正确清理元类信息等 - 我知道没有泄漏）所以我知道有几个类可以从permgen收集（通常我观察到permgen不是急切地收集 - 我相信只有完整的GC才能收集permgen，所以这个状态并不罕见）。 The oddity is that if I leave the application running with no activity, after about an hour or so there is a sudden drop in memory usage (heap and permgen, but most pronounced in permgen), but visualvm reports no GC/CPU activity has happened. 奇怪的是，如果我让应用程序在没有活动的情况下运行，大约一个小时左右后内存使用量会突然下降（堆和permgen，但最明显的是permgen），但visualvm报告没有发生GC / CPU活动。

Below is the screenshot of my visualvm logging 下面是我的visualvm日志记录的截图

在此输入图像描述

My question is how is there such a big drop (~80mb) in permgen with no registered GC activity? 我的问题是，在没有注册GC活动的情况下，permgen有如此大的下降（~80mb）？ visualvm does normally log GC/CPU activity pretty well. visualvm通常可以很好地记录GC / CPU活动。

1 个解决方案

Try to install visualgc plugin, to investigate how gc work in this situation. 尝试安装visualgc插件，以调查gc在这种情况下的工作方式。 I guess a lot of new generation object was dropped, but I can't told it by screenshot. 我想很多新一代对象都被删除了，但是我无法通过截图告诉它。