萎缩的幸存者空间导致持续完整的GC

Question

我使用Tomcat服务器遇到了这种令人不安的经历:

• 我们的哈德森服务器;
• 我们的Web应用程序的暂存版本,每天重新部署5-8次.

问题是我们最终会继续进行垃圾收集,但老一代人却无法填补.我注意到幸存者空间旁边是不存在的,垃圾收集器输出类似于:

[GC 103688K->103688K(3140544K), 0.0226020 secs]
[Full GC 103688K->103677K(3140544K), 1.7742510 secs]
[GC 103677K->103677K(3140544K), 0.0228900 secs]
[Full GC 103677K->103677K(3140544K), 1.7771920 secs]
[GC 103677K->103677K(3143040K), 0.0216210 secs]
[Full GC 103677K->103677K(3143040K), 1.7717220 secs]
[GC 103679K->103677K(3143040K), 0.0219180 secs]
[Full GC 103677K->103677K(3143040K), 1.7685010 secs]
[GC 103677K->103677K(3145408K), 0.0189870 secs]
[Full GC 103677K->103676K(3145408K), 1.7735280 secs]

重启Tomcat之前的堆信息是:

Attaching to process ID 10171, please wait...
Debugger attached successfully.              
Server compiler detected.                    
JVM version is 14.1-b02                      

using thread-local object allocation.
Parallel GC with 8 thread(s)         

Heap Configuration:
   MinHeapFreeRatio = 40
   MaxHeapFreeRatio = 70
   MaxHeapSize      = 3221225472 (3072.0MB)
   NewSize          = 2686976 (2.5625MB)   
   MaxNewSize       = 17592186044415 MB    
   OldSize          = 5439488 (5.1875MB)   
   NewRatio         = 2                    
   SurvivorRatio    = 8                    
   PermSize         = 21757952 (20.75MB)   
   MaxPermSize      = 268435456 (256.0MB)  

Heap Usage:
PS Young Generation
Eden Space:
   capacity = 1073479680 (1023.75MB)
   used     = 0 (0.0MB)
   free     = 1073479680 (1023.75MB)
   0.0% used
From Space:
   capacity = 131072 (0.125MB)
   used     = 0 (0.0MB)
   free     = 131072 (0.125MB)
   0.0% used
To Space:
   capacity = 131072 (0.125MB)
   used     = 0 (0.0MB)
   free     = 131072 (0.125MB)
   0.0% used
PS Old Generation
   capacity = 2147483648 (2048.0MB)
   used     = 106164824 (101.24666595458984MB)
   free     = 2041318824 (1946.7533340454102MB)
   4.943684861063957% used
PS Perm Generation
   capacity = 268435456 (256.0MB)
   used     = 268435272 (255.99982452392578MB)
   free     = 184 (1.7547607421875E-4MB)
   99.99993145465851% used

传递给Tomcat的相关JVM标志是:

-verbose:gc -Dsun.rmi.dgc.client.gcInterval=0x7FFFFFFFFFFFFFFE -Xmx3g -XX:MaxPermSize=256m

请注意,幸存者空间在启动时的大小约为40 MB.

关于如何避免这个问题的任何想法将不胜感激.

---

更新:

JVM版本是

$ java -version
java version "1.6.0_15"
Java(TM) SE Runtime Environment (build 1.6.0_15-b03)
Java HotSpot(TM) 64-Bit Server VM (build 14.1-b02, mixed mode)

我将调查PermGen大小,看看是否有帮助 - 可能是幸存者空间的大小是无关的.

Answer 1

密钥可能PS Perm Generation是99.999%(256***MB中只有184 个字节***免费).

通常,我建议你给它更多的烫发,但你已经给它256MB这应该是充足的.我的猜测是你在某些代码生成库中有内存泄漏.Perm Gen主要用于类的字节码.

Answer 2

这是很容易有ClassLoader的泄漏 - 所有它需要的是通过类装入器装入一个单一的对象不通过它加载的对象被提及.经常重新部署的应用程序将很快填补PermGenSpace.

本文介绍了要注意的内容,后续内容介绍了如何诊断和修复问题.