問題描述

最近同事系統反饋系統出現如下錯誤：

PermGen space的全稱是Permanent Generation space,是指記憶體的永久儲存區域。

解決過程

使用jstat檢視 Permsize 佔用情況，如下所示：

using thread-local object allocation.
Parallel GC with 4 thread(s)

Heap Configuration:
   MinHeapFreeRatio = 40
   MaxHeapFreeRatio = 70
   MaxHeapSize      = 2147483648 (2048.0MB)
   NewSize          = 1310720
 
 (1.25MB)
   MaxNewSize       = 17592186044415 MB
   OldSize          = 5439488 (5.1875MB)
   NewRatio         = 2
   SurvivorRatio    = 8
   PermSize         = 21757952 (20.75MB)
   MaxPermSize      = 85983232 (82.0MB)

Heap Usage:
PS Young Generation
Eden Space:
   capacity = 715259904 (682.125MB)
   used     = 8176712
 
 (7.797920227050781MB)
   free     = 707083192 (674.3270797729492MB)
   1.1431805353931876% used
From Space:
   capacity = 262144 (0.25MB)
   used     = 0 (0.0MB)
   free     = 262144 (0.25MB)
   0.0% used
To Space:
   capacity = 262144 (0.25MB)
   used     = 0 (0.0MB)
   free     = 262144 (0.25MB)
   0.0% used
PS Old Generation
   capacity = 1431699456
 
 (1365.375MB)
   used     = 45577208 (43.46581268310547MB)
   free     = 1386122248 (1321.9091873168945MB)
   3.183434051678511% used
PS Perm Generation
   capacity = 85983232 (82.0MB)
   used     = 85982928 (81.99971008300781MB)
   free     = 304 (2.899169921875E-4MB)
   99.99964644269245% used

如上所示，可以看到PS Perm Generation被佔用了99%，分配不足。

解決方案

從上面 可以看出MaxPermSize = 85983232 (82.0MB)即永久儲存區域擴大設定
如：
對於Tomcat伺服器，則需要修改TOMCAT_HOME/bin/catalina.sh
SET JAVA_OPTS=-XX：PermSize=64 M -XX：MaxPermSize=256 M