使用jmap

使用jmap观察调整的效果：
cd /opt/jdk/bin
./jmap -heap 9657
Attaching to process ID 9657, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 1.5.0_07-b03

using thread-local object allocation.
Mark Sweep Compact GC

Heap Configuration:
   MinHeapFreeRatio = 40
   MaxHeapFreeRatio = 70
   MaxHeapSize      = 964689920 (920.0MB)
   NewSize          = 655360 (0.625MB)
   MaxNewSize       = 4294901760 (4095.9375MB)
   OldSize          = 1441792 (1.375MB)
   NewRatio         = 8
   SurvivorRatio    = 8
   PermSize         = 67108864 (64.0MB)
   MaxPermSize      = 134217728 (128.0MB)

Heap Usage:
New Generation (Eden + 1 Survivor Space):
   capacity = 96468992 (92.0MB)
   used     = 4733136 (4.5138702392578125MB)
   free     = 91735856 (87.48612976074219MB)
   4.906380694845448% used
Eden Space:
   capacity = 85786624 (81.8125MB)
   used     = 4733136 (4.5138702392578125MB)
   free     = 81053488 (77.29862976074219MB)
   5.517335662958365% used
From Space:
   capacity = 10682368 (10.1875MB)
   used     = 0 (0.0MB)
   free     = 10682368 (10.1875MB)
   0.0% used
To Space:
   capacity = 10682368 (10.1875MB)
   used     = 0 (0.0MB)
   free     = 10682368 (10.1875MB)
   0.0% used
tenured generation:
   capacity = 857538560 (817.8125MB)
   used     = 193104168 (184.15848541259766MB)
   free     = 664434392 (633.6540145874023MB)
   22.51842389454767% used
Perm Generation:
   capacity = 67108864 (64.0MB)
   used     = 45904968 (43.77838897705078MB)
   free     = 21203896 (20.22161102294922MB)
   68.40373277664185% used