JVM内存状况查看方法和分析工具-jmap

jmap -heap 27657 

Attaching to process ID 27657, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.51-b03

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

Heap Configuration:
   MinHeapFreeRatio = 40
   MaxHeapFreeRatio = 70
   MaxHeapSize      = 536870912 (512.0MB)
   NewSize          = 1048576 (1.0MB)
   MaxNewSize       = 4294901760 (4095.9375MB)
   OldSize          = 4194304 (4.0MB)
   NewRatio         = 2
   SurvivorRatio    = 8
   PermSize         = 16777216 (16.0MB)
   MaxPermSize      = 67108864 (64.0MB)
   G1HeapRegionSize = 0 (0.0MB)

Heap Usage:
PS Young Generation
Eden Space:
   capacity = 11010048 (10.5MB)
   used     = 9314392 (8.882896423339844MB)
   free     = 1695656 (1.6171035766601562MB)
   84.59901355561756% 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 = 40894464 (39.0MB)
   used     = 34679464 (33.072914123535156MB)
   free     = 6215000 (5.927085876464844MB)
   84.8023439065004% used
PS Perm Generation
   capacity = 17301504 (16.5MB)
   used     = 17055496 (16.26538848876953MB)
   free     = 246008 (0.23461151123046875MB)
   98.57811205314867% used

9300 interned Strings occupying 768008 bytes.