D:\Users\yftan>jmap -heap 7872
Attaching to process ID 7872, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.45-b08
using thread-local object allocation.
Parallel GC with 4 thread(s)
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 2076180480 (1980.0MB)
NewSize = 1310720 (1.25MB)
MaxNewSize = 17592186044415 MB
OldSize = 5439488 (5.1875MB)
NewRatio = 2
SurvivorRatio = 8
PermSize = 21757952 (20.75MB)
MaxPermSize = 85983232 (82.0MB)
G1HeapRegionSize = 0 (0.0MB)
Heap Usage:
PS Young Generation
Eden Space:
capacity = 691011584 (659.0MB)
used = 0 (0.0MB)
free = 691011584 (659.0MB)
0.0% used
From Space:
capacity = 524288 (0.5MB)
used = 0 (0.0MB)
free = 524288 (0.5MB)
0.0% used
To Space:
capacity = 524288 (0.5MB)
used = 0 (0.0MB)
free = 524288 (0.5MB)
0.0% used
PS Old Generation
capacity = 1384120320 (1320.0MB)
used = 80359816 (76.63709259033203MB)
free = 1303760504 (1243.362907409668MB)
5.805840347752427% used
PS Perm Generation
capacity = 85983232 (82.0MB)
used = 85983224 (81.99999237060547MB)
free = 8 (7.62939453125E-6MB)
99.99999069586033% used
32533 interned Strings occupying 4048688 bytes.
从上可见由于没有设置PermSize ，导致Perm 内存移除了，并且，Perm 区和Old 区都在heap中