jmap

jmap

此命令用来查看内存信息，实例个数以及占用内存大小

jmap

jmap -histo -F  27515 >  ./log.txt

查看堆信息

jmap -heap 进程Id

Attaching to process ID 27515, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.201-b09

using parallel threads in the new generation.
using thread-local object allocation.
Concurrent Mark-Sweep GC

Heap Configuration:
   MinHeapFreeRatio         = 40
   MaxHeapFreeRatio         = 70
   MaxHeapSize              = 536870912 (512.0MB)
   NewSize                  = 178913280 (170.625MB)
   MaxNewSize               = 178913280 (170.625MB)
   OldSize                  = 89522176 (85.375MB)
   NewRatio                 = 2
   SurvivorRatio            = 2
   MetaspaceSize            = 21807104 (20.796875MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 17592186044415 MB
   G1HeapRegionSize         = 0 (0.0MB)

Heap Usage:
New Generation (Eden + 1 Survivor Space):
   capacity = 134217728 (128.0MB)
   used     = 17779880 (16.956214904785156MB)
   free     = 116437848 (111.04378509521484MB)
   13.247042894363403% used
Eden Space:
   capacity = 89522176 (85.375MB)
   used     = 9343864 (8.911003112792969MB)
   free     = 80178312 (76.46399688720703MB)
   10.437485344413433% used
From Space:
   capacity = 44695552 (42.625MB)
   used     = 8436016 (8.045211791992188MB)
   free     = 36259536 (34.57978820800781MB)
   18.874397165964076% used
To Space:
   capacity = 44695552 (42.625MB)
   used     = 0 (0.0MB)
   free     = 44695552 (42.625MB)
   0.0% used
concurrent mark-sweep generation:
   capacity = 201170944 (191.8515625MB)
   used     = 128766432 (122.80123901367188MB)
   free     = 72404512 (69.05032348632812MB)
   64.0084643635216% used

　　

堆内存dump

jmap -dump:format=b,file=xxx.hprof  进程Id