jmap 获取内存dump的几种方式

java获取内存dump的几种方式

java获取内存dump的几种方式

获取内存详情：jmap -dump:format=b,file=e.bin pid
这种方式可以用 jvisualvm.exe 进行内存分析，或者采用 Eclipse Memory Analysis Tools (MAT)这个工具

获取内存dump： jmap -histo:live pid
这种方式会先出发fullgc，所有如果不希望触发fullgc 可以使用jmap -histo pid

第三种方式：jdk启动加参数：
-XX:+HeapDumpBeforeFullGC
-XX:HeapDumpPath=/httx/logs/dump
这种方式会产生dump日志，再通过jvisualvm.exe 或者Eclipse Memory Analysis Tools 工具进行分析

jmap 

1）查看堆内存信息，包括使用的GC算法、堆配置参数和各代中堆内存使用情况，可以结合jhat使用

2）主要用于分析OOM

用法：

jmap -heap <PID>

jmap -dump:format=b,file=HeapDump <pid>  #dump出内存信息，可用内存分析工具分析情况，format=b是通过二进制的意思

例如：

[root@lsy-36-70 ~]# jmap -heap 7574
Attaching to process ID 7574, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.211-b12

using thread-local object allocation.
Parallel GC with 8 thread(s)

Heap Configuration:
   MinHeapFreeRatio         = 0
   MaxHeapFreeRatio         = 100
   MaxHeapSize              = 3183476736 (3036.0MB)
   NewSize                  = 66060288 (63.0MB)
   MaxNewSize               = 1061158912 (1012.0MB)
   OldSize                  = 133169152 (127.0MB)
   NewRatio                 = 2
   SurvivorRatio            = 8
   MetaspaceSize            = 21807104 (20.796875MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 17592186044415 MB
   G1HeapRegionSize         = 0 (0.0MB)

Heap Usage:
PS Young Generation
Eden Space:
   capacity = 562561024 (536.5MB)
   used     = 386173616 (368.2838592529297MB)
   free     = 176387408 (168.2161407470703MB)
   68.64564012170172% used
From Space:
   capacity = 1048576 (1.0MB)
   used     = 720896 (0.6875MB)
   free     = 327680 (0.3125MB)
   68.75% used
To Space:
   capacity = 14155776 (13.5MB)
   used     = 0 (0.0MB)
   free     = 14155776 (13.5MB)
   0.0% used
PS Old Generation
   capacity = 108003328 (103.0MB)
   used     = 27321200 (26.055526733398438MB)
   free     = 80682128 (76.94447326660156MB)
   25.296627896503338% used

16408 interned Strings occupying 1561208 bytes.

2）dump出堆内存信息到文件

[root@lsy-36-70 ~]# jmap -dump:format=b,file=/tmp/dump01.dat 7574
Dumping heap to /tmp/dump01.dat ...
Heap dump file created

或者

[root@lsy-36-70 ~]# jmap -dump:format=b,file=/tmp/dump01.dump 7574
Dumping heap to /tmp/dump01.dump ...
Heap dump file created

3）jhat查看，浏览器输入7000端口访问

[root@lsy-36-70 ~]# jhat -port 7000 /tmp/dump01.dat
或者

[root@lsy-36-70 ~]# jhat -port 7000 /tmp/dump01.dump