java-jvm-jhat 博客分类： java-jvm&性能&原理

功能：可以分析jmap dump下的hprof文件

一般配合

 

 jmap -dump:format=b,file=dumpFileName pid

或者

jmap -histo:live 21711 | more

 

jmap -histo:live 21711 | more

 num     #instances         #bytes  class name
----------------------------------------------
   1:         38445        5597736  <constMethodKlass>
   2:         38445        5237288  <methodKlass>
   3:          3500        3749504  <constantPoolKlass>
   4:         60858        3242600  <symbolKlass>
   5:          3500        2715264  <instanceKlassKlass>
   6:          2796        2131424  <constantPoolCacheKlass>
   7:          5543        1317400  [I
   8:         13714        1010768  [C
   9:          4752        1003344  [B
  10:          1225         639656  <methodDataKlass>
  11:         14194         454208  java.lang.String
  12:          3809         396136  java.lang.Class
  13:          4979         311952  [S
  14:          5598         287064  [[I
  15:          3028         266464  java.lang.reflect.Method
  16:           280         163520  <objArrayKlassKlass>
  17:          4355         139360  java.util.HashMap$Entry
  18:          1869         138568  [Ljava.util.HashMap$Entry;
  19:          2443          97720  java.util.LinkedHashMap$Entry
  20:          2072          82880  java.lang.ref.SoftReference
  21:          1807          71528  [Ljava.lang.Object;
  22:          2206          70592  java.lang.ref.WeakReference
  23:           934          52304  java.util.LinkedHashMap
  24:           871          48776  java.beans.MethodDescriptor
  25:          1442          46144  java.util.concurrent.ConcurrentHashMap$HashEntry
  26:           804          38592  java.util.HashMap
  27:           948          37920  java.util.concurrent.ConcurrentHashMap$Segment
  28:          1621          35696  [Ljava.lang.Class;
  29:          1313          34880  [Ljava.lang.String;
  30:          1396          33504  java.util.LinkedList$Entry
  31:           462          33264  java.lang.reflect.Field
  32:          1024          32768  java.util.Hashtable$Entry
  33:           948          31440  [Ljava.util.concurrent.ConcurrentHashMap$HashEntry;

  

 class name是对象类型，说明如下：

B  byte
C  char
D  double
F  float
I  int
J  long
Z  boolean
[  数组，如[I表示int[]
[L+类名 其他对象

 

命令：

jhat  -J-Xmx1024m  D:\myProject\project\httpclientTest\java_pid4652.hprof

输出：

C:\Users\xinchun.wang>jhat  -J-Xmx1024m  D:\myProject\project\httpclientTest\java_pid4652.hprof
Reading from D:\myProject\project\httpclientTest\java_pid4652.hprof...
Dump file created Sun May 14 19:22:48 CST 2017
Snapshot read, resolving...
Resolving 818455 objects...
Chasing references, expect 163 dots.................................................................................................
Eliminating duplicate references....................................................................................................
Snapshot resolved.
Started HTTP server on port 7000
Server is ready.

 

 

浏览器输入：http://127.0.0.1:7000/

 

展示：

All Classes (excluding platform)

Package <Default Package>

class Test [0xff392c48]
class Test$OOMObject [0xff392bd8]
Other Queries

All classes including platform
Show all members of the rootset
Show instance counts for all classes (including platform)
Show instance counts for all classes (excluding platform)
Show heap histogram
Show finalizer summary
Execute Object Query Language (OQL) query