jmap

输出进程、核心文件或远程调试服务器的共享对象内存或者堆内存的相关信息。

语法

jmap [ options ] pid
jmap [ options ] executable core
jmap [ options ] [ pid ] server-id@ ] remote-hostname-or-IP

解释

executable

产生核心转储的Java可执行文件
core

打印内存信息的核心文件
remote-hostname-or-IP

远程调试服务器的hostname或者IP地址。查看jsadebug
server-id

远程服务器上有多个调试服务器时，提供的调式服务器唯一ID
通过``-J-d64可以指定jmap`运行在64位JVM上

jmap -J-d64 -heap pid

Options

`<no option>`

没有option参数，jmap命令输出共享对象映射信息。会输出JVM中所有共享对象的起始地址、映射大小、文件的全路径

$ jmap 5208
Attaching to process ID 5208, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.40-b25
0x0000000056140000      8716K   D:\path\Java\java1.8\64_jdk1.8.0_40\jre\bin\server\jvm.dll
0x00000000569d0000      840K    D:\path\Java\java1.8\64_jdk1.8.0_40\jre\bin\msvcr100.dll
0x0000000056e10000      52K     D:\path\Java\java1.8\64_jdk1.8.0_40\jre\bin\management.dll
0x0000000056e20000      68K     D:\path\Java\java1.8\64_jdk1.8.0_40\jre\bin\nio.dll
0x0000000056e40000      104K    D:\path\Java\java1.8\64_jdk1.8.0_40\jre\bin\net.dll
0x0000000056e60000      88K     D:\path\Java\java1.8\64_jdk1.8.0_40\jre\bin\zip.dll

`-dump:[live,] format=b, file=filename`

将Java堆信息存入filename指定文件名的hprof二进制文件中；
live 是可选操作，指定live表示只保存活跃对象；
使用jhat命令可以读取文件；

$ jmap -dump:live,format=b,file=test 5208
Dumping heap to C:\user\username\Desktop\test ...
Heap dump file created

$ jhat  C:\\Users\\username\\Desktop\\test
Reading from C:\Users\username\Desktop\test...
Dump file created Fri Dec 27 13:20:01 CST 2019
Snapshot read, resolving...
Resolving 502739 objects...
Chasing references, expect 100 dots....................................................................................................
Eliminating duplicate references....................................................................................................
Snapshot resolved.
Started HTTP server on port 7000
Server is ready.

访问localhost:7000可以查看文件具体内容

`finalizerinfo`

$ jmap -finalizerinfo 10864
Attaching to process ID 10864, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.40-b25
Number of objects pending for finalization: 0

`heap`

输出堆垃圾回收的摘要信息，配置信息，各年代的堆使用信息以及 interned Strings的是数量和大小。

$ jmap -heap 10864
Attaching to process ID 10864, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.40-b25

using thread-local object allocation.
Garbage-First (G1) GC with 4 thread(s)

Heap Configuration:
   MinHeapFreeRatio         = 40
   MaxHeapFreeRatio         = 70
   MaxHeapSize              = 1073741824 (1024.0MB)
   NewSize                  = 1363144 (1.2999954223632812MB)
   MaxNewSize               = 643825664 (614.0MB)
   OldSize                  = 5452592 (5.1999969482421875MB)
   NewRatio                 = 2
   SurvivorRatio            = 8
   MetaspaceSize            = 21807104 (20.796875MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 268435456 (256.0MB)
   G1HeapRegionSize         = 1048576 (1.0MB)

Heap Usage:
G1 Heap:
   regions  = 1024
   capacity = 1073741824 (1024.0MB)
   used     = 402117216 (383.4888610839844MB)
   free     = 671624608 (640.5111389160156MB)
   37.45008409023285% used
G1 Young Generation:
Eden Space:
   regions  = 341
   capacity = 572522496 (546.0MB)
   used     = 357564416 (341.0MB)
   free     = 214958080 (205.0MB)
   62.45421245421245% used
Survivor Space:
   regions  = 31
   capacity = 32505856 (31.0MB)
   used     = 32505856 (31.0MB)
   free     = 0 (0.0MB)
   100.0% used
G1 Old Generation:
   regions  = 15
   capacity = 468713472 (447.0MB)
   used     = 10998368 (10.488861083984375MB)
   free     = 457715104 (436.5111389160156MB)
   2.34650136107033% used

22533 interned Strings occupying 2048048 bytes.

`histo[:live]`

将堆信息以列表（histogram）的形式输出；
输出每个类的信息：对象个数、内存字节数、全路径；
如果指定live，只统计活跃对象信息（从以下输出可以看到对象数是不同的）

$ jmap -histo 10864

 num     #instances         #bytes  class name
----------------------------------------------
   1:        887212      198868312  [C
   2:        423381       89093320  [B
   3:         46645       26477944  [I
   4:        542764       13026336  java.lang.String
   5:        128620       12347520  sun.util.calendar.Gregorian$Date
   6:        128391       10271280  java.util.zip.ZipEntry
   7:         92913        4668984  [Ljava.lang.Object;
   8:        112727        2705448  java.util.Date
   9:         46899        2626344  java.util.stream.ReferencePipeline$Head
  10:         48749        1949960  java.security.AccessControlContext
  11:         82135        1814832  [Ljava.lang.Class;
  12:         14411        1632616  java.lang.Class
  13:         50674        1621568  java.util.HashMap$Node
  14:         46875        1500000  java.util.Spliterators$ArraySpliterator
  15:         16237        1314488  [Ljava.util.HashMap$Node;
  16:         14048        1236224  java.lang.reflect.Method
  17:         35411        1133152  java.util.concurrent.ConcurrentHashMap$Node
  18:         46864        1124736  java.util.stream.MatchOps$$Lambda$45/319558327
  19:         40542         973008  java.lang.StringBuilder
  20:         19482         935136  java.util.HashMap
  21:         26831         870296  [Ljava.security.ProtectionDomain;
  22:         33581         805944  org.apache.commons.collections.map.ListOrderedMap$ListOrderedMapEntry
  23:          9684         772896  [S
  24:         46864         749824  org.apache.jorphan.reflect.ClassFinder$ExtendsClassFilter$$Lambda$44/1397381784
  25:         20407         653024  java.util.ArrayList$Itr
  26:         10000         640000  java.awt.event.InvocationEvent
  27:         18944         606208  java.util.concurrent.locks.AbstractQueuedSynchronizer$Node
  28:         18127         580064  java.util.Hashtable$Entry
  29:         17336         554752  java.beans.PropertyChangeEvent
  30:         13686         547440  java.lang.ref.Finalizer
  31:         31829         509264  java.lang.Object
  32:         19459         467016  java.util.ArrayList
....................
3770:             1             16  sun.text.normalizer.NormalizerImpl$FCDTrieImpl
3771:             1             16  sun.text.normalizer.NormalizerImpl$NormTrieImpl
3772:             1             16  sun.util.CoreResourceBundleControl
3773:             1             16  sun.util.calendar.Gregorian
3774:             1             16  sun.util.locale.InternalLocaleBuilder$CaseInsensitiveChar
3775:             1             16  sun.util.locale.provider.AuxLocaleProviderAdapter$NullProvider
3776:             1             16  sun.util.locale.provider.CalendarDataUtility$CalendarFieldValueNamesMapGetter
3777:             1             16  sun.util.locale.provider.CalendarDataUtility$CalendarWeekParameterGetter
3778:             1             16  sun.util.locale.provider.CalendarNameProviderImpl$LengthBasedComparator
3779:             1             16  sun.util.locale.provider.SPILocaleProviderAdapter
3780:             1             16  sun.util.locale.provider.TimeZoneNameUtility$TimeZoneNameGetter
3781:             1             16  sun.util.resources.LocaleData
3782:             1             16  sun.util.resources.LocaleData$LocaleDataResourceBundleControl
Total       3659918      405059648

$ jmap -histo:live 10864

 num     #instances         #bytes  class name
----------------------------------------------
   1:          7681        6404584  [B
   2:         74426        6304912  [C
   3:         13259        4714608  [I
   4:         72674        1744176  java.lang.String
   5:         14411        1632616  java.lang.Class
   ......................
   3034:             1             16  sun.util.locale.provider.SPILocaleProviderAdapter
3035:             1             16  sun.util.locale.provider.TimeZoneNameUtility$TimeZoneNameGetter
3036:             1             16  sun.util.resources.LocaleData
3037:             1             16  sun.util.resources.LocaleData$LocaleDataResourceBundleControl
Total        561269       36751776

`clstats`

输出Java堆中类加载器的统计信息；
输出每个类加载器的信息：名称，状态，地址，父类加载器，已加载的类的数量和大小；
统计会比较耗费时间；

$ jmap -clstats 10864
Attaching to process ID 10864, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.40-b25
finding class loader instances ..done.
computing per loader stat ..done.
please wait.. computing liveness..........................................................liveness analysis may be inaccurate ...
class_loader    classes bytes   parent_loader   alive?  type

<bootstrap>     3835    6981748   null          live    <internal>
0x00000000c02ccba8      1       1471    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c1aa4420      1       878     0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c02cd820      1       1472    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c202e190      1       878       null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c1c3e350      1       878       null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c1dbe048      1       1472    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c02ccd38      1       1472    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c134d6a0      1       1471    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c03acea0      1       1471      null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c02cc7b0      10587   13944043        0x00000000c0300be8      live    org/apache/jmeter/DynamicClassLoader@0x0000000100060218
0x00000000c1e0fe40      1       878     0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c10256a0      1       1471    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c02cc888      1       1481      null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c19dc138      1       1471      null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c19dcb38      1       1473      null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c19e6fb8      1       1473      null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c19aa9b0      1       1473      null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c1aa5000      1       878       null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c02cce00      1       1472      null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c0fd55d0      12      37189   0x00000000c0300be8      live    sun/reflect/misc/MethodUtil@0x00000001001e1028
0x00000000c0ef5fc0      1       878       null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c02cca18      1       1472    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c0270990      0       0       0x00000000c0300be8      live    java/util/ResourceBundle$RBClassLoader@0x00000001000f2f58
0x00000000c0fd4ec0      1       878     0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c0ef6450      1       1471    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c1025440      1       878       null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c02cd8e8      1       1472    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c037f870      1       1471    0x00000000c02ccec8      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c1eac520      1       878       null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c1fb10b0      1       878     0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c02ccae0      1       1472    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c03d5370      1       878       null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c10a22d8      1       1471      null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c23a9668      1       878       null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c0300be8      37      144387  0x00000000c02ccec8      live    sun/misc/Launcher$AppClassLoader@0x000000010000f668
0x00000000c02ccc70      1       1471    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c13df1e0      1       1472      null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c1522db0      1       1471      null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c202e8e0      1       878       null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c02ccec8      152     345291    null          live    sun/misc/Launcher$ExtClassLoader@0x000000010000fa10
0x00000000c20611e0      1       1471    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c0ef6108      1       878       null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c19e2e70      1       1473      null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c1fe6910      1       878     0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c206a068      1       878     0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c10a1ef8      1       878       null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c0fd5088      1       889     0x00000000c0fd55d0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c13d75c8      1       1473      null          dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c1e25298      1       1471    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c02cc950      1       1471    0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8
0x00000000c23c42c0      1       878     0x00000000c02cc7b0      dead    sun/reflect/DelegatingClassLoader@0x0000000100009df8

total = 52      14669   21509096            N/A         alive=6, dead=46            N/A

`F`

强制输出

使用jmap -dump或者jmap -histo命令时，如果进程没有响应，可以使用-F强制输出；
live模式下不能使用-F强制输出；

`h` `help`

-h与-help都是输出帮助信息的指令

-Jflag

将flag信息传递给运行jamp命令的虚拟机

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Java自带故障分析工具jmap工具使用说明

Java自带故障分析工具jmap工具使用说明

jmap

语法

解释

Options

`<no option>`

`-dump:[live,] format=b, file=filename`

`finalizerinfo`

`heap`

`histo[:live]`

`clstats`

`F`

`h` `help`

-Jflag

其他文章列表

Java自带故障分析工具jmap工具使用说明

jmap

语法

解释

Options

<no option>

-dump:[live,] format=b, file=*filename*

finalizerinfo

heap

histo[:live]

clstats

F

h help

-Jflag

其他文章列表

`<no option>`

`-dump:[live,] format=b, file=filename`

`finalizerinfo`

`heap`

`histo[:live]`

`clstats`

`F`

`h` `help`