Tomcat内存分析相关方法(jmap和mat)

Linux环境命令行

首先，根据进程命令，获取运行的tomcat的进程ID

ps aux | grep tomcat | grep java | grep bsc

ps aux | grep tomcat | grep java | grep bsc
 

在第二列可以看到进程ID

然后使用jmap可以查看内存占比：

/home/work/bsc/java/jdk-1.7-7u60/bin/jmap -heap 7840

/ home / work / bsc / java / jdk - 1.7 - 7u60 / bin / jmap - heap 7840
 

输出的结果包括了内存各个部分的占比：

[work@xxxx.com logs]$ /home/work/bsc/java/jdk-1.7-7u60/bin/jmap -heap 10433 Attaching to process ID 10433, please wait... Debugger attached successfully. Server compiler detected. JVM version is 24.60-b09 using parallel threads in the new generation. using thread-local object allocation. Concurrent Mark-Sweep GC Heap Configuration: MinHeapFreeRatio = 40 MaxHeapFreeRatio = 70 MaxHeapSize = 8388608000 (8000.0MB) NewSize = 1048576000 (1000.0MB) MaxNewSize = 1048576000 (1000.0MB) OldSize = 5439488 (5.1875MB) NewRatio = 2 SurvivorRatio = 8 PermSize = 134217728 (128.0MB) MaxPermSize = 268435456 (256.0MB) G1HeapRegionSize = 0 (0.0MB) Heap Usage: New Generation (Eden + 1 Survivor Space): capacity = 943718400 (900.0MB) used = 393328672 (375.1074523925781MB) free = 550389728 (524.8925476074219MB) 41.67860582139757% used Eden Space: capacity = 838860800 (800.0MB) used = 288471072 (275.1074523925781MB) free = 550389728 (524.8925476074219MB) 34.388431549072266% used From Space: capacity = 104857600 (100.0MB) used = 104857600 (100.0MB) free = 0 (0.0MB) 100.0% used To Space: capacity = 104857600 (100.0MB) used = 0 (0.0MB) free = 104857600 (100.0MB) 0.0% used concurrent mark-sweep generation: capacity = 1288736768 (1229.03515625MB) used = 706435104 (673.7090148925781MB) free = 582301664 (555.3261413574219MB) 54.816089797478334% used Perm Generation: capacity = 134217728 (128.0MB) used = 65034240 (62.021484375MB) free = 69183488 (65.978515625MB) 48.45428466796875% used 27139 interned Strings occupying 3055832 bytes.

[ work @ xxxx . com logs ] $ / home / work / bsc / java / jdk - 1.7 - 7u60 / bin / jmap - heap 10433
Attaching to process ID 10433 , please wait . . .
Debugger attached successfully .
Server compiler detected .
JVM version is 24.60 - b09
 
using parallel threads in the new generation .
using thread - local object allocation .
Concurrent Mark - Sweep GC
 
Heap Configuration :
   MinHeapFreeRatio = 40
   MaxHeapFreeRatio = 70
   MaxHeapSize        = 8388608000 ( 8000.0MB )
   NewSize            = 1048576000 ( 1000.0MB )
   MaxNewSize        = 1048576000 ( 1000.0MB )
   OldSize            = 5439488 ( 5.1875MB )
   NewRatio          = 2
   SurvivorRatio      = 8
   PermSize          = 134217728 ( 128.0MB )
   MaxPermSize        = 268435456 ( 256.0MB )
   G1HeapRegionSize = 0 ( 0.0MB )
 
Heap Usage :
New Generation ( Eden + 1 Survivor Space ) :
   capacity = 943718400 ( 900.0MB )
   used      = 393328672 ( 375.1074523925781MB )
   free      = 550389728 ( 524.8925476074219MB )
   41.67860582139757 % used
Eden Space :
   capacity = 838860800 ( 800.0MB )
   used      = 288471072 ( 275.1074523925781MB )
   free      = 550389728 ( 524.8925476074219MB )
   34.388431549072266 % used
From Space :
   capacity = 104857600 ( 100.0MB )
   used      = 104857600 ( 100.0MB )
   free      = 0 ( 0.0MB )
   100.0 % used
To Space :
   capacity = 104857600 ( 100.0MB )
   used      = 0 ( 0.0MB )
   free      = 104857600 ( 100.0MB )
   0.0 % used
concurrent mark - sweep generation :
   capacity = 1288736768 ( 1229.03515625MB )
   used      = 706435104 ( 673.7090148925781MB )
   free      = 582301664 ( 555.3261413574219MB )
   54.816089797478334 % used
Perm Generation :
   capacity = 134217728 ( 128.0MB )
   used      = 65034240 ( 62.021484375MB )
   free      = 69183488 ( 65.978515625MB )
   48.45428466796875 % used
 
27139 interned Strings occupying 3055832 bytes .
 

如上可以清楚的看到内存配置信息、年轻代（包括eden、from、to）、老年代、永久代各自的内存信息和占比。

使用Eclipse的memory analysis tool工具进行详细分析

首先，使用命令将内存dump到文件：

/home/work/bsc/java/jdk-1.7-7u60/bin/jmap -dump:format=b,file=/home/work/tmp/bsc.bin 10433

/ home / work / bsc / java / jdk - 1.7 - 7u60 / bin / jmap - dump : format = b , file = / home / work / tmp / bsc . bin 10433
 

MAT(Memory Analyzer Tool)工具是eclipse的一个插件，使用起来非常方便，尤其是在分析大内存的dump文件时，可以非常直观的看到各个对象在堆空间中所占用的内存大小、类实例数量、对象引用关系、利用OQL对象查询，以及可以很方便的找出对象GC Roots的相关信息，当然最吸引人的还是能够快速为开发人员生成内存泄露报表，方便定位问题和分析问题。

MAT工具的下载地址为： http://www.eclipse.org/mat/downloads.php

MAT插件的下载地址为： http://download.eclipse.org/mat/1.3/update-site/

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然后就可以查看内存中的数据，点击饼图，也可以看下占比最大的对象是什么，从而分析程序的行为。