jvm实战

11:45 [[email protected]]$ jstat -class 24837              
Loaded  Bytes  Unloaded  Bytes     Time   
  4779 10066.7        0     0.0       3.54
tty:[0] jobs:[0] cwd:[~]
11:45 [[email protected]]$ jinfo -flag MaxPermSize 24837          
-XX:MaxPermSize=536870912

11:57 [[email protected]]$ jmap -dump:format=b,file=jmapformat.txt 24837
Dumping heap to /home/cafe/jmapformat.txt ...
Heap dump file created
tty:[0] jobs:[0] cwd:[~]
12:00 [[email protected]]$ more jmapformat.txt 
JAVA PROFILE 1.0.1kson/map/JsonSerializer;)VoyObjectteInsertRowWithDefaultValues/springframework/core/ResolvableType; switch to standist<Lorg/apache/zookeeper/ClientCnxn$Packet;>;Z)Lorg/apache/zookeeper/ClientCnxn$Packet;ject;>;ng/Class<*>;Ljava/lang/Class<*>;)Vr;ema-typeing$Entry;)IData;peSQLring;Ljava/io/File;)Ljava/lang/Process;
mer Time
Lorg/apache/zookeeper/proto/RequestHeader;Lorg/apache/zookeeper/proto/ReplyHeader;Lorg/apache/jute/Record;Lorg/apache/jute/Record;Lorg/apa
che/zookeeper/AsyncCallback;Ljava/lang/String;Ljava/lang/String;Ljava/lang/Object;Lorg/apache/zookeeper/ZooKeeper$WatchRegistration;)Lorg/
am;)V/zookeeper/ClientCnxn$Packet;--More--(0%)
ar:' URL: (0%)teArrayPropertyEditor--More--(0%)

e.org/xml/properties/rties: --More--(0%)Object;JJ)Ljava/util/Set;--More--(0%)
/jackson/map/ser/std/SerializerBase<TT;>;/management/ObjectName$Property;>;II)V--More--(0%)
TMLManagerServlet$7%)rvlet$4--More--(0%)ersers/XSDSimpleTypeTraverser;--More--(0%)

jmap -dump:live,format=b,file=heap.txt 24837
jmap -dump:format=b,file=jmapformat.txt 24837

12:20 [[email protected]]$ jhat heap.txt
Reading from heap.txt...
Dump file created Tue Jan 12 12:20:18 CST 2016
Snapshot read, resolving...
Resolving 244567 objects...
Chasing references, expect 48 dots................................................
Eliminating duplicate references................................................
Snapshot resolved.
Started HTTP server on port 7000
Server is ready.

1、top
2、shift+H 在终端1，按下“H”键或者“shift+h”，top视图会切换到线程视图，其中PID是线程号
nginx     15   0 269m 29m 924 S 0.7 0.0 133:43.06 nginx
29077 nginx     15   0 269m 28m 872 S 0.3 0.0 134:12.98 nginx                                                                            1 root      15   0 10368 684 572 S 0.0 0.0   0:01.25 init
    2 root      RT -5     0    0    0 S 0.0 0.0   0:10.92 migration/0                                                                      3 root      34 19     0    0    0 S 0.0 0.0   0:00.00 ksoftirqd/0
    4 root      RT -5     0    0    0 S 0.0 0.0   0:00.00 watchdog/0                                                                       5 root      RT -5     0    0    0 S 0.0 0.0   0:12.51 migration/1
    6 root      34 19     0    0    0 S 0.0 0.0   0:00.00 ksoftirqd/1                                                                      7 root      RT -5     0    0    0 S 0.0 0.0   0:00.00 watchdog/1
    8 root      RT -5     0    0    0 S 0.0 0.0   0:03.06 migration/2                                                                      9 root      34 19     0    0    0 S 0.0 0.0   0:00.67 ksoftirqd/2
   10 root      RT -5     0    0    0 S 0.0 0.0   0:00.00 watchdog/2                                                                      11 root      RT -5     0    0    0 S 0.0 0.0   0:02.12 migration/3
   12 root      34 19     0    0    0 S 0.0 0.0   0:01.00 ksoftirqd/3                                                                     13 root      RT -5     0    0    0 S 0.0 0.0   0:00.00 watchdog/3
   14 root      RT -5     0    0    0 S 0.0 0.0   0:01.83 migration/4                                                                     15 root      34 19     0    0    0 S 0.0 0.0   0:00.06 ksoftirqd/4
   16 root      RT -5     0    0    0 S 0.0 0.0   0:00.00 watchdog/4                                                                      17 root      RT -5     0    0    0 S 0.0 0.0   0:00.73 migration/5
   18 root      34 19     0    0    0 S 0.0 0.0   0:00.04 ksoftirqd/5                                                                     19 root      RT -5     0    0    0 S 0.0 0.0   0:00.00 watchdog/5
   20 root      RT -5     0    0    0 S 0.0 0.0   0:01.28 migration/6                                                                     21 root      34 19     0    0    0 S 0.0 0.0   0:00.03 ksoftirqd/6
   22 root      RT -5     0    0    0 S 0.0 0.0   0:00.00 watchdog/6                                                                      23 root      RT -5     0    0    0 S 0.0 0.0   0:00.52 migration/7
   24 root      34 19     0    0    0 S 0.0 0.0   0:00.04 ksoftirqd/7                                                                     25 root      RT -5     0    0    0 S 0.0 0.0   0:00.00 watchdog/7
   26 root      10 -5     0    0    0 S 0.0 0.0   0:01.91 events/0                                                                        27 root      10 -5     0    0    0 S 0.0 0.0   0:49.45 events/1
   28 root      10 -5     0    0    0 S 0.0 0.0   0:04.01 events/2                                                                        29 root      10 -5     0    0    0 S 0.0 0.0   0:00.87 events/3
   30 root      10 -5     0    0    0 S 0.0 0.0   0:01.08 events/4                                                                        31 root      10 -5     0    0    0 S 0.0 0.0   0:00.06 events/5
tty:[1] jobs:[0] cwd:[/opt/logs/nginx/access]

需要将top命令展示的线程号转换为16进制，以15100为例，在linux下输入命令：printf 0x%x 15100，得到15100的十六进制为0x3afc

13:25 [[email protected]]$ printf 0x%x 27698
0x6c32

jstack 27698 > jstack27698.txt

与nid一致即找到

使用top -H -p PID 命令查看对应进程是哪个线程占用CPU过高

top - 13:31:47 up 252 days, 2:51, 1 user, load average: 0.07, 0.10, 0.09
Tasks: 68 total,   0 running, 68 sleeping,   0 stopped,   0 zombie
Cpu(s): 0.3%us, 0.1%sy, 0.0%ni, 99.3%id, 0.2%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 65995412k total, 39238540k used, 26756872k free,   208128k buffers
Swap: 4192956k total,        0k used, 4192956k free, 36363388k cached

PID USER      PR NI VIRT RES SHR S %CPU %MEM    TIME+ COMMAND
27698 cafe      18   0 5050m 287m 10m S 0.0 0.4   0:00.00 java
27701 cafe      18   0 5050m 287m 10m S 0.0 0.4   0:06.00 java
27702 cafe      15   0 5050m 287m 10m S 0.0 0.4   0:00.11 java
27703 cafe      15   0 5050m 287m 10m S 0.0 0.4   0:00.09 java
27704 cafe      16   0 5050m 287m 10m S 0.0 0.4   0:00.11 java
27705 cafe      15   0 5050m 287m 10m S 0.0 0.4   0:00.07 java

查看线程信息
13:31 [[email protected]]$ ps -mp 27698 -o THREAD,tid,time
USER     %CPU PRI SCNT WCHAN USER SYSTEM   TID     TIME
cafe      1.4   -    - -         -      -     - 00:00:57
cafe      0.0 21    - futex_    -      - 27698 00:00:00
cafe      0.1 21    - -         -      - 27701 00:00:06
cafe      0.0 24    - futex_    -      - 27702 00:00:00
cafe      0.0 24    - futex_    -      - 27703 00:00:00
cafe      0.0 23    - futex_    -      - 27704 00:00:00
cafe      0.0 24    - 184466    -      - 27705 00:00:00
cafe      0.0 24    - futex_    -      - 27706 00:00:00
cafe      0.0 24    - 184466    -      - 27707 00:00:00
cafe      0.0 24    - 184466    -      - 27708 00:00:00
cafe      0.0 24    - 184466    -      - 27709 00:00:00
cafe      0.0 17    - 184466    -      - 27710 00:00:00
cafe      0.0 20    - futex_    -      - 27711 00:00:00

http://my.oschina.net/jccpp/blog/129784

jmap
打印出某个java进程（使用pid）内存内的，所有‘对象’的情况（如：产生那些对象，及其数量）。

可以输出所有内存中对象的工具，甚至可以将VM 中的heap，以二进制输出成文本。使用方法 jmap -histo pid。如果连用SHELL jmap -histo pid>a.log可以将其保存到文本中去，在一段时间后，使用文本对比工具，可以对比出GC回收了哪些对象。jmap -dump:format=b,file=outfile 3024可以将3024进程的内存heap输出出来到outfile文件里，再配合MAT（内存分析工具(Memory Analysis Tool）或与jhat (Java Heap Analysis Tool)一起使用，能够以图像的形式直观的展示当前内存是否有问题。

64位机上使用需要使用如下方式：

jmap -J-d64 -heap pid

命令格式
       jmap [ option ] pid

       jmap [ option ] executable core

       jmap [ option ] [server-id@]remote-hostname-or-IP

参数说明
1)、options： 

executable Java executable from which the core dump was produced.

(可能是产生core dump的java可执行程序)

core 将被打印信息的core dump文件

remote-hostname-or-IP 远程debug服务的主机名或ip

server-id 唯一id,假如一台主机上多个远程debug服务 

2）、基本参数：

-dump:[live,]format=b,file=<filename> 使用hprof二进制形式,输出jvm的heap内容到文件=. live子选项是可选的，假如指定live选项,那么只输出活的对象到文件. 

-finalizerinfo 打印正等候回收的对象的信息.

-heap 打印heap的概要信息，GC使用的算法，heap的配置及wise heap的使用情况.

-histo[:live] 打印每个class的实例数目,内存占用,类全名信息. VM的内部类名字开头会加上前缀”*”. 如果live子参数加上后,只统计活的对象数量. 

-permstat 打印classload和jvm heap长久层的信息. 包含每个classloader的名字,活泼性,地址,父classloader和加载的class数量. 另外,内部String的数量和占用内存数也会打印出来. 

-F 强迫.在pid没有相应的时候使用-dump或者-histo参数. 在这个模式下,live子参数无效. 

-h | -help 打印辅助信息 

-J 传递参数给jmap启动的jvm. 

pid 需要被打印配相信息的java进程id

 

使用示例
查询jvm堆的概要信息

复制代码
blue@blue-pc:~/apache-tomcat-7.0.39/conf$ jps -ml
2491 
9142 org.apache.catalina.startup.Bootstrap start
9168 sun.tools.jps.Jps -ml
2967 

root@blue-pc:/home/blue/apache-tomcat-7.0.39/conf# jmap -heap 9142
Attaching to process ID 9142, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 20.10-b01

using thread-local object allocation.
Parallel GC with 4 thread(s)

Heap Configuration:
   MinHeapFreeRatio = 40
   MaxHeapFreeRatio = 70
   MaxHeapSize      = 1031798784 (984.0MB)
   NewSize          = 1048576 (1.0MB)
   MaxNewSize       = 4294901760 (4095.9375MB)
   OldSize          = 4194304 (4.0MB)
   NewRatio         = 2
   SurvivorRatio    = 8
   PermSize         = 16777216 (16.0MB)
   MaxPermSize      = 67108864 (64.0MB)

Heap Usage:
PS Young Generation
Eden Space:
   capacity = 16121856 (15.375MB)
   used     = 15074368 (14.37603759765625MB)
   free     = 1047488 (0.99896240234375MB)
   93.50268356199187% used
From Space:
   capacity = 2686976 (2.5625MB)
   used     = 2684584 (2.5602188110351562MB)
   free     = 2392 (0.00228118896484375MB)
   99.91097799161585% used
To Space:
   capacity = 2686976 (2.5625MB)
   used     = 0 (0.0MB)
   free     = 2686976 (2.5625MB)
   0.0% used
PS Old Generation
   capacity = 42991616 (41.0MB)
   used     = 5071824 (4.8368682861328125MB)
   free     = 37919792 (36.16313171386719MB)
   11.797239722275153% used
PS Perm Generation
   capacity = 16777216 (16.0MB)
   used     = 11304456 (10.780769348144531MB)
   free     = 5472760 (5.219230651855469MB)
   67.37980842590332% used
复制代码
 

dump jvm内存信息

复制代码
root@blue-pc:/home/blue/apache-tomcat-7.0.39/conf# jmap -F -dump:format=b,file=tomcat.bin 9142
Attaching to process ID 9142, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 20.10-b01
Dumping heap to tomcat.bin ...
Finding object size using Printezis bits and skipping over...
Heap dump file created
复制代码
 

jhat
用途：是用来分析java堆的命令，可以将堆中的对象以html的形式显示出来，包括对象的数量，大小等等，并支持对象查询语言

生成tomcat.bin dump文件后，使用jhat查看

root@blue-pc:/home/blue/apache-tomcat-7.0.39/conf# jhat tomcat.bin
.....
Started HTTP server on port 7000
Server is ready.
访问 http://localhost:7000，就可以查看详细的内存信息

有时你dump出来的堆很大，在启动时会报堆空间不足的错误，可以使用如下参数：

jhat -J-Xmx512m <heap dump file>

http://www.cnblogs.com/ggjucheng/archive/2013/04/16/3024986.html
http://blog.csdn.net/gtuu0123/article/details/6039474

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