前言
大家都知道有很多開源的監控工具，本次只使用了jmap，了解簡單使用，謝謝，下面話不多說了，來一起看看詳細的介紹吧
使用方法如下：
開始了，922是我的tomcat進程
幫助命令查看，有哪些命令可以使用。
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[root@bogon /]# jmap -helpusage: jmap [option] <pid> (to connect to running process) jmap [option] <executable <core> (to connect to a core file) jmap [option] [server_id@]<remote server ip or hostname> (to connect to remote debug server)where <option> is one of: <none> to print same info as solaris pmap -heap to print java heap summary -histo[:live] to print histogram of java object heap; if the "live" suboption is specified, only count live objects -clstats to print class loader statistics -finalizerinfo to print information on objects awaiting finalization -dump:<dump-options> to dump java heap in hprof binary format dump-options: live dump only live objects; if not specified, all objects in the heap are dumped. format=b binary format file=<file> dump heap to <file> example: jmap -dump:live,format=b,file=heap.bin <pid> -f force. use with -dump:<dump-options> <pid> or -histo to force a heap dump or histogram when <pid> does not respond. the "live" suboption is not supported in this mode. -h | -help to print this help message -j<flag> to pass <flag> directly to the runtime system |
使用1：jmap pid 查看基本信息
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[root@bogon /]# jmap 922attaching to process id 922, please wait...debugger attached successfully.server compiler detected.0x0000000000400000 7k /usr/local/software/java/bin/java0x0000003ddde00000 153k /lib64/ld-2.12.so0x0000003dde200000 22k /lib64/libdl-2.12.so0x0000003dde600000 1881k /lib64/libc-2.12.so0x0000003ddea00000 142k /lib64/libpthread-2.12.so0x0000003ddee00000 45k /lib64/librt-2.12.so0x0000003ddf200000 585k /lib64/libm-2.12.so0x0000003de0e00000 111k /lib64/libresolv-2.12.so0x0000003de9e00000 91k /lib64/libgcc_s-4.4.7-20120601.so.10x00007f90de586000 26k /lib64/libnss_dns-2.12.so0x00007f913c39d000 250k /usr/local/software/java/jre/lib/amd64/libsunec.so0x00007f913cbf2000 90k /usr/local/software/java/jre/lib/amd64/libnio.so0x00007f913d103000 113k /usr/local/software/java/jre/lib/amd64/libnet.so0x00007f913d31a000 49k /usr/local/software/java/jre/lib/amd64/libmanagement.so0x00007f919a43b000 121k /usr/local/software/java/jre/lib/amd64/libzip.so0x00007f919a656000 64k /lib64/libnss_files-2.12.so0x00007f919a874000 220k /usr/local/software/java/jre/lib/amd64/libjava.so0x00007f919aaa0000 64k /usr/local/software/java/jre/lib/amd64/libverify.so0x00007f919acef000 16584k /usr/local/software/java/jre/lib/amd64/server/libjvm.so0x00007f919bce2000 100k /usr/local/software/java/lib/amd64/jli/libjli.so |
使用2 ：查看堆信息，jmap -heap pid
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[root@bogon /]# jmap -heap 922attaching to process id 922, please wait...debugger attached successfully.server compiler detected.jvm version is 25.111-b14using parallel threads in the new generation. using thread-local object allocation.concurrent mark-sweep gcheap configuration: minheapfreeratio = 40 maxheapfreeratio = 70 maxheapsize = 4294967296 (4096.0mb) 最大堆大小 newsize = 3221225472 (3072.0mb) 新生代大小 maxnewsize = 3221225472 (3072.0mb) 最大分配新生代內存 oldsize = 1073741824 (1024.0mb) 老年代大小 newratio = 2 survivorratio = 8 新生代與老年代的比例 metaspacesize = 21807104 (20.796875mb) compressedclassspacesize = 1073741824 (1024.0mb) maxmetaspacesize = 17592186044415 mb g1heapregionsize = 0 (0.0mb)heap usage: 堆的使用情況new generation (eden + 1 survivor space): 新生代 capacity = 2899116032 (2764.8125mb) used = 384206560 (366.4079284667969mb) free = 2514909472 (2398.404571533203mb) 13.25254166301682% usededen space: 新生代 eden區空間 capacity = 2577006592 (2457.625mb) used = 378654344 (361.11292266845703mb) free = 2198352248 (2096.512077331543mb) 14.693572968555294% usedfrom space: 2個survivor區域 其中一個就是這個from區 capacity = 322109440 (307.1875mb) used = 5552216 (5.295005798339844mb) free = 316557224 (301.89249420166016mb) 1.723704837709817% usedto space:2個survivor區域 其中一個就是這個to區 capacity = 322109440 (307.1875mb) used = 0 (0.0mb) free = 322109440 (307.1875mb) 0.0% usedconcurrent mark-sweep generation: 老年代 eden區空間 capacity = 1073741824 (1024.0mb) used = 846734040 (807.5085067749023mb) free = 227007784 (216.49149322509766mb) 78.85825261473656% used |
使用3：jmap -histo pid 查看一些class的使用情況，
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jmap -histo 922由于里面比較多內容，所以放棄了，可以自己使用一下，如果電腦展示不了一屏呢，可以這樣。jmap -histo 922 >dump.txt 導出文件，可以自己看了下面是我自己導出的文件信息 num #instances(實例數量) #bytes（字節） class name ---------------------------------------------- 1: 174069 1579369600 [c 2: 4403 122732640 [i 3: 9571 16889072 [b 4: 157680 3784320 java.lang.string 5: 38279 3674784 java.util.jar.jarfile$jarfileentry 6: 70982 2271424 java.util.hashmap$node 7: 13235 1164680 java.lang.reflect.method 8: 6001 1028952 [ljava.util.hashmap$node;又或者可以過濾信息，命令：jmap -histo 922 |grep dubbo 過濾一下，就過濾你想要的信息 |
使用4：jmap -histo:live pid >dump.txt
這個和使用3差不多，都是在統計，只不過這個是在統計正在使用的對象，然后dump對象信息。
這種命令都是結合其它的命令一起使用的，以后會有文章結合一起分析，同學有什么好的工具也分享出來，一起學習，本篇只介紹jmap
總結
以上就是這篇文章的全部內容了，希望本文的內容對大家的學習或者工作具有一定的參考學習價值，如果有疑問大家可以留言交流，謝謝大家對服務器之家的支持。
原文鏈接：http://blog.51cto.com/shangdc/2151219
