[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

[root@bogon /]# jmap 922Attaching to process ID 922, please wait...Debugger attached successfully.Server compiler detected.JVM version is 25.111-b140x0000000000400000 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

[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

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