Jinfo

查看正在运行的Java应用程序的扩展参数。

>jinfo --help
Usage:jinfo [option] <pid>(to connect to running process)jinfo [option] <executable <core>(to connect to a core file)jinfo [option] [server_id@]<remote server IP or hostname>(to connect to remote debug server)where <option> is one of:-flag <name>         to print the value of the named VM flag-flag [+|-]<name>    to enable or disable the named VM flag-flag <name>=<value> to set the named VM flag to the given value-flags               to print VM flags-sysprops            to print Java system properties<no option>          to print both of the above-h | -help           to print this help message

主要掌握两个命令，一个是查看JVM参数的命令，一个是查看JAVA系统参数的命令。

查看JVM参数

查看JVM参数的命令>jinfo -flags 进程IDAttaching to process ID 4746, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.211-b12
Non-default VM flags: -XX:CICompilerCount=3 -XX:CompressedClassSpaceSize=260046848 -XX:ConcGCThreads=1 -XX:+DisableExplicitGC -XX:ErrorFile=null -XX:G1HeapRegionSize=1048576 -XX:InitialHeapSize=536870912 -XX:InitialTenuringThreshold=7 -XX:InitiatingHeapOccupancyPercent=45 -XX:MarkStackSize=4194304 -XX:MaxGCPauseMillis=200 -XX:MaxHeapSize=4294967296 -XX:MaxMetaspaceSize=268435456 -XX:MaxNewSize=2576351232 -XX:MinHeapDeltaBytes=1048576 -XX:+PrintGC -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:ReservedCodeCacheSize=134217728 -XX:+TieredCompilation -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseG1GC -XX:+UseStringDeduplication

查看JAVA系统参数

查看JAVA系统参数的命令>jinfo -sysprops 进程IDAttaching to process ID 4746, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.211-b12
java.runtime.name = Java(TM) SE Runtime Environment
java.vm.version = 25.211-b12
java.io.tmpdir = /tmp

Jmap

可以用来查看内存信息。

>jmap -help
Usage: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 formatdump-options:live         dump only live objects; if not specified,all objects in the heap are dumped.format=b     binary formatfile=<file>  dump heap to <file>Example: jmap -dump:live,format=b,file=heap.bin <pid>-F                   force. Use with -dump:<dump-options> <pid> or -histoto force a heap dump or histogram when <pid> does notrespond. The "live" suboption is not supportedin this mode.-h | -help           to print this help message-J<flag>             to pass <flag> directly to the runtime system

查看JAVA堆信息

打印Java堆摘要>jmap -heap 进程IDAttaching to process ID 4746, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.211-b12using thread-local object allocation.
Garbage-First (G1) GC with 4 thread(s)Heap Configuration:MinHeapFreeRatio         = 40MaxHeapFreeRatio         = 70MaxHeapSize              = 4294967296 (4096.0MB)NewSize                  = 1363144 (1.2999954223632812MB)MaxNewSize               = 2576351232 (2457.0MB)OldSize                  = 5452592 (5.1999969482421875MB)NewRatio                 = 2SurvivorRatio            = 8MetaspaceSize            = 21807104 (20.796875MB)CompressedClassSpaceSize = 260046848 (248.0MB)MaxMetaspaceSize         = 268435456 (256.0MB)G1HeapRegionSize         = 1048576 (1.0MB)Heap Usage:
G1 Heap:regions  = 4096capacity = 4294967296 (4096.0MB)used     = 377291272 (359.81299591064453MB)free     = 3917676024 (3736.1870040893555MB)8.78449697047472% used
G1 Young Generation:
Eden Space:regions  = 269capacity = 331350016 (316.0MB)used     = 282066944 (269.0MB)free     = 49283072 (47.0MB)85.12658227848101% used
Survivor Space:regions  = 7capacity = 7340032 (7.0MB)used     = 7340032 (7.0MB)free     = 0 (0.0MB)100.0% used
G1 Old Generation:regions  = 85capacity = 198180864 (189.0MB)used     = 87884296 (83.81299591064453MB)free     = 110296568 (105.18700408935547MB)44.345500481822505% used

查看JAVA对象堆信息

以一般格式文件转储Java对象堆[存活对象]的信息>jmap -histo[:live] 进程ID > map.txt

转储JAVA对象堆信息

以hprof二进制格式转储Java堆信息>jmap -dump:format=b,file=charging.hprof 进程ID

Jstack

可以用来查看线程信息，典型的可以查找死锁。

jstack -help
Usage:jstack [-l] <pid>(to connect to running process)jstack -F [-m] [-l] <pid>(to connect to a hung process)jstack [-m] [-l] <executable> <core>(to connect to a core file)jstack [-m] [-l] [server_id@]<remote server IP or hostname>(to connect to a remote debug server)Options:-F  to force a thread dump. Use when jstack <pid> does not respond (process is hung)-m  to print both java and native frames (mixed mode)-l  long listing. Prints additional information about locks-h or -help to print this help message

查看死锁信息

>jstack 进程IDFound one Java-level deadlock:
=============================
"Thread-1":waiting to lock monitor 0x00007fec2a03f418 (object 0x0000000797608600, a java.lang.Object),which is held by "Thread-0"
"Thread-0":waiting to lock monitor 0x00007fec2a041ca8 (object 0x0000000797608610, a java.lang.Object),which is held by "Thread-1"Java stack information for the threads listed above:
===================================================
"Thread-1":at com.ambition.study.DeadLockTest.lambda$main$1(DeadLockTest.java:38)- waiting to lock <0x0000000797608600> (a java.lang.Object)- locked <0x0000000797608610> (a java.lang.Object)at com.ambition.study.DeadLockTest$$Lambda$2/1922154895.run(Unknown Source)at java.lang.Thread.run(Thread.java:748)
"Thread-0":at com.ambition.study.DeadLockTest.lambda$main$0(DeadLockTest.java:23)- waiting to lock <0x0000000797608610> (a java.lang.Object)- locked <0x0000000797608600> (a java.lang.Object)at com.ambition.study.DeadLockTest$$Lambda$1/793589513.run(Unknown Source)at java.lang.Thread.run(Thread.java:748)Found 1 deadlock.

Jstat

可以查看堆内存各部分的使用量，以及加载类的数量。

jstat -help
Usage: jstat -help|-optionsjstat -<option> [-t] [-h<lines>] <vmid> [<interval> [<count>]]Definitions:<option>      An option reported by the -options option<vmid>        Virtual Machine Identifier. A vmid takes the following form:<lvmid>[@<hostname>[:<port>]]Where <lvmid> is the local vm identifier for the targetJava virtual machine, typically a process id; <hostname> isthe name of the host running the target Java virtual machine;and <port> is the port number for the rmiregistry on thetarget host. See the jvmstat documentation for a more completedescription of the Virtual Machine Identifier.<lines>       Number of samples between header lines.<interval>    Sampling interval. The following forms are allowed:<n>["ms"|"s"]Where <n> is an integer and the suffix specifies the units asmilliseconds("ms") or seconds("s"). The default units are "ms".<count>       Number of samples to take before terminating.-J<flag>      Pass <flag> directly to the runtime system.

jstat [-命令选项] [vmid] [间隔时间(毫秒)] [查询次数]

垃圾回收统计

垃圾回收统计>jstat -gc 进程IDS0C    S1C    S0U    S1U      EC       EU        OC         OU       MC        MU      CCSC   CCSU     YGC     YGCT    FGC    FGCT     GCT
0.0   6144.0  0.0   6144.0 324608.0 45056.0   193536.0   76996.9  134328.0 128112.0 16568.0 15547.2   1043   15.308   2      0.850   16.158S0C:第一个幸存区的大小
S1C:第二个幸存区的大小
S0U:第一个幸存区的使用大小
S1U:第二个幸存区的使用大小
EC:伊甸园区的大小
EU:伊甸园区的使用大小
OC:老年代大小
OU:老年代使用大小
MC:方法区大小(元空间)
MU:方法区使用大小
CCSC:压缩类空间大小
CCSU:压缩类空间使用大小
YGC:年轻代垃圾回收次数
YGCT:年轻代垃圾回收消耗时间，单位s
FGC:老年代垃圾回收次数
FGCT:老年代垃圾回收消耗时间，单位s
GCT:垃圾回收消耗总时间，单位s

堆内存统计

堆内存统计>jstat -gccapacity 进程IDNGCMN    NGCMX     NGC     S0C   S1C       EC      OGCMN      OGCMX       OGC         OC       MCMN     MCMX      MC     CCSMN    CCSMX     CCSC    YGC    FGC
0.0    4194304.0  330752.0  0.0  6144.0  324608.0   0.0     4194304.0   193536.0   193536.0    0.0    1167360.0 134328.0  0.0   1048576.0  16568.0  1045   2NGCMN:新生代最小容量
NGCMX:新生代最大容量
NGC:当前新生代容量
S0C:第一个幸存区大小
S1C:第二个幸存区的大小
EC:伊甸园区的大小
OGCMN:老年代最小容量
OGCMX:老年代最大容量
OGC:当前老年代大小
OC:当前老年代大小
MCMN:最小元数据容量
MCMX:最大元数据容量
MC:当前元数据空间大小
CCSMN:最小压缩类空间大小
CCSMX:最大压缩类空间大小
CCSC:当前压缩类空间大小
YGC:年轻代gc次数
FGC:老年代GC次数

新生代垃圾回收统计

新生代垃圾回收统计>jstat -gcnew 进程IDS0C    S1C    S0U    S1U    TT   MTT   DSS      EC       EU      YGC     YGCT
0.0   7168.0  0.0   7168.0  15   15   19968.0 323584.0 217088.0  1050   15.405S0C:第一个幸存区的大小
S1C:第二个幸存区的大小
S0U:第一个幸存区的使用大小
S1U:第二个幸存区的使用大小
TT:对象在新生代存活的次数
MTT:对象在新生代存活的最大次数
DSS:期望的幸存区大小
EC:伊甸园区的大小
EU:伊甸园区的使用大小
YGC:年轻代垃圾回收次数
YGCT:年轻代垃圾回收消耗时间

新生代内存统计

新生代内存统计>jstat -gcnewcapacity 进程IDNGCMN      NGCMX       NGC      S0CMX     S0C     S1CMX     S1C       ECMX        EC      YGC   FGC
0.0      4194304.0   330752.0    0.0      0.0   4194304.0   8192.0  4194304.0   322560.0  1052   2NGCMN:新生代最小容量
NGCMX:新生代最大容量
NGC:当前新生代容量
S0CMX:最大幸存1区大小
S0C:当前幸存1区大小
S1CMX:最大幸存2区大小
S1C:当前幸存2区大小
ECMX:最大伊甸园区大小
EC:当前伊甸园区大小 
YGC:年轻代垃圾回收次数
FGC:老年代回收次数

老年代垃圾回收统计

老年代垃圾回收统计>jstat -gcold 进程IDMC          MU      CCSC     CCSU       OC          OU       YGC    FGC    FGCT     GCT
134328.0 128112.0  16568.0  15547.2    193536.0   77731.4    1053     2    0.850   16.297MC:方法区大小 
MU:方法区使用大小 
CCSC:压缩类空间大小 
CCSU:压缩类空间使用大小 
OC:老年代大小 
OU:老年代使用大小 
YGC:年轻代垃圾回收次数 
FGC:老年代垃圾回收次数 
FGCT:老年代垃圾回收消耗时间 
GCT:垃圾回收消耗总时间

老年代内存统计

老年代内存统计>jstat -gcoldcapacity 进程IDOGCMN       OGCMX        OGC         OC       YGC   FGC    FGCT     GCT
0.0       4194304.0    193536.0    193536.0  1053     2    0.850   16.297OGCMN:老年代最小容量 
OGCMX:老年代最大容量 
OGC:当前老年代大小 
OC:老年代大小 
YGC:年轻代垃圾回收次数 
FGC:老年代垃圾回收次数 
FGCT:老年代垃圾回收消耗时间 
GCT:垃圾回收消耗总时间

元空间数据统计

元空间数据统计>jstat -gcmetacapacity 进程IDMCMN       MCMX        MC       CCSMN      CCSMX       CCSC     YGC   FGC    FGCT     GCT
0.0     1167360.0   134328.0     0.0     1048576.0    16568.0  1054    2    0.850   16.308MCMN:最小元数据容量 
MCMX:最大元数据容量 
MC:当前元数据空间大小 
CCSMN:最小压缩类空间大小 
CCSMX:最大压缩类空间大小 
CCSC:当前压缩类空间大小 
YGC:年轻代垃圾回收次数 
FGC:老年代垃圾回收次数 
FGCT:老年代垃圾回收消耗时间 
GCT:垃圾回收消耗总时间