1. jps，查看jvm实例
[root@test_back-1~]# jps -help
usage: jps [-help]
jps [-q] [-mlvV] [<hostid>]
Definitions:
<hostid>: <hostname>[:<port>]
[root@test_back-1~]# jps -q
30262
28666
20794
30109
[root@test_back-1~]# jps -m
20806 Jps -m
30262 Bootstrap start
28666 jar
30109 Bootstrap start
2. jstat，jvm统计信息，包含内存信息及GC信息
[root@test_back-1~]# jstat -help
Usage: jstat -help|-options
jstat -<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 target
Java virtual machine, typically a process id; <hostname> is
the name of the host running the target Java virtual machine;
and <port> is the port number for the rmiregistry on the
target host. See the jvmstat documentation for a more complete
description 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 as
milliseconds("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.
[root@test_back-1~]# jstat -options
-class
-compiler
-gc
-gccapacity
-gccause
-gcmetacapacity
-gcnew
-gcnewcapacity
-gcold
-gcoldcapacity
-gcutil
-printcompilation
[root@test_back-1~]#
[root@test_back-1~]# jstat -gc -t -h10 30109 1500ms 3
Timestamp S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT
89872.2 17024.0 17024.0 560.1 0.0 136320.0 112080.7 878208.0 48104.2 82732.0 79226.9 9772.0 9139.9 1258 10.912 6 0.271 11.183
89873.7 17024.0 17024.0 560.1 0.0 136320.0 115375.3 878208.0 48104.2 82732.0 79226.9 9772.0 9139.9 1258 10.912 6 0.271 11.183
89875.2 17024.0 17024.0 560.1 0.0 136320.0 117665.7 878208.0 48104.2 82732.0 79226.9 9772.0 9139.9 1258 10.912 6 0.271 11.183
3. jmap，查看JVM内存相关信息
[root@test_back-1~]# 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 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@test_back-1~]# jmap -heap 30109
Attaching to process ID 30109, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.74-b02
using parallel threads in the new generation.
using thread-local object allocation.
Concurrent Mark-Sweep GC
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 1073741824 (1024.0MB)
NewSize = 174456832 (166.375MB)
MaxNewSize = 174456832 (166.375MB)
OldSize = 899284992 (857.625MB)
NewRatio = 2
SurvivorRatio = 8
MetaspaceSize = 21807104 (20.796875MB)
CompressedClassSpaceSize = 1073741824 (1024.0MB)
MaxMetaspaceSize = 17592186044415 MB
G1HeapRegionSize = 0 (0.0MB)
Heap Usage:
New Generation (Eden + 1 Survivor Space):
capacity = 157024256 (149.75MB)
used = 46988880 (44.81208801269531MB)
free = 110035376 (104.93791198730469MB)
29.924599674587856% used
Eden Space:
capacity = 139591680 (133.125MB)
used = 46461032 (44.308692932128906MB)
free = 93130648 (88.8163070678711MB)
33.283525207232984% used
From Space:
capacity = 17432576 (16.625MB)
used = 527848 (0.5033950805664062MB)
free = 16904728 (16.121604919433594MB)
3.0279403342340228% used
To Space:
capacity = 17432576 (16.625MB)
used = 0 (0.0MB)
free = 17432576 (16.625MB)
0.0% used
concurrent mark-sweep generation:
capacity = 899284992 (857.625MB)
used = 49281872 (46.99885559082031MB)
free = 850003120 (810.6261444091797MB)
5.480117252974239% used
29566 interned Strings occupying 3583576 bytes.
4. jstack，查看java栈及本地方法栈信息
[root@test_back-1~]# 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
[root@test_back-1~]# jstack -l 30109
"Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007f1e80120000 nid=0x75a5 in Object.wait() [0x00007f1e84a61000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:502)
at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
- locked <0x00000000ca967f48> (a java.lang.ref.Reference$Lock)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
Locked ownable synchronizers:
- None
"main" #1 prio=5 os_prio=0 tid=0x00007f1e8000a000 nid=0x759f runnable [0x00007f1e87d70000]
java.lang.Thread.State: RUNNABLE
at java.net.PlainSocketImpl.socketAccept(Native Method)
at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409)
at java.net.ServerSocket.implAccept(ServerSocket.java:545)
at java.net.ServerSocket.accept(ServerSocket.java:513)
at org.apache.catalina.core.StandardServer.await(StandardServer.java:466)
at org.apache.catalina.startup.Catalina.await(Catalina.java:743)
at org.apache.catalina.startup.Catalina.start(Catalina.java:689)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:355)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:495)
Locked ownable synchronizers:
- None
"VM Thread" os_prio=0 tid=0x00007f1e80118800 nid=0x75a4 runnable
"Gang worker#0 (Parallel GC Threads)" os_prio=0 tid=0x00007f1e8001b000 nid=0x75a0 runnable
"Gang worker#1 (Parallel GC Threads)" os_prio=0 tid=0x00007f1e8001c800 nid=0x75a1 runnable
"Concurrent Mark-Sweep GC Thread" os_prio=0 tid=0x00007f1e8004a000 nid=0x75a2 runnable
"VM Periodic Task Thread" os_prio=0 tid=0x00007f1e80756000 nid=0x75b6 waiting on condition
JNI global references: 689
5. jinfo，查看jvm配置信息
[root@test_back-1~]# 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
[root@test_back-1~]# jinfo 30109
Attaching to process ID 30109, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.74-b02
Java System Properties:
java.vendor = Oracle Corporation
rocketmq.client.logFileName = ons.log
sun.java.launcher = SUN_STANDARD
catalina.base = /wdzj/java/tomcat_8080
...
java.vm.name = Java HotSpot(TM) 64-Bit Server VM
file.encoding = UTF-8
java.specification.version = 1.8
VM Flags:
Non-default VM flags: -XX:CICompilerCount=2 -XX:InitialHeapSize=1073741824 -XX:MaxHeapSize=1073741824 -XX:MaxNewSize=174456832 -XX:MaxTenuringThreshold=6 -XX:MinHeapDeltaBytes=196608 -XX:NewSize=174456832 -XX:OldPLABSize=16 -XX:OldSize=899284992 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -
示例：查看指定进程栈信息
[root@test_back-1 ~]# top -Hp 30109 #查看这个JVM进程里面的进程运行情况
top - 15:01:01 up 123 days, 8:43, 3 users, load average: 0.20, 0.13, 0.05
Tasks: 246 total, 0 running, 246 sleeping, 0 stopped, 0 zombie
Cpu(s): 1.5%us, 0.7%sy, 0.0%ni, 97.0%id, 0.8%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 3924700k total, 3654884k used, 269816k free, 160024k buffers
Swap: 3989496k total, 120700k used, 3868796k free, 1181444k cached
Unknown command - try 'h' for help
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
30126 root 20 0 3980m 762m 15m S 0.7 19.9 0:59.70 java
...
[root@test_back-1 ~]# printf "%x \n" 30126 #转换进程id为16进制
75ae
[root@test_back-1 ~]# jstack 30109|grep 75ae --color -C 5 #查看进程里面的栈信息
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
"DataCarrier.DEFAULT.Consumser.0.Thread" #10 daemon prio=5 os_prio=0 tid=0x00007f1e8070f000 nid=0x75ae sleeping[0x00007f1e84295000]
java.lang.Thread.State: TIMED_WAITING (sleeping)
at java.lang.Thread.sleep(Native Method)
at org.apache.skywalking.apm.commons.datacarrier.consumer.ConsumerThread.run(ConsumerThread.java:72)
"Thread-3" #9 daemon prio=5 os_prio=0 tid=0x00007f1e8026e000 nid=0x75aa waiting on condition [0x00007f1e84413000]
每一个使用之前都下查看帮助信息（-help）
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