JVM performance tuning and monitoring tools -- JPS, jstack, jmap, jhat, jstat, hprof

1. summary

In the last article , We introduced what scenarios would cause java Memory leaks . However , In many cases , Memory leak 、 Out of memory 、CPU It is easy to restart the server in case of high occupancy 、 Add memory and other processing methods to hide , Most of the java Programmers don't go into the root of the problem . this paper , We're going to learn java Performance monitoring provided 、 Tuning Tools , To locate 、 Solve these problems that are easy to be hidden .

2. jps

jps (Java Virtual Machine Process Status Tool) Is used for output jvm Tools for running status information .

2.1. Grammar format

• jps [options] [hostid] If you don't specify hostid The default is the current host .

2.2. Command line optional parameters

• -q — Do not output class name 、Jar Name and pass in main Method parameters
• -m — Output incoming main Method parameters
• -l — Output main Class or Jar The full name of
• -v — Output incoming JVM Parameters of

2.3. example

[email protected] ~ $ jps -ml46082 com.intellij.database.remote.RemoteJdbcServer com.mysql.jdbc.Driver17125 org.jetbrains.jps.cmdline.Launcher /Applications/IntelliJ IDEA.app/Contents/lib/javac2.jar:/Applications/IntelliJ IDEA.app/Contents/lib/oromatcher.jar:/Applications/IntelliJ IDEA.app/Contents/lib/jgoodies-forms.jar:/Applications/IntelliJ IDEA.app/Contents/lib/asm-all.jar:/Applications/IntelliJ IDEA.app/Contents/lib/commons-codec-1.9.jar:/Applications/IntelliJ IDEA.app/Contents/lib/protobuf-2.5.0.jar:/Applications/IntelliJ IDEA.app/Contents/lib/httpcore-4.4.5.jar:/Applications/IntelliJ IDEA.app/Contents/lib/jna-platform.jar:/Applications/IntelliJ IDEA.app/Contents/lib/netty-all-4.1.10.Final.jar:/Applications/IntelliJ IDEA.app/Contents/lib/jps-model.jar:/Applications/IntelliJ IDEA.app/Contents/lib/util.jar:/Applications/IntelliJ IDEA.app/Contents/lib/slf4j-api-1.7.10.jar:/Applications/IntelliJ IDEA.app/Contents/lib/aether-1.1.0-all.jar:/Applications/IntelliJ IDEA.app/Contents/lib/snappy-in-java-0.5.1.jar:/Applications/IntelliJ IDEA.app/Contents/lib/jna.jar:/Applications/IntelliJ IDEA.app/Contents/lib/openapi.ja49302 sun.tools.jps.Jps -ml17128 org.jetbrains.jps.cmdline.Launcher /Applications/IntelliJ IDEA.app/Contents/lib/javac2.jar:/Applications/IntelliJ IDEA.app/Contents/lib/oromatcher.jar:/Applications/IntelliJ IDEA.app/Contents/lib/jgoodies-forms.jar:/Applications/IntelliJ IDEA.app/Contents/lib/asm-all.jar:/Applications/IntelliJ IDEA.app/Contents/lib/commons-codec-1.9.jar:/Applications/IntelliJ IDEA.app/Contents/lib/protobuf-2.5.0.jar:/Applications/IntelliJ IDEA.app/Contents/lib/httpcore-4.4.5.jar:/Applications/IntelliJ IDEA.app/Contents/lib/jna-platform.jar:/Applications/IntelliJ IDEA.app/Contents/lib/netty-all-4.1.10.Final.jar:/Applications/IntelliJ IDEA.app/Contents/lib/jps-model.jar:/Applications/IntelliJ IDEA.app/Contents/lib/util.jar:/Applications/IntelliJ IDEA.app/Contents/lib/slf4j-api-1.7.10.jar:/Applications/IntelliJ IDEA.app/Contents/lib/aether-1.1.0-all.jar:/Applications/IntelliJ IDEA.app/Contents/lib/snappy-in-java-0.5.1.jar:/Applications/IntelliJ IDEA.app/Contents/lib/jna.jar:/Applications/IntelliJ IDEA.app/Contents/lib/openapi.ja17146 org.jetbrains.idea.maven.server.RemoteMavenServer17102

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3. jstack

jstack It is mainly used to view a certain Java In process thread stack information . The syntax is as follows ：

3.1. Grammar format

• jstack [option] <pid> (to connect to process)
• jstack [option] <executable> <core> (to connect to a core file)
• jstack [option] [[email protected]]<remote server IP or hostname> (to connect to a remote debug server)

3.2. Command line arguments

jstack The command has the following optional parameters :

• -F — mandatory dump Threads , Usually used for the output of unresponsive thread information
• -m — mixed mode, Not only will it output Java Stack information , It will also output C/C++ Stack information （ such as Native Method ）
• -l — long listings, Will print out additional lock information , It can be used in the lock of life and death jstack -l pid To observe lock holding
• -h or -help — Print help

3.3. Use — find java Most consumed in process CPU Code for

jstack It's for printing java Thread stack information in the process , Through the stack information, we can locate the specific code , stay jvm The tuning process uses a lot . Now let's talk about how to find a java Most consumed in process CPU Of java Threads .

Find out the process ID — ps First we pass ps Command found running on jetty In container java process pid.

Find occupancy CPU The longest thread — top -Hp pid Next , We go through top Command to find the occupation in the process CPU The longest thread ID.

We found the thread ID — 31078.

Output thread stack information — jstack First, through printf "%x\n" 31078 Command calculation thread ID Of 16 The base value is 7966, Next , We just need to call jstack,grep 7966 You can find it CPU What code is consumed .

We see that this thread is in waiting on condition The state of , Indicates that he is waiting for an event to trigger . adopt cat Combination of orders sed command , We can finally get the next few lines of data in this line ：

"MnsCacheManager-Schedule-1-thread-1" #68 daemon prio=5 os_prio=0 tid=0x00007fd225e0f800 nid=0x7966 waiting on condition [0x00007fd108830000]
   java.lang.Thread.State: TIMED_WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x000000073b44d090> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
        at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)
        at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1093)
        at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)
        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)

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You can see , Threads in the TIMED_WAITING state , Indicates that the threads in this thread pool are sleeping , Waiting to wake up , And the timeout is set .

3.4. Location of deadlock problem

Deadlock is a very common and easily overlooked problem in code , Here's a jstack Output , It clearly shows the existence of deadlocks and the specific location of the code .

"t2" prio=5 tid=0x00007fd9d30ac000 nid=0x5903 waiting for monitor entry [0x000000011da46000]
  java.lang.Thread.State: BLOCKED (on object monitor)
  at DeadLock$2.run(DeadLock.java:38)
  - waiting to lock <0x00000007aaba7e58> (a java.lang.Object)
  - locked <0x00000007aaba7e68> (a java.lang.Object)

  Locked ownable synchronizers:
  - None"t1" prio=5 tid=0x00007fd9d30ab800 nid=0x5703 waiting for monitor entry [0x000000011d943000]
  java.lang.Thread.State: BLOCKED (on object monitor)
  at DeadLock$1.run(DeadLock.java:23)
  - waiting to lock <0x00000007aaba7e68> (a java.lang.Object)
  - locked <0x00000007aaba7e58> (a java.lang.Object)

  Locked ownable synchronizers:
  - None

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You can see , Threads t1 Waiting for the lock , Threads t2 Waiting for the lock, too , Both sides also occupy the other side's waiting lock , Thus, the existence of deadlock can be easily determined .

4. jmap

jmap (JVM Memory Map) The command is used to generate heap dump file . You can also query through optional parameters finalize Perform the queue 、Java Heap and permanent generation details , Such as the current usage rate 、 What kind of collector is currently used .

4.1. jmap Grammar format

• jmap [option] <pid>
• jmap [option] <executable <core> (to connect to a core file)
• jmap [option] [[email protected]]<remote server IP or hostname> (to connect to remote debug server)

4.2. Optional parameters

• By default — Print heap memory dump The contents of the document
• -heap — Show java Heap details , Including the GC Algorithm 、 Heap configuration parameters and heap memory usage in each generation
• -histo — Displays the details of the objects in the heap
• -histo:live — Display the details of the surviving objects in the heap
• -permstat — Show java Persistent generation classloader statistics in heap memory
• -finalizerinfo — Displayed in the F-Queue Waiting in the queue for execution finalizer Object of method
• -dump — Generate a roll out snapshot of heap memory
• -F — -dump When there is no response , Force snapshot generation

4.3. explain

It should be noted that , If you start with java Version and jmap The version of is different , You're going to report a mistake . This usually happens when multiple versions of the are installed on the machine jdk package , You need to look for the version you need to use .

[[email protected] ~]$ jmap -heap 22845Attaching to process ID 22845, please wait...
Exception in thread "main" java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at sun.tools.jmap.JMap.runTool(JMap.java:197)
    at sun.tools.jmap.JMap.main(JMap.java:128)
Caused by: sun.jvm.hotspot.runtime.VMVersionMismatchException: Supported versions are 24.76-b04. Target VM is 25.45-b02
    at sun.jvm.hotspot.runtime.VM.checkVMVersion(VM.java:234)
    at sun.jvm.hotspot.runtime.VM.<init>(VM.java:297)
    at sun.jvm.hotspot.runtime.VM.initialize(VM.java:368)
    at sun.jvm.hotspot.bugspot.BugSpotAgent.setupVM(BugSpotAgent.java:598)
    at sun.jvm.hotspot.bugspot.BugSpotAgent.go(BugSpotAgent.java:493)
    at sun.jvm.hotspot.bugspot.BugSpotAgent.attach(BugSpotAgent.java:331)
    at sun.jvm.hotspot.tools.Tool.start(Tool.java:163)
    at sun.jvm.hotspot.tools.HeapSummary.main(HeapSummary.java:40)
    ... 6 more

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5. jhat

If you think jmap The printed results are not intuitive , Don't worry ,java It also provides an easy-to-use browser interface analysis tool jhat. JVM Heap Analysis Tool The order is with jmap Use it with , Used for analysis jmap Generated dump,jhat Built in a micro HTTP/HTML The server , Generate dump After analyzing the results of , You can view... In a browser .

5.1. Usage mode

First, through jmap Output heap memory dump file

then , adopt jhat Command specifies the port , You can view it in the browser

5.2. Print field meaning

• S0C、S1C、S0U、S1U — Survivor 0/1 Area capacity （Capacity） And usage （Used）
• EC、EU — Eden Area capacity and usage
• OC、OU — Capacity and usage of older generations
• PC、PU — Permanent generation capacity and usage
• YGC、YGT — The younger generation GC Times and GC Time consuming
• FGC、FGCT — Full GC Times and Full GC Time consuming
• GCT — GC Total time

6. Reference material

Yu Huo — http://www.cnblogs.com/myna/ JVM Performance tuning monitoring tool jps、jstack、jmap、jhat、jstat、hprof The use of, — https://blog.csdn.net/dragonassassin/article/details/51010947.