jvm的调优过程分析与理解

╰半夏微凉° 2022-12-28 14:15 157阅读 0赞

#### 背景 ####

1.  在什么样的情况下，需要调优？
2.  调优的基础指令？
3.  调优实战过程的注意事项？

#### 过程 ####

*  **需要调优**

1.  **预调优**。在具体的业务场景下。比如客户预算只有那么点钱，买个云服务器部署项目。
2.  **慢，卡顿**。在具体的业务场景下。比如项目已经在生产环境跑起来了，出现了，**慢或者卡顿现象**。
3.  **OOM**。在具体的业务场景下。比如项目已经在生产环境跑起来了，出现了，**OOM**情况。

*  **调优的基础指令**

1.  java -X （查询非标准选项）

-Xmixed           混合模式执行 (默认)
        -Xint             仅解释模式执行
        -Xbootclasspath:<用 ; 分隔的目录和 zip/jar 文件>
                          设置搜索路径以引导类和资源
        -Xbootclasspath/a:<用 ; 分隔的目录和 zip/jar 文件>
                          附加在引导类路径末尾
        -Xbootclasspath/p:<用 ; 分隔的目录和 zip/jar 文件>
                          置于引导类路径之前
        -Xdiag            显示附加诊断消息
        -Xnoclassgc       禁用类垃圾收集
        -Xincgc           启用增量垃圾收集
        -Xloggc:<file>    将 GC 状态记录在文件中 (带时间戳)
        -Xbatch           禁用后台编译
        -Xms<size>        设置初始 Java 堆大小
        -Xmx<size>        设置最大 Java 堆大小
        -Xss<size>        设置 Java 线程堆栈大小
        -Xprof            输出 cpu 配置文件数据
        -Xfuture          启用最严格的检查, 预期将来的默认值
        -Xrs              减少 Java/VM 对操作系统信号的使用 (请参阅文档)
        -Xcheck:jni       对 JNI 函数执行其他检查
        -Xshare:off       不尝试使用共享类数据
        -Xshare:auto      在可能的情况下使用共享类数据 (默认)
        -Xshare:on        要求使用共享类数据, 否则将失败。
        -XshowSettings    显示所有设置并继续
        -XshowSettings:all
                          显示所有设置并继续
        -XshowSettings:vm 显示所有与 vm 相关的设置并继续
        -XshowSettings:properties
                          显示所有属性设置并继续
        -XshowSettings:locale
                          显示所有与区域设置相关的设置并继续
    
    -X 选项是非标准选项, 如有更改, 恕不另行通知。

1.  java -XX:+PrintCommandLineFlags -version （查询当前虚拟机使用了哪个垃圾收集器）

-XX:InitialHeapSize=328369216 
    -XX:MaxHeapSize=5253907456 
    -XX:+PrintCommandLineFlags 
    -XX:+UseCompressedClassPointers
    -XX:+UseCompressedOops 
    -XX:-UseLargePagesIndividualAllocation -XX:+UseParallelGC
    java version "1.8.0_181"
    Java(TM) SE Runtime Environment (build 1.8.0_181-b13)
    Java HotSpot(TM) 64-Bit Server VM (build 25.181-b13, mixed mode)

1.  jps （查询java 虚拟机的进程有哪些）

10592 Launcher
    5456 AttachfileApplication
    13416 BrokerStartup
    7608 Launcher
    10620 NamesrvStartup
    13596 Jps

1.  jinfo (查询java进行有哪些基础信息) jinfo 10620

Attaching to process ID 10620, please wait...
    Debugger attached successfully.
    Server compiler detected.
    JVM version is 25.181-b13
    Java System Properties:
    
    java.runtime.name = Java(TM) SE Runtime Environment
    java.vm.version = 25.181-b13
    sun.boot.library.path = C:\Program Files\Java\jdk1.8.0_181\jre\bin
    rocketmq.remoting.version = 355
    java.vendor.url = http://java.oracle.com/
    java.vm.vendor = Oracle Corporation
    path.separator = ;
    file.encoding.pkg = sun.io
    java.vm.name = Java HotSpot(TM) 64-Bit Server VM
    sun.os.patch.level =
    sun.java.launcher = SUN_STANDARD
    user.script =
    user.country = CN
    user.dir = E:\resource-code\rocketmq
    java.vm.specification.name = Java Virtual Machine Specification
    java.runtime.version = 1.8.0_181-b13
    java.awt.graphicsenv = sun.awt.Win32GraphicsEnvironment
    os.arch = amd64
    java.endorsed.dirs = C:\Program Files\Java\jdk1.8.0_181\jre\lib\endorsed
    line.separator =
    
    java.io.tmpdir = C:\Users\Sanding\AppData\Local\Temp\
    java.vm.specification.vendor = Oracle Corporation
    user.variant =
    os.name = Windows 10
    sun.jnu.encoding = GBK
    java.library.path = C:\Program Files\Java\jdk1.8.0_181\bin;C:\Windows\Sun\Java\bin;C:\Windows\system32;C:\Windows;C:\Program Files (x86)\Common Files\Oracle\Java\javapath;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Windows\System32\OpenSSH\;G:\apache-maven\apache-maven-3.5.3\bin;D:\Git\cmd;C:\Users\Sanding\AppData\Local\Microsoft\WindowsApps;;.
    sun.nio.ch.bugLevel =
    java.specification.name = Java Platform API Specification
    java.class.version = 52.0
    sun.management.compiler = HotSpot 64-Bit Tiered Compilers
    os.version = 10.0
    user.home = C:\Users\Sanding
    user.timezone = Asia/Shanghai
    java.awt.printerjob = sun.awt.windows.WPrinterJob
    file.encoding = UTF-8
    java.specification.version = 1.8
    user.name = Sanding
    java.class.path = C:\Program Files\Java\jdk1.8.0_181\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\rt.jar;E:\resource-code\rocketmq\namesrv\target\classes;E:\resource-code\rocketmq\client\target\classes;E:\resource-code\rocketmq\common\target\classes;F:\MavenRepository\commons-validator\commons-validator\1.6\commons-validator-1.6.jar;F:\MavenRepository\commons-beanutils\commons-beanutils\1.9.2\commons-beanutils-1.9.2.jar;F:\MavenRepository\commons-digester\commons-digester\1.8.1\commons-digester-1.8.1.jar;F:\MavenRepository\commons-logging\commons-logging\1.2\commons-logging-1.2.jar;F:\MavenRepository\commons-collections\commons-collections\3.2.2\commons-collections-3.2.2.jar;F:\MavenRepository\org\apache\commons\commons-lang3\3.4\commons-lang3-3.4.jar;E:\resource-code\rocketmq\tools\target\classes;E:\resource-code\rocketmq\acl\target\classes;E:\resource-code\rocketmq\logging\target\classes;F:\MavenRepository\commons-codec\commons-codec\1.9\commons-codec-1.9.jar;E:\resource-code\rocketmq\store\target\classes;F:\MavenRepository\io\openmessaging\storage\dledger\0.1\dledger-0.1.jar;F:\MavenRepository\com\beust\jcommander\1.72\jcommander-1.72.jar;F:\MavenRepository\net\java\dev\jna\jna\4.2.2\jna-4.2.2.jar;F:\MavenRepository\com\alibaba\fastjson\1.2.69\fastjson-1.2.69.jar;F:\MavenRepository\org\yaml\snakeyaml\1.19\snakeyaml-1.19.jar;E:\resource-code\rocketmq\srvutil\target\classes;E:\resource-code\rocketmq\remoting\target\classes;F:\MavenRepository\io\netty\netty-all\4.0.42.Final\netty-all-4.0.42.Final.jar;F:\MavenRepository\io\netty\netty-tcnative-boringssl-static\1.1.33.Fork26\netty-tcnative-boringssl-static-1.1.33.Fork26.jar;F:\MavenRepository\commons-cli\commons-cli\1.2\commons-cli-1.2.jar;F:\MavenRepository\ch\qos\logback\logback-classic\1.0.13\logback-classic-1.0.13.jar;F:\MavenRepository\ch\qos\logback\logback-core\1.0.13\logback-core-1.0.13.jar;F:\MavenRepository\org\slf4j\slf4j-api\1.7.7\slf4j-api-1.7.7.jar;D:\IntelliJ IDEA Community Edition 2020.1.2\lib\idea_rt.jar
    java.vm.specification.version = 1.8
    sun.arch.data.model = 64
    sun.java.command = org.apache.rocketmq.namesrv.NamesrvStartup
    java.home = C:\Program Files\Java\jdk1.8.0_181\jre
    user.language = zh
    java.specification.vendor = Oracle Corporation
    awt.toolkit = sun.awt.windows.WToolkit
    java.vm.info = mixed mode
    java.version = 1.8.0_181
    java.ext.dirs = C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext;C:\Windows\Sun\Java\lib\ext
    sun.boot.class.path = C:\Program Files\Java\jdk1.8.0_181\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\rt.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\sunrsasign.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_181\jre\classes
    java.vendor = Oracle Corporation
    file.separator = \
    java.vendor.url.bug = http://bugreport.sun.com/bugreport/
    sun.io.unicode.encoding = UnicodeLittle
    sun.cpu.endian = little
    sun.desktop = windows
    sun.cpu.isalist = amd64
    
    VM Flags:
    Non-default VM flags: -XX:CICompilerCount=3 -XX:InitialHeapSize=329252864 -XX:MaxHeapSize=5255462912 -XX:MaxNewSize=1751646208 -XX:MinHeapDeltaBytes=524288 -XX:NewSize=109576192 -XX:OldSize=219676672 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseFastUnorderedTimeStamps -XX:-UseLargePagesIndividualAllocation -XX:+UseParallelGC
    Command line:  -javaagent:D:\IntelliJ IDEA Community Edition 2020.1.2\lib\idea_rt.jar=49725:D:\IntelliJ IDEA Community Edition 2020.1.2\bin -Dfile.encoding=UTF-8

1.  jmap -heap pid（这个指令一般在生产环境不能使用；一般在开发和测试是可以使用的）
2.  jstat -gc pid

S0C    S1C    S0U    S1U      EC       EU        OC         OU       MC     MU    CCSC   CCSU   YGC     YGCT    FGC    FGCT     GCT
    13312.0 13312.0  0.0   7368.5 80384.0  31455.3   214528.0     80.0    14976.0 14475.0 1920.0 1730.8      1    0.008   0      0.000    0.008

S0C：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
    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
    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

1.  jstack pid (看堆栈信息)

2020-12-17 19:32:50
    Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.181-b13 mixed mode):
    
    "RemotingExecutorThread_8" #38 prio=5 os_prio=0 tid=0x0000000020d19800 nid=0x34a0 waiting on condition [0x00000000271df000]
       java.lang.Thread.State: WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075c801c60> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
            at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
            at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
            at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
            at java.lang.Thread.run(Thread.java:748)
    
    "RemotingExecutorThread_7" #37 prio=5 os_prio=0 tid=0x0000000020d1c000 nid=0x2a0c waiting on condition [0x0000000024bbf000]
       java.lang.Thread.State: WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075c801c60> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
            at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
            at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
            at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
            at java.lang.Thread.run(Thread.java:748)
    
    "RemotingExecutorThread_6" #36 prio=5 os_prio=0 tid=0x0000000020d20800 nid=0x7f0 waiting on condition [0x00000000005ce000]
       java.lang.Thread.State: WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075c801c60> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
            at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
            at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
            at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
            at java.lang.Thread.run(Thread.java:748)
    
    "RemotingExecutorThread_5" #35 prio=5 os_prio=0 tid=0x0000000020d1f800 nid=0x890 waiting on condition [0x000000000211f000]
       java.lang.Thread.State: WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075c801c60> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
            at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
            at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
            at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
            at java.lang.Thread.run(Thread.java:748)
    
    "RemotingExecutorThread_4" #34 prio=5 os_prio=0 tid=0x0000000020d17800 nid=0x2e04 waiting on condition [0x00000000007ce000]
       java.lang.Thread.State: WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075c801c60> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
            at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
            at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
            at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
            at java.lang.Thread.run(Thread.java:748)
    
    "RemotingExecutorThread_3" #33 prio=5 os_prio=0 tid=0x0000000020d19000 nid=0x2f10 waiting on condition [0x00000000270de000]
       java.lang.Thread.State: WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075c801c60> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
            at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
            at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
            at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
            at java.lang.Thread.run(Thread.java:748)
    
    "RemotingExecutorThread_2" #32 prio=5 os_prio=0 tid=0x0000000020d1c800 nid=0x2fbc waiting on condition [0x0000000025fcf000]
       java.lang.Thread.State: WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075c801c60> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
            at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
            at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
            at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
            at java.lang.Thread.run(Thread.java:748)
    
    "NettyServerCodecThread_2" #21 prio=5 os_prio=0 tid=0x0000000020d18000 nid=0x25c0 waiting on condition [0x0000000024ebe000]
       java.lang.Thread.State: TIMED_WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075ca830d0> (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.LinkedBlockingQueue.poll(LinkedBlockingQueue.java:467)
            at io.netty.util.concurrent.SingleThreadEventExecutor.takeTask(SingleThreadEventExecutor.java:269)
            at io.netty.util.concurrent.DefaultEventExecutor.run(DefaultEventExecutor.java:39)
            at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:140)
            at java.lang.Thread.run(Thread.java:748)
    
    "NettyServerNIOSelector_3_2" #16 prio=5 os_prio=0 tid=0x0000000020d1e000 nid=0x2750 runnable [0x0000000024dbe000]
       java.lang.Thread.State: RUNNABLE
            at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)
            at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296)
            at sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278)
            at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159)
            at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
            - locked <0x000000075c92a2f0> (a io.netty.channel.nio.SelectedSelectionKeySet)
            - locked <0x000000075c92c370> (a java.util.Collections$UnmodifiableSet)
            - locked <0x000000075c92a220> (a sun.nio.ch.WindowsSelectorImpl)
            at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
            at io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:760)
            at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:401)
            at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:140)
            at java.lang.Thread.run(Thread.java:748)
    
    "RemotingExecutorThread_1" #31 prio=5 os_prio=0 tid=0x0000000020d1d800 nid=0x8b8 waiting on condition [0x0000000023aaf000]
       java.lang.Thread.State: WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075c801c60> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
            at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
            at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
            at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
            at java.lang.Thread.run(Thread.java:748)
    
    "threadDeathWatcher-2-1" #30 daemon prio=1 os_prio=-2 tid=0x000000002027d000 nid=0x3500 runnable [0x000000002279f000]
       java.lang.Thread.State: RUNNABLE
            at java.lang.Thread.isAlive(Native Method)
            at io.netty.util.ThreadDeathWatcher$Watcher.notifyWatchees(ThreadDeathWatcher.java:205)
            at io.netty.util.ThreadDeathWatcher$Watcher.run(ThreadDeathWatcher.java:143)
            at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:144)
            at java.lang.Thread.run(Thread.java:748)
    
    "NettyServerCodecThread_1" #20 prio=5 os_prio=0 tid=0x000000002027c000 nid=0x874 waiting on condition [0x000000002269f000]
       java.lang.Thread.State: WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075ca83590> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
            at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
            at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
            at io.netty.util.concurrent.SingleThreadEventExecutor.takeTask(SingleThreadEventExecutor.java:256)
            at io.netty.util.concurrent.DefaultEventExecutor.run(DefaultEventExecutor.java:39)
            at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:140)
            at java.lang.Thread.run(Thread.java:748)
    
    "NettyServerNIOSelector_3_1" #15 prio=5 os_prio=0 tid=0x000000002027b800 nid=0x321c runnable [0x000000002259e000]
       java.lang.Thread.State: RUNNABLE
            at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)
            at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296)
            at sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278)
            at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159)
            at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
            - locked <0x000000075c931100> (a io.netty.channel.nio.SelectedSelectionKeySet)
            - locked <0x000000075c934080> (a java.util.Collections$UnmodifiableSet)
            - locked <0x000000075c931030> (a sun.nio.ch.WindowsSelectorImpl)
            at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
            at io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:760)
            at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:401)
            at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:140)
            at java.lang.Thread.run(Thread.java:748)
    
    "DestroyJavaVM" #29 prio=5 os_prio=0 tid=0x000000002027a000 nid=0x3428 waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "FileWatchService" #28 prio=5 os_prio=0 tid=0x000000002027e800 nid=0x504 waiting on condition [0x000000002249f000]
       java.lang.Thread.State: TIMED_WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075ca84750> (a org.apache.rocketmq.common.CountDownLatch2$Sync)
            at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedNanos(AbstractQueuedSynchronizer.java:1037)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireSharedNanos(AbstractQueuedSynchronizer.java:1328)
            at org.apache.rocketmq.common.CountDownLatch2.await(CountDownLatch2.java:114)
            at org.apache.rocketmq.common.ServiceThread.waitForRunning(ServiceThread.java:139)
            at org.apache.rocketmq.srvutil.FileWatchService.run(FileWatchService.java:70)
            at java.lang.Thread.run(Thread.java:748)
    
    "NettyEventExecutor" #12 prio=5 os_prio=0 tid=0x000000002027d800 nid=0x2388 waiting on condition [0x000000002239f000]
       java.lang.Thread.State: TIMED_WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075c801af0> (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.LinkedBlockingQueue.poll(LinkedBlockingQueue.java:467)
            at org.apache.rocketmq.remoting.netty.NettyRemotingAbstract$NettyEventExecutor.run(NettyRemotingAbstract.java:587)
            at java.lang.Thread.run(Thread.java:748)
    
    "NettyNIOBoss_1" #14 prio=5 os_prio=0 tid=0x000000002027f000 nid=0x1d2c runnable [0x000000002229e000]
       java.lang.Thread.State: RUNNABLE
            at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)
            at sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(WindowsSelectorImpl.java:296)
            at sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(WindowsSelectorImpl.java:278)
            at sun.nio.ch.WindowsSelectorImpl.doSelect(WindowsSelectorImpl.java:159)
            at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
            - locked <0x000000075c903960> (a io.netty.channel.nio.SelectedSelectionKeySet)
            - locked <0x000000075c9059e0> (a java.util.Collections$UnmodifiableSet)
            - locked <0x000000075c903880> (a sun.nio.ch.WindowsSelectorImpl)
            at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
            at io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:760)
            at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:401)
            at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:140)
            at java.lang.Thread.run(Thread.java:748)
    
    "NSScheduledThread1" #18 prio=5 os_prio=0 tid=0x0000000020278800 nid=0x1cd4 waiting on condition [0x000000002219e000]
       java.lang.Thread.State: TIMED_WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075c800e88> (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:1074)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
            at java.lang.Thread.run(Thread.java:748)
    
    "ServerHouseKeepingService" #13 daemon prio=5 os_prio=0 tid=0x0000000020279000 nid=0x2110 in Object.wait() [0x0000000021a9f000]
       java.lang.Thread.State: TIMED_WAITING (on object monitor)
            at java.lang.Object.wait(Native Method)
            at java.util.TimerThread.mainLoop(Timer.java:552)
            - locked <0x000000075c808180> (a java.util.TaskQueue)
            at java.util.TimerThread.run(Timer.java:505)
    
    "AsyncAppender-Worker-Thread-0" #11 daemon prio=5 os_prio=0 tid=0x000000002051c800 nid=0x1984 waiting on condition [0x00000000209ce000]
       java.lang.Thread.State: WAITING (parking)
            at sun.misc.Unsafe.park(Native Method)
            - parking to wait for  <0x000000075c810180> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
            at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
            at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
            at java.util.concurrent.ArrayBlockingQueue.take(ArrayBlockingQueue.java:403)
            at ch.qos.logback.core.AsyncAppenderBase$Worker.run(AsyncAppenderBase.java:225)
    
    "Service Thread" #10 daemon prio=9 os_prio=0 tid=0x000000001f5ce000 nid=0x176c runnable [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "C1 CompilerThread2" #9 daemon prio=9 os_prio=2 tid=0x000000001f560800 nid=0x374c waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "C2 CompilerThread1" #8 daemon prio=9 os_prio=2 tid=0x000000001f54c800 nid=0x1964 waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "C2 CompilerThread0" #7 daemon prio=9 os_prio=2 tid=0x000000001f54a800 nid=0x3170 waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "Monitor Ctrl-Break" #6 daemon prio=5 os_prio=0 tid=0x000000001f547000 nid=0x3338 runnable [0x000000001fb1e000]
       java.lang.Thread.State: RUNNABLE
            at java.net.SocketInputStream.socketRead0(Native Method)
            at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
            at java.net.SocketInputStream.read(SocketInputStream.java:171)
            at java.net.SocketInputStream.read(SocketInputStream.java:141)
            at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
            at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
            at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
            - locked <0x000000075c81e850> (a java.io.InputStreamReader)
            at java.io.InputStreamReader.read(InputStreamReader.java:184)
            at java.io.BufferedReader.fill(BufferedReader.java:161)
            at java.io.BufferedReader.readLine(BufferedReader.java:324)
            - locked <0x000000075c81e850> (a java.io.InputStreamReader)
            at java.io.BufferedReader.readLine(BufferedReader.java:389)
            at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:61)
    
    "Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x000000001e124800 nid=0x240c waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x000000001f430800 nid=0x1290 runnable [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "Finalizer" #3 daemon prio=8 os_prio=1 tid=0x000000001e0bf000 nid=0x1fb0 in Object.wait() [0x000000001f41f000]
       java.lang.Thread.State: WAITING (on object monitor)
            at java.lang.Object.wait(Native Method)
            - waiting on <0x000000075c808608> (a java.lang.ref.ReferenceQueue$Lock)
            at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144)
            - locked <0x000000075c808608> (a java.lang.ref.ReferenceQueue$Lock)
            at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165)
            at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216)
    
    "Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x0000000002823000 nid=0x371c in Object.wait() [0x000000001f31f000]
       java.lang.Thread.State: WAITING (on object monitor)
            at java.lang.Object.wait(Native Method)
            - waiting on <0x000000075c8103d0> (a java.lang.ref.Reference$Lock)
            at java.lang.Object.wait(Object.java:502)
            at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
            - locked <0x000000075c8103d0> (a java.lang.ref.Reference$Lock)
            at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
    
    "VM Thread" os_prio=2 tid=0x000000001e097800 nid=0x3564 runnable
    
    "GC task thread#0 (ParallelGC)" os_prio=0 tid=0x0000000002749000 nid=0x93c runnable
    
    "GC task thread#1 (ParallelGC)" os_prio=0 tid=0x000000000274a800 nid=0x2324 runnable
    
    "GC task thread#2 (ParallelGC)" os_prio=0 tid=0x000000000274c000 nid=0x17a4 runnable
    
    "GC task thread#3 (ParallelGC)" os_prio=0 tid=0x000000000274d800 nid=0x3188 runnable
    
    "VM Periodic Task Thread" os_prio=2 tid=0x000000001f626800 nid=0x1e80 waiting on condition
    
    JNI global references: 222

1.  jconsole, jvisulvm （不允许远程连接生产环境。本地开发或者测试是可以连接的。）  
    一般把生产环境中**堆转储文件**加载到jvisulvm进行分析。

*  **arthas**（阿里开源工具使用） windows上使用

1.  java -jar arthas-boot.jar pid
2.  help

NAME         DESCRIPTION
     help         Display Arthas Help
     keymap       Display all the available keymap for the specified connection.
     sc           Search all the classes loaded by JVM
     sm           Search the method of classes loaded by JVM
     classloader  Show classloader info
     jad          Decompile class
     getstatic    Show the static field of a class
     monitor      Monitor method execution statistics, e.g. total/success/failure count, average rt, fail rate, etc.
     stack        Display the stack trace for the specified class and method
     thread       Display thread info, thread stack
     trace        Trace the execution time of specified method invocation.
     watch        Display the input/output parameter, return object, and thrown exception of specified method invocation
     tt           Time Tunnel
     jvm          Display the target JVM information
     perfcounter  Display the perf counter information.
     ognl         Execute ognl expression.
     mc           Memory compiler, compiles java files into bytecode and class files in memory.
     redefine     Redefine classes. @see Instrumentation#redefineClasses(ClassDefinition...)
     dashboard    Overview of target jvm's thread, memory, gc, vm, tomcat info.
     dump         Dump class byte array from JVM
     heapdump     Heap dump
     options      View and change various Arthas options
     cls          Clear the screen
     reset        Reset all the enhanced classes
     version      Display Arthas version
     session      Display current session information
     sysprop      Display, and change the system properties.
     sysenv       Display the system env.
     vmoption     Display, and update the vm diagnostic options.
     logger       Print logger info, and update the logger level
     history      Display command history
     cat          Concatenate and print files
     echo         write arguments to the standard output
     pwd          Return working directory name
     mbean        Display the mbean information
     grep         grep command for pipes.
     tee          tee command for pipes.
     profiler     Async Profiler. https://github.com/jvm-profiling-tools/async-profiler
     stop         Stop/Shutdown Arthas server and exit the console.

1.  thread

Threads Total: 44, NEW: 0, RUNNABLE: 12, BLOCKED: 0, WAITING: 14, TIMED_WAITING: 8, TERMINATED: 0, Internal threads: 10
    ID   NAME                          GROUP          PRIORITY  STATE    %CPU      DELTA_TIM TIME      INTERRUPT DAEMON
    2    Reference Handler             system         10        WAITING  0.0       0.000     0:0.000   false     true
    3    Finalizer                     system         8         WAITING  0.0       0.000     0:0.000   false     true
    4    Signal Dispatcher             system         9         RUNNABLE 0.0       0.000     0:0.000   false     true
    5    Attach Listener               system         5         RUNNABLE 0.0       0.000     0:0.031   false     true
    40   arthas-timer                  system         5         WAITING  0.0       0.000     0:0.000   false     true
    43   arthas-NettyHttpTelnetBootstr system         5         RUNNABLE 0.0       0.000     0:0.000   false     true
    44   arthas-NettyWebsocketTtyBoots system         5         RUNNABLE 0.0       0.000     0:0.000   false     true
    45   arthas-NettyWebsocketTtyBoots system         5         RUNNABLE 0.0       0.000     0:0.000   false     true
    46   arthas-shell-server           system         5         TIMED_WA 0.0       0.000     0:0.000   false     true
    47   arthas-session-manager        system         5         TIMED_WA 0.0       0.000     0:0.000   false     true
    48   arthas-UserStat               system         5         WAITING  0.0       0.000     0:0.000   false     true
    50   arthas-NettyHttpTelnetBootstr system         5         RUNNABLE 0.0       0.000     0:0.078   false     true
    51   arthas-command-execute        system         5         RUNNABLE 0.0       0.000     0:0.000   false     true
    6    Monitor Ctrl-Break            main           5         RUNNABLE 0.0       0.000     0:0.015   false     true
    11   AsyncAppender-Worker-Thread-0 main           5         WAITING  0.0       0.000     0:0.015   false     true
    13   ServerHouseKeepingService     main           5         TIMED_WA 0.0       0.000     0:0.000   false     true
    18   NSScheduledThread1            main           5         TIMED_WA 0.0       0.000     0:0.000   false     false
    14   NettyNIOBoss_1                main           5         RUNNABLE 0.0       0.000     0:0.046   false     false
    12   NettyEventExecutor            main           5         TIMED_WA 0.0       0.000     0:0.000   false     false
    28   FileWatchService              main           5         TIMED_WA 0.0       0.000     0:0.015   false     false
    29   DestroyJavaVM                 main           5         RUNNABLE 0.0       0.000     0:1.625   false     false
    15   NettyServerNIOSelector_3_1    main           5         RUNNABLE 0.0       0.000     0:0.046   false     false
    20   NettyServerCodecThread_1      main           5         WAITING  0.0       0.000     0:0.140   false     false
    30   threadDeathWatcher-2-1        main           1         TIMED_WA 0.0       0.000     0:0.015   false     true
    31   RemotingExecutorThread_1      main           5         WAITING  0.0       0.000     0:0.078   false     false
    16   NettyServerNIOSelector_3_2    main           5         RUNNABLE 0.0       0.000     0:0.203   false     false
    21   NettyServerCodecThread_2      main           5         TIMED_WA 0.0       0.000     0:0.578   false     false

1.  thread -b （查询是否有线程发生死锁）如果没有发生则打印如下信息  
    用处：定位业务代码中，哪些线程发送了死锁。然后，仔细阅读那部分业务代码即可。

No most blocking thread found!

1.  dashboard

ID   NAME                          GROUP          PRIORITY  STATE    %CPU      DELTA_TIM TIME      INTERRUPT DAEMON
    -1   C1 CompilerThread2            -              -1        -        0.0       0.000     0:1.875   false     true
    -1   C2 CompilerThread0            -              -1        -        0.0       0.000     0:1.750   false     true
    29   DestroyJavaVM                 main           5         RUNNABLE 0.0       0.000     0:1.625   false     false
    -1   C2 CompilerThread1            -              -1        -        0.0       0.000     0:1.562   false     true
    21   NettyServerCodecThread_2      main           5         TIMED_WA 0.0       0.000     0:0.640   false     false
    50   arthas-NettyHttpTelnetBootstr system         5         RUNNABLE 0.0       0.000     0:0.265   false     true
    16   NettyServerNIOSelector_3_2    main           5         RUNNABLE 0.0       0.000     0:0.218   false     false
    20   NettyServerCodecThread_1      main           5         WAITING  0.0       0.000     0:0.140   false     false
    32   RemotingExecutorThread_2      main           5         WAITING  0.0       0.000     0:0.093   false     false
    51   arthas-command-execute        system         5         RUNNABLE 0.0       0.000     0:0.078   false     true
    31   RemotingExecutorThread_1      main           5         WAITING  0.0       0.000     0:0.078   false     false
    Memory                    used    total    max     usage    GC
    heap                      67M     180M     4455M   1.52%    gc.ps_scavenge.count          2
    ps_eden_space             57M     78M      1644M   3.49%    gc.ps_scavenge.time(ms)       25
    ps_survivor_space         0K      13312K   13312K  0.00%    gc.ps_marksweep.count         1
    ps_old_gen                10M     89M      3341M   0.31%    gc.ps_marksweep.time(ms)      36
    nonheap                   35M     38M      -1      90.93%
    code_cache                5M      8M       240M    2.40%
    metaspace                 26M     27M      -1      97.20%
    compressed_class_space    3M      3M       1024M   0.31%
    Runtime
    os.name                                                     Windows 10
    os.version                                                  10.0
    java.version                                                1.8.0_181
    java.home                                                   C:\Program Files\Java\jdk1.8.0_181\jre
    systemload.average                                          -1.00
    processors                                                  4
    timestamp/uptime                                            Thu Dec 17 19:57:59 CST 2020/2307s

*  **调优实战过程的注意事项**

1.  启动应用服务的时候，需要添加上，**-XX:+HeapDumpOnOutOfMemeryError**
2.  jmap -heap pid 不能直接在生产环境中使用，只能在开发和测试环境中使用。
3.  采用jvisulvm工具，把发生OOM的时候，dump的文件，加载进来，进行分析，定位问题。
4.  生产环境，可以直接使用**arthas**工具，采集自己需要的信息。比如定位线程死锁。比如定位哪个线程消耗了大量的CPU资源。

#### 小结 ####

*  能够熟练定位jvm相关问题，并能够分析相关信息，定位问题。读代码，找到问题原因，解决问题。
 *  理解这些基础指令。不要记忆。需要的时候，可以查询。也可以使用hlep指令，查询。