1、JVM的参数类型
1.1 标准参数：在各jdk版本中较稳定
-help
-server -client
-version -showversion
-cp -classpath
1.2 X参数
1.2.1非标准化参数
1.2.2 -Xint：完全解释执行
调整为完全解释执行编译模式：
MacBook-Pro:dubbo-learn chuanzhou$ java -Xint -version
java version "1.8.0_161"
Java(TM) SE Runtime Environment (build 1.8.0_161-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.161-b12, interpreted mode)
1.2.3 -Xcomp：第一次使用就编译成本地代码
调整为编译执行编译模式：
MacBook-Pro:dubbo-learn chuanzhou$ java -Xcomp -version
java version "1.8.0_161"
Java(TM) SE Runtime Environment (build 1.8.0_161-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.161-b12, compiled mode)
1.2.4 -Xmixed：混合模式，JVM自己来决定是否编译成本地代码
MacBook-Pro:~ chuanzhou$ java -version
java version "1.8.0_161"
Java(TM) SE Runtime Environment (build 1.8.0_161-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.161-b12, mixed mode)
最后一行的mixed mode表明JVM默认使用的编译模式是混合模式
1.3 XX参数
使用最多的一种参数类型
1.3.1 Boolean类型
格式：-XX:[+/-] <name> 表示启用或者禁用name属性
比如：
-XX:+UseConcMarkSweepGC 表示启用CMS垃圾回收器
-XX:+UseG1GC 表示启用G1垃圾回收器
1.3.2 非Boolean类型
格式：-XX:<name> = <value> 表示name属性的值为value
比如：
-XX:MaxGCPauseMillis=500 表示GC最大停顿时间是500毫秒
-XX:GCTimeRatio=19 表示...
1.3.3 -Xmx -Xms
虽然1以X开头，但是不是X类型参数，而是XX类型的参数
- -Xmx等价于-XX:MaxHeapSize 表示最大堆内存大小，可使用
jinfo -flag MaxHeapSize 进程id查看，如下：
[root@izwz93osmk5vi5qwqyscxaz bin]# ps -ef|grep java
root 9723 1 0 4月24 ? 04:28:59 /usr/program/jdk1.8.0_72/jre/bin/java -Djava.util.logging.config.file=/opt/tomcat/apache-tomcat-8.0.50/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dignore.endorsed.dirs= -classpath /opt/tomcat/apache-tomcat-8.0.50/bin/bootstrap.jar:/opt/tomcat/apache-tomcat-8.0.50/bin/tomcat-juli.jar -Dcatalina.base=/opt/tomcat/apache-tomcat-8.0.50 -Dcatalina.home=/opt/tomcat/apache-tomcat-8.0.50 -Djava.io.tmpdir=/opt/tomcat/apache-tomcat-8.0.50/temp org.apache.catalina.startup.Bootstrap start
root 20037 19984 0 20:53 pts/2 00:00:00 grep --color=auto java
[root@izwz93osmk5vi5qwqyscxaz bin]# ./jinfo -flag MaxHeapSize 9723
-XX:MaxHeapSize=482344960
[root@izwz93osmk5vi5qwqyscxaz bin]#
-
-Xms等价于-XX:InitalHeapSize 表示堆内存初始大小
-
-Xss等价于-XX:InitalStackSize 表示线程栈的初始大小，可以使用
jinfo -flag ThreadStackSize 进程id查看，如下：
[root@izwz93osmk5vi5qwqyscxaz bin]# ps -ef
[root@izwz93osmk5vi5qwqyscxaz bin]# ps -ef|grep java
root 9723 1 0 4月24 ? 04:28:59 /usr/program/jdk1.8.0_72/jre/bin/java -Djava.util.logging.config.file=/opt/tomcat/apache-tomcat-8.0.50/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dignore.endorsed.dirs= -classpath /opt/tomcat/apache-tomcat-8.0.50/bin/bootstrap.jar:/opt/tomcat/apache-tomcat-8.0.50/bin/tomcat-juli.jar -Dcatalina.base=/opt/tomcat/apache-tomcat-8.0.50 -Dcatalina.home=/opt/tomcat/apache-tomcat-8.0.50 -Djava.io.tmpdir=/opt/tomcat/apache-tomcat-8.0.50/temp org.apache.catalina.startup.Bootstrap start
root 20037 19984 0 20:53 pts/2 00:00:00 grep --color=auto java
[root@izwz93osmk5vi5qwqyscxaz bin]# ./jinfo -flag MaxHeapSize 9723
-XX:MaxHeapSize=482344960
[root@izwz93osmk5vi5qwqyscxaz bin]# ./jinfo -flag ThreadStackSize 9723
-XX:ThreadStackSize=1024
[root@izwz93osmk5vi5qwqyscxaz bin]#
2、JVM运行时参数查看
-XX:+printFlagsInitial查看JVM运行时初始值-XX:+printFlagsFinal查看JVM运行时最终值-XX:+UnlockExperimentalVMOptions解锁实验参数-XX:+UnlockDiagnosticVMOptions解锁诊断参数-XX:+PrintCommandLineFlags打印命令行参数
如查看JVM版本信息：java -XX:+PrintFlagsFinal -version > ~/version.txt
version.txt中部分参数：
[Global flags]
uintx AdaptiveSizeDecrementScaleFactor = 4 {product}
uintx AdaptiveSizeMajorGCDecayTimeScale = 10 {product}
uintx AdaptiveSizePausePolicy = 0 {product}
uintx AdaptiveSizePolicyCollectionCostMargin = 50 {product}
uintx AdaptiveSizePolicyInitializingSteps = 20 {product}
uintx AdaptiveSizePolicyOutputInterval = 0 {product}
uintx AdaptiveSizePolicyWeight = 10 {product}
uintx AdaptiveSizeThroughPutPolicy = 0 {product}
uintx AdaptiveTimeWeight = 25 {product}
bool AdjustConcurrency = false {product}
bool AggressiveOpts = false {product}
bool C1ProfileVirtualCalls = true {C1 product}
bool C1UpdateMethodData = true {C1 product}
intx CICompilerCount := 2 {product}
bool CICompilerCountPerCPU = true {product}
bool CITime = false {product}
bool CMSAbortSemantics = false {product}
uintx CMSAbortablePrecleanMinWorkPerIteration = 100 {product}
intx CMSAbortablePrecleanWaitMillis = 100 {manageable}
uintx CMSBitMapYieldQuantum = 10485760
注：=表示默认值，=:表示修改后的值
jps：查看Java进程
[root@izwz93osmk5vi5qwqyscxaz bin]# ./jps
20160 Jps
9723 Bootstrap
[root@izwz93osmk5vi5qwqyscxaz bin]# ./jps -l
20170 sun.tools.jps.Jps
9723 org.apache.catalina.startup.Bootstrap
[root@izwz93osmk5vi5qwqyscxaz bin]#
关于jps等命令的详解，可参考此文档https://docs.oracle.com/javase/8/docs/technotes/tools/unix/index.html
jinfo：查看指定Java进程运行时参数
如查看一个java进程id为9723的tomcat服务最大堆内存大小
[root@izwz93osmk5vi5qwqyscxaz bin]# ps -ef|grep java
root 9723 1 0 4月24 ? 04:29:03 /usr/program/jdk1.8.0_72/jre/bin/java -Djava.util.logging.config.file=/opt/tomcat/apache-tomcat-8.0.50/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dignore.endorsed.dirs= -classpath /opt/tomcat/apache-tomcat-8.0.50/bin/bootstrap.jar:/opt/tomcat/apache-tomcat-8.0.50/bin/tomcat-juli.jar -Dcatalina.base=/opt/tomcat/apache-tomcat-8.0.50 -Dcatalina.home=/opt/tomcat/apache-tomcat-8.0.50 -Djava.io.tmpdir=/opt/tomcat/apache-tomcat-8.0.50/temp org.apache.catalina.startup.Bootstrap start
root 20187 20123 0 21:34 pts/2 00:00:00 grep --color=auto java
[root@izwz93osmk5vi5qwqyscxaz bin]# ./jinfo -flag MaxHeapSize 9723
-XX:MaxHeapSize=482344960
[root@izwz93osmk5vi5qwqyscxaz bin]#
查看一个进程的所有运行时参数：
[root@izwz93osmk5vi5qwqyscxaz bin]# ./jinfo -flags 9732
Attaching to process ID 9732, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.72-b15
Non-default VM flags: -XX:CICompilerCount=2
-XX:InitialHeapSize=31457280 -XX:MaxHeapSize=482344960
-XX:MaxNewSize=160759808 -XX:MinHeapDeltaBytes=196608
-XX:NewSize=10485760 -XX:OldSize=20971520
-XX:+UseCompressedClassPointers -XX:+UseCompressedOops
Command line: -Djava.util.logging.config.file=/opt/tomcat/apache-tomcat-8.0.50/conf/logging.properties
-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048
-Djava.protocol.handler.pkgs=org.apache.catalina.webresources
-Dignore.endorsed.dirs= -Dcatalina.base=/opt/tomcat/apache-tomcat-8.0.50
-Dcatalina.home=/opt/tomcat/apache-tomcat-8.0.50
-Djava.io.tmpdir=/opt/tomcat/apache-tomcat-8.0.50/temp
[root@izwz93osmk5vi5qwqyscxaz bin]#
Non-default VM flags表示手动赋值过的参数，其中有些是tomcat设置的
Command line：与Non-default VM flags
查看垃圾回收器信息
MacBook-Pro:dubbo-learn chuanzhou$ jinfo -flag UseConcMarkSweepGc 29159
no such flag 'UseConcMarkSweepGc'
MacBook-Pro:dubbo-learn chuanzhou$ jinfo -flag UseG1Gc 29159
no such flag 'UseG1Gc'
MacBook-Pro:dubbo-learn chuanzhou$ jinfo -flag UseParallelGc 29159
no such flag 'UseParallelGc'
3、jstat查看虚拟机统计信息
3.1 类装载
格式：jstat -class 进程id 每隔多少毫秒 一共输出多少次
如：查看一个进程id为29159的java进程，每隔1s输出，一共输出10次
MacBook-Pro:dubbo-learn chuanzhou$ jstat -class 29159 1000 10
Loaded Bytes Unloaded Bytes Time
3204 6088.2 0 0.0 2.14
3204 6088.2 0 0.0 2.14
3204 6088.2 0 0.0 2.14
3204 6088.2 0 0.0 2.14
3204 6088.2 0 0.0 2.14
3204 6088.2 0 0.0 2.14
3204 6088.2 0 0.0 2.14
3204 6088.2 0 0.0 2.14
3204 6088.2 0 0.0 2.14
3204 6088.2 0 0.0 2.14
- Loaded：表示类加载的个数
- Bytes：表示类加载的大小，单位为kb
- UnLoaded：表示类卸载的个数
- Bytes：表示类卸载的大小，单位为kb
- Time：表示类加载和卸载的时间
3.2 垃圾收集
要查看一个java进程的垃圾收集器信息，可使用jstat -gc 进程id 每隔多少毫秒 一共输出多少次
MacBook-Pro:dubbo-learn chuanzhou$ jstat -gc 29159 1000 3
S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT
5120.0 5120.0 4308.8 0.0 33280.0 17845.6 87552.0 88.0 18944.0 18304.7 2304.0 2144.9 2 0.014 0 0.000 0.014
5120.0 5120.0 4308.8 0.0 33280.0 17845.6 87552.0 88.0 18944.0 18304.7 2304.0 2144.9 2 0.014 0 0.000 0.014
5120.0 5120.0 4308.8 0.0 33280.0 17845.6 87552.0 88.0 18944.0 18304.7 2304.0 2144.9 2 0.014 0 0.000 0.014
S0C: Current survivor space 0 capacity (kB).表示survivor 0区的总大小
S1C: Current survivor space 1 capacity (kB).表示survivor 1区的总大小
S0U: Survivor space 0 utilization (kB).表示survivor 0区使用了的大小
S1U: Survivor space 1 utilization (kB).表示survivor 1区使用了的大小
EC: Current eden space capacity (kB).表示eden区总大小
EU: Eden space utilization (kB).表示eden区使用了的大小
OC: Current old space capacity (kB).表示old区总大小
OU: Old space utilization (kB).表示old区使用了的大小
MC: Metaspace capacity (kB).表示Metaspace区总大小
MU: Metacspace utilization (kB).表示Metaspace区使用了的大小
CCSC: Compressed class space capacity (kB).表示压缩类空间总量
CCSU: Compressed class space used (kB).表示压缩类空间使用量
YGC: Number of young generation garbage collection events.表示Young GC的次数
YGCT: Young generation garbage collection time.表示Young GC的时间
FGC: Number of full GC events.表示full GC的次数
FGCT: Full garbage collection time.表示full GC的时间
GCT: Total garbage collection time.表示总的 GC的时间
3.3 JIT编译
3.3.1 -compiler参数
MacBook-Pro:dubbo-learn chuanzhou$ jstat -compiler 29159 1000 5
Compiled Failed Invalid Time FailedType FailedMethod
1284 0 0 3.50 0
1284 0 0 3.50 0
1284 0 0 3.50 0
1284 0 0 3.50 0
1284 0 0 3.50 0
- Compiled：表示编译成功的方法数量
- Failed：表示编译失败的方法数量
- Invalid：表示编译无效的方法数量
- Time：编译所花费的时间
- FailedType：编译失败类型
- FailedMethod：编译失败方法
3.3.2 -printcompilation参数
4、jmap+MAT实战内存溢出
模拟内存溢出：
@RestController
public class MemoryController {
private List<User> userList = new ArrayList<User>();
private List<Class<?>> classList = new ArrayList<Class<?>>();
/**
* -Xmx32M -Xms32M
* */
@GetMapping("/heap")
public String heap() {
int i=0;
while(true) {
userList.add(new User(i++, UUID.randomUUID().toString()));
}
}
/**
* -XX:MetaspaceSize=32M -XX:MaxMetaspaceSize=32M
* */
@GetMapping("/nonheap")
public String nonheap() {
while(true) {
classList.addAll(Metaspace.createClasses());
}
}
}
package com.imooc.monitor_tuning.chapter2;
import java.util.ArrayList;
import java.util.List;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
/*
* https://blog.csdn.net/bolg_hero/article/details/78189621
* 继承ClassLoader是为了方便调用defineClass方法，因为该方法的定义为protected
* */
public class Metaspace extends ClassLoader {
public static List<Class<?>> createClasses() {
// 类持有
List<Class<?>> classes = new ArrayList<Class<?>>();
// 循环1000w次生成1000w个不同的类。
for (int i = 0; i < 10000000; ++i) {
ClassWriter cw = new ClassWriter(0);
// 定义一个类名称为Class{i}，它的访问域为public，父类为java.lang.Object，不实现任何接口
cw.visit(Opcodes.V1_1, Opcodes.ACC_PUBLIC, "Class" + i, null,
"java/lang/Object", null);
// 定义构造函数<init>方法
MethodVisitor mw = cw.visitMethod(Opcodes.ACC_PUBLIC, "<init>",
"()V", null, null);
// 第一个指令为加载this
mw.visitVarInsn(Opcodes.ALOAD, 0);
// 第二个指令为调用父类Object的构造函数
mw.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object",
"<init>", "()V");
// 第三条指令为return
mw.visitInsn(Opcodes.RETURN);
mw.visitMaxs(1, 1);
mw.visitEnd();
Metaspace test = new Metaspace();
byte[] code = cw.toByteArray();
// 定义类
Class<?> exampleClass = test.defineClass("Class" + i, code, 0, code.length);
classes.add(exampleClass);
}
return classes;
}
}
package com.imooc.monitor_tuning.chapter2;
public class User {
private int id;
private String name;
public User(int id, String name) {
super();
this.id = id;
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
设置启动参数：
启动参数
启动application，发现出现内存溢出
4.1 如何导出内存溢出映像文件
4.2 内存溢出自动导出
-XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=./
4.3 使用jmap命令手动导出
格式：jmap -dump:format=b,file=路径/heap.hprof 进程id
其他命令：jmap -heap 进程id 查看堆信息
[root@izwz93osmk5vi5qwqyscxaz bin]# ./jmap -heap 9723
Attaching to process ID 9723, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.72-b15
using thread-local object allocation.
Mark Sweep Compact GC
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 482344960 (460.0MB)
NewSize = 10485760 (10.0MB)
MaxNewSize = 160759808 (153.3125MB)
OldSize = 20971520 (20.0MB)
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 = 32178176 (30.6875MB)
used = 16081160 (15.336189270019531MB)
free = 16097016 (15.351310729980469MB)
49.97536218336303% used
Eden Space:
capacity = 28639232 (27.3125MB)
used = 16054760 (15.311012268066406MB)
free = 12584472 (12.001487731933594MB)
56.058626153103546% used
From Space:
capacity = 3538944 (3.375MB)
used = 26400 (0.025177001953125MB)
free = 3512544 (3.349822998046875MB)
0.7459852430555556% used
To Space:
capacity = 3538944 (3.375MB)
used = 0 (0.0MB)
free = 3538944 (3.375MB)
0.0% used
tenured generation:
capacity = 71221248 (67.921875MB)
used = 57115304 (54.469398498535156MB)
free = 14105944 (13.452476501464844MB)
80.19419148622613% used
27532 interned Strings occupying 3194040 bytes.
4.4 使用MAT分析映像文件
MAT分析
- Class Name：类名
- Objects：对象数量
- Shallow Heap：
- Retained Heap：占用的内存大小
右键查看com.imooc.monitor_tuning.chapter2.User的强引用
image.png
image.png
也可以查看对象树：
对象树
5、jstack实战死循环与死锁
格式：jstack 进程id
2018-09-05 07:59:21
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.72-b15 mixed mode):
"Attach Listener" #16 daemon prio=9 os_prio=0 tid=0x00007f3d9c001000 nid=0x521f waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
"localhost-startStop-1" #15 daemon prio=5 os_prio=0 tid=0x00007f3dac002800 nid=0x5208 runnable [0x00007f3da15d1000]
java.lang.Thread.State: RUNNABLE
at java.io.FileInputStream.readBytes(Native Method)
at java.io.FileInputStream.read(FileInputStream.java:255)
at sun.security.provider.SeedGenerator$URLSeedGenerator.getSeedBytes(SeedGenerator.java:539)
at sun.security.provider.SeedGenerator.generateSeed(SeedGenerator.java:144)
at sun.security.provider.SecureRandom$SeederHolder.<clinit>(SecureRandom.java:203)
at sun.security.provider.SecureRandom.engineNextBytes(SecureRandom.java:221)
- locked <0x00000000e3e90be0> (a sun.security.provider.SecureRandom)
at java.security.SecureRandom.nextBytes(SecureRandom.java:468)
- locked <0x00000000e3e910c0> (a java.security.SecureRandom)
at java.security.SecureRandom.next(SecureRandom.java:491)
at java.util.Random.nextInt(Random.java:329)
at org.apache.catalina.util.SessionIdGeneratorBase.createSecureRandom(SessionIdGeneratorBase.java:240)
at org.apache.catalina.util.SessionIdGeneratorBase.getRandomBytes(SessionIdGeneratorBase.java:174)
at org.apache.catalina.util.StandardSessionIdGenerator.generateSessionId(StandardSessionIdGenerator.java:34)
at org.apache.catalina.util.SessionIdGeneratorBase.generateSessionId(SessionIdGeneratorBase.java:167)
at org.apache.catalina.util.SessionIdGeneratorBase.startInternal(SessionIdGeneratorBase.java:260)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
- locked <0x00000000e3e90730> (a org.apache.catalina.util.StandardSessionIdGenerator)
at org.apache.catalina.session.ManagerBase.startInternal(ManagerBase.java:717)
at org.apache.catalina.session.StandardManager.startInternal(StandardManager.java:352)
- locked <0x00000000e42eefb0> (a org.apache.catalina.session.StandardManager)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
- locked <0x00000000e42eefb0> (a org.apache.catalina.session.StandardManager)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5339)
- locked <0x00000000ed3c6ca0> (a org.apache.catalina.core.StandardContext)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
- locked <0x00000000ed3c6ca0> (a org.apache.catalina.core.StandardContext)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:753)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:729)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:974)
at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1850)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
"Catalina-startStop-1" #14 daemon prio=5 os_prio=0 tid=0x00007f3dc4437000 nid=0x5207 waiting on condition [0x00007f3da16d2000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ed3c6fc0> (a java.util.concurrent.FutureTask)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.FutureTask.awaitDone(FutureTask.java:429)
at java.util.concurrent.FutureTask.get(FutureTask.java:191)
at org.apache.catalina.startup.HostConfig.deployWARs(HostConfig.java:766)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:436)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1580)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:322)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:95)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.util.LifecycleBase.setStateInternal(LifecycleBase.java:388)
- locked <0x00000000ed03ec38> (a org.apache.catalina.core.StandardHost)
at org.apache.catalina.util.LifecycleBase.setState(LifecycleBase.java:333)
- locked <0x00000000ed03ec38> (a org.apache.catalina.core.StandardHost)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:960)
- locked <0x00000000ed03ec38> (a org.apache.catalina.core.StandardHost)
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:871)
- locked <0x00000000ed03ec38> (a org.apache.catalina.core.StandardHost)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
- locked <0x00000000ed03ec38> (a org.apache.catalina.core.StandardHost)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1408)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1398)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
"NioBlockingSelector.BlockPoller-2" #13 daemon prio=5 os_prio=0 tid=0x00007f3dc4429800 nid=0x5206 runnable [0x00007f3da17d4000]
java.lang.Thread.State: RUNNABLE
at sun.nio.ch.EPollArrayWrapper.epollWait(Native Method)
at sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:269)
at sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:93)
at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
- locked <0x00000000ed3c75a8> (a sun.nio.ch.Util$2)
- locked <0x00000000ed3c75b8> (a java.util.Collections$UnmodifiableSet)
- locked <0x00000000ed3c7560> (a sun.nio.ch.EPollSelectorImpl)
at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
at org.apache.tomcat.util.net.NioBlockingSelector$BlockPoller.run(NioBlockingSelector.java:301)
"NioBlockingSelector.BlockPoller-1" #12 daemon prio=5 os_prio=0 tid=0x00007f3dc440e800 nid=0x5205 runnable [0x00007f3da18d5000]
java.lang.Thread.State: RUNNABLE
at sun.nio.ch.EPollArrayWrapper.epollWait(Native Method)
at sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:269)
at sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:93)
at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
- locked <0x00000000ed3c77e0> (a sun.nio.ch.Util$2)
- locked <0x00000000ed3c77f0> (a java.util.Collections$UnmodifiableSet)
- locked <0x00000000ed3c7798> (a sun.nio.ch.EPollSelectorImpl)
at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
at org.apache.tomcat.util.net.NioBlockingSelector$BlockPoller.run(NioBlockingSelector.java:301)
"GC Daemon" #11 daemon prio=2 os_prio=0 tid=0x00007f3dc4356800 nid=0x5204 in Object.wait() [0x00007f3dc81a0000]
java.lang.Thread.State: TIMED_WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000000ed0d57f0> (a sun.misc.GC$LatencyLock)
at sun.misc.GC$Daemon.run(GC.java:117)
- locked <0x00000000ed0d57f0> (a sun.misc.GC$LatencyLock)
"AsyncFileHandlerWriter-789451787" #10 daemon prio=5 os_prio=0 tid=0x00007f3dc4105000 nid=0x5203 waiting on condition [0x00007f3dc8338000]
java.lang.Thread.State: TIMED_WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ecec1210> (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.LinkedBlockingDeque.pollFirst(LinkedBlockingDeque.java:522)
at java.util.concurrent.LinkedBlockingDeque.poll(LinkedBlockingDeque.java:684)
at org.apache.juli.AsyncFileHandler$LoggerThread.run(AsyncFileHandler.java:153)
"Service Thread" #7 daemon prio=9 os_prio=0 tid=0x00007f3dc40b3800 nid=0x5201 runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
"C1 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007f3dc40b0800 nid=0x5200 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
"C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007f3dc40ae800 nid=0x51ff waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
"Signal Dispatcher" #4 daemon prio=9 os_prio=0 tid=0x00007f3dc40ad000 nid=0x51fe runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
"Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007f3dc407a000 nid=0x51fd in Object.wait() [0x00007f3dc893e000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000000ecec2320> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
- locked <0x00000000ecec2320> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)
"Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007f3dc4075000 nid=0x51fc in Object.wait() [0x00007f3dc8a3f000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000000ecec24d8> (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:502)
at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
- locked <0x00000000ecec24d8> (a java.lang.ref.Reference$Lock)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
"main" #1 prio=5 os_prio=0 tid=0x00007f3dc4009000 nid=0x51fa waiting on condition [0x00007f3dcc417000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ed3c7340> (a java.util.concurrent.FutureTask)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.FutureTask.awaitDone(FutureTask.java:429)
at java.util.concurrent.FutureTask.get(FutureTask.java:191)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:943)
- locked <0x00000000ecfb7038> (a org.apache.catalina.core.StandardEngine)
at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:262)
- locked <0x00000000ecfb7038> (a org.apache.catalina.core.StandardEngine)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
- locked <0x00000000ecfb7038> (a org.apache.catalina.core.StandardEngine)
at org.apache.catalina.core.StandardService.startInternal(StandardService.java:441)
- locked <0x00000000ecfb7038> (a org.apache.catalina.core.StandardEngine)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
- locked <0x00000000ecfa2330> (a org.apache.catalina.core.StandardService)
at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:789)
- locked <0x00000000ecf4e258> (a java.lang.Object)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
- locked <0x00000000ecf1c578> (a org.apache.catalina.core.StandardServer)
at org.apache.catalina.startup.Catalina.start(Catalina.java:641)
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:349)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:483)
"VM Thread" os_prio=0 tid=0x00007f3dc406d800 nid=0x51fb runnable
"VM Periodic Task Thread" os_prio=0 tid=0x00007f3dc40b7000 nid=0x5202 waiting on condition
JNI global references: 59
- localhost-startStop-1：线程名
- daemon：后台线程
- prio：优先级
- os_prio：系统优先级
- tid：线程id
- nid：操作系统id
- java.lang.Thread.State：线程状态；NEW-线程尚未启动， RUNNABLE- 线程运行中，BLOCKED-等待一个锁， WAITINH-等待另一个线程， TIMED_WAITING-限时等待另一个线程， TERMINATED-已退出
5.1 实战死循环
import java.util.ArrayList;
import java.util.List;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class CpuController {
/**
* 死循环
* */
@RequestMapping("/loop")
public List<Long> loop(){
String data = "{"data":[{"partnerid":]";
return getPartneridsFromJson(data);
}
private Object lock1 = new Object();
private Object lock2 = new Object();
/**
* 死锁
* */
@RequestMapping("/deadlock")
public String deadlock(){
new Thread(()->{
synchronized(lock1) {
try {Thread.sleep(1000);}catch(Exception e) {}
synchronized(lock2) {
System.out.println("Thread1 over");
}
}
}) .start();
new Thread(()->{
synchronized(lock2) {
try {Thread.sleep(1000);}catch(Exception e) {}
synchronized(lock1) {
System.out.println("Thread2 over");
}
}
}) .start();
return "deadlock";
}
public static List<Long> getPartneridsFromJson(String data){
//{"data":[{"partnerid":982,"count":"10000","cityid":"11"},{"partnerid":983,"count":"10000","cityid":"11"},{"partnerid":984,"count":"10000","cityid":"11"}]}
//上面是正常的数据
List<Long> list = new ArrayList<Long>(2);
if(data == null || data.length() <= 0){
return list;
}
int datapos = data.indexOf("data");
if(datapos < 0){
return list;
}
int leftBracket = data.indexOf("[",datapos);
int rightBracket= data.indexOf("]",datapos);
if(leftBracket < 0 || rightBracket < 0){
return list;
}
String partners = data.substring(leftBracket+1,rightBracket);
if(partners == null || partners.length() <= 0){
return list;
}
while(partners!=null && partners.length() > 0){
int idpos = partners.indexOf("partnerid");
if(idpos < 0){
break;
}
int colonpos = partners.indexOf(":",idpos);
int commapos = partners.indexOf(",",idpos);
if(colonpos < 0 || commapos < 0){
//partners = partners.substring(idpos+"partnerid".length());//1
continue;
}
String pid = partners.substring(colonpos+1,commapos);
if(pid == null || pid.length() <= 0){
//partners = partners.substring(idpos+"partnerid".length());//2
continue;
}
try{
list.add(Long.parseLong(pid));
}catch(Exception e){
//do nothing
}
partners = partners.substring(commapos);
}
return list;
}
}
访问/loop端点三次，然后使用top命令：
#导出线程堆栈
$ jstack 7930 > 7930.txt
#打印该进程下的线程
$ top -p 7930 -H
#将十进制线程id转换为16进制
$ printf "%x" 8247
2037
然后在导出的7930.txt文件中找到2037
死循环
访问/loop端点，制造死循环，使用jstack命令导出线程堆栈信息：
死锁
最后一行已提示：Found 1 deadlock