Java 与 C++ 之间有一堵由内存动态分配和垃圾收集技术所围成的高强,墙外面的人想进去,墙里面的人想出来.
4.1 概述
理论总是作为指导实践的工具,能把这些知识应用到实际工作中才是我们的最终目的.
给一个系统定位问题的时候,知识/经验是关键基础, 数据是依据, 工具是运用知识处理数据的手段.
数据包括: 运行日志, 异常堆栈, GC日志, 线程快照, 堆转储快照等.
经常使用适当的虚拟机监控和分析的工具可以加快我们分析数据,定位解决问题的速度.
4.2 JDK的命令行工具
JDK的bin目录
表:Sun JDK 监控和故障处理工具
| 名称 | 主要作用 |
|---|---|
| jps | JVM Process Status Tool, 显示指定系统内所有的HotSpot 虚拟机进程 |
| jstat | JVM Statistics Monitoring Tool, 用于收集 HotSpot 虚拟机各方面的运行数据 |
| jinfo | Configuration Info for Java, 显示虚拟机配置信息 |
| jmap | Memory Map for Java, 生成虚拟机的内存转储快照(headdump 文件) |
| jhat | JVM Heap Dump Browser, 用于分析heapdump 文件,它会建立一个HTTP/HTML 服务器, 让用户可以在浏览器上查看分析结果 |
| jstack | Stack Trace for Java, 显示虚拟机的线程快照 |
4.2.1 jps: 虚拟机进程状态工具
jps: 列出正在运行的虚拟机进程,并显示虚拟机执行主类(Main Class, main()函数所在的类)名称以及这些进程的本地虚拟机唯一ID(Local Virtual Machine Identifier, LVMID).
jps 命令格式: jps [options] [hostid]
jps 执行样例:
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jps -l
30096 blog-0.0.1-SNAPSHOT.jar
13242 sun.tools.jps.Jps
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jps -q
30096
13254
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jps -m
30096 jar
13266 Jps -m
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jps -v
30096 jar
13278 Jps -Denv.class.path=.:/usr/java/jdk1.8.0_161/lib:/usr/java/jdk1.8.0_161/jre/lib -Dapplication.home=/usr/java/jdk1.8.0_161 -Xms8m
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jps -lv
30096 blog-0.0.1-SNAPSHOT.jar
13292 sun.tools.jps.Jps -Denv.class.path=.:/usr/java/jdk1.8.0_161/lib:/usr/java/jdk1.8.0_161/jre/lib -Dapplication.home=/usr/java/jdk1.8.0_161 -Xms8m
表: jps 工具主要选项
| 选项 | 作用 |
|---|---|
| -q | 只输出 LVMID, 省略主类的名称 |
| -m | 输出虚拟机进程启动时传递给主类main() 函数的参数 |
| -l | 输出主类的全名, 如果进程执行的是Jar包,输出 Jar路径 |
| -v | 输出虚拟机进程启动时JVM参数 |
4.2.2 jstat: 虚拟机统计信息监视工具
jstat(JVM Statistics Monitoring Tool) 是用于监视虚拟机各种运行状态信息的命令行工具. 它可以显示本地或者远程虚拟机进程中的类装载,内存,垃圾收集,JIT编译等运行数据, 在没有GUI图形界面,只提供了纯文本控制台环境的服务器上,它将是运行期定位虚拟机性能问题的首选工具.
jstat 命令格式: jstat [option vmid [interval [s | ms] [count] ]]
假设需要每250毫秒查询一次进程2764的垃圾收集情况, 一共查询20次:
jstat -gc 2764 250 20
表: jstat 工具主要选项
| 选项 | 作用 |
|---|---|
| -class | 监视类装载,卸载数量,总空间以及类装载所耗费的时间 |
| -gc | 监视Java堆状况,包括Eden区, 两个Survivor区,老年代,永久代等的容量,已用空间,GC时间合计等信息 |
| -gccapacity | 监视内容与-gc基本相同,但输出主要专注Java堆各个区域使用到的最大,最小空间 |
| -gcutil | 监视内容与 -gc 基本相同, 但输出主要关注已使用空间占总空间的百分比 |
| -gccause | 与 -gcutil 功能一样,但是会额外输出导致上一次GC产生的原因 |
| -gcnew | 监视新生代GC状况 |
| -gcnewcapacity | 监视内容与 -gcnew 基本相同,输出主要关注使用到的最大,最小空间 |
| -gcold | 监视老年代GC状况 |
| -gcoldcapacity | 监视内容与i -gcold 基本相同,输出主要关注使用到的最大,最小空间 |
| -gcpermcapacity | 输出永久代使用到的最大,最小空间 |
| -compiler | 输出JIT 编译器编译过的方法,耗时等信息 |
| -printcompilation | 输出已经被JIT编译的方法 |
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jstat -class 30096
Loaded Bytes Unloaded Bytes Time
11647 21454.1 0 0.0 19.01
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jstat -gc 30096
S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT
2624.0 2624.0 100.6 0.0 21184.0 6007.8 52748.0 49099.7 65968.0 64808.9 8112.0 7844.3 378 2.038 3 0.311 2.349
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jstat -gccapacity 30096
NGCMN NGCMX NGC S0C S1C EC OGCMN OGCMX OGC OC MCMN MCMX MC CCSMN CCSMX CCSC YGC FGC
10880.0 171328.0 26432.0 2624.0 2624.0 21184.0 21888.0 342720.0 52748.0 52748.0 0.0 1107968.0 65968.0 0.0 1048576.0 8112.0 378 3
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jstat -gcutil 30096
S0 S1 E O M CCS YGC YGCT FGC FGCT GCT
3.84 0.00 28.36 93.08 98.24 96.70 378 2.038 3 0.311 2.349
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jstat -gccause 30096
S0 S1 E O M CCS YGC YGCT FGC FGCT GCT LGCC GCC
3.84 0.00 28.36 93.08 98.24 96.70 378 2.038 3 0.311 2.349 Allocation Failure No GC
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jstat -gcnew 30096
S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT
2624.0 2624.0 100.6 0.0 15 15 1312.0 21184.0 6007.8 378 2.038
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jstat -gcold 30096
MC MU CCSC CCSU OC OU YGC FGC FGCT GCT
65968.0 64808.9 8112.0 7844.3 52748.0 49099.7 378 3 0.311 2.349
linyk3@aliyun02:/usr/java/jdk1.8.0_161/bin$ jstat -compiler 30096
Compiled Failed Invalid Time FailedType FailedMethod
11317 1 0 58.19 1 com/mysql/jdbc/AbandonedConnectionCleanupThread run
4.2.3 jinfo: Java 配置信息工具
jinfo(Configuration Info for Java) 的作用是实时的查看和调整虚拟机各项参数.
jinfo 命令格式: jinfo [ option ] pid
执行样例:
linyk3@aliyun02:~$ jinfo -flag CMSInitiatingOccupancyFraction 30096
-XX:CMSInitiatingOccupancyFraction=-1
4.2.4 jmap : Java 内存映像工具
jmap(Memory Map for Java) 命令用于生成堆转储快照(一般称为 heapdump 或 dump 文件).
jmap 的作用不仅仅是为了获取dump文件,它还可以查询finalize执行队列, Java堆和永久代的详细信息,如空间使用率,当前使用的是哪种收集器等.
jmap 命令格式: jmap [ option ] vmid
表: jmap 工具的主要选项
| 选项 | 作用 |
|---|---|
| -dump | 生成Java堆转储快照. 格式为 -dump:[live, ] format=b, file= |
| -finalizerinfo | 显示在F-Queue 中等待 Finalizer 线程执行 finalize 方法的对象. 只在 Linux/Solaris 平台下有效 |
| -heap | 显示Java堆详细信息, 如使用何种收集器,参数配置,分代状况等.只在Linux/Solaris平台下有效 |
| -histo | 显示堆中对象统计信息, 包括类,实列对象,合计容量 |
| -permstat | 以ClassLoader 为统计口径显示永久代内存状态. 只在Linux/Solaris平台下有效 |
| -F | 当虚拟机进程对 -dump 选项没有响应时, 可使用这个选项强制生成 dump 快照. 只在 Linux/Solaris 平台下有效 |
linyk3@aliyun02:~$ jps -l
30096 blog-0.0.1-SNAPSHOT.jar
16257 sun.tools.jps.Jps
linyk3@aliyun02:~$
linyk3@aliyun02:~$ jmap -dump:format=b,file=blog.bin 30096
Dumping heap to /home/linyk3/blog.bin ...
Heap dump file created
linyk3@aliyun02:~$
4.2.5 jhat: 虚拟机堆转储快照分析工具
Sun JDK 提供 jhat(JVM Heap Analysis Tool) 命令与 jmap 搭配使用,来分析jmap 生成的堆转储快照.
linyk3@aliyun02:~$ jhat blog
blog/ blog.bin
linyk3@aliyun02:~$ jhat blog.bin
Reading from blog.bin...
Dump file created Tue Jan 21 00:59:03 CST 2020
Snapshot read, resolving...
Resolving 1125167 objects...
Chasing references, expect 225 dots.................................................................................................................................................................................................................................
Eliminating duplicate references.................................................................................................................................................................................................................................
Snapshot resolved.
Started HTTP server on port 7000
Server is ready.
当 提示"Server is ready" 时, 访问服务器http://locolhost:7000/ 就可以看到分析结果了
image.png
分析内存泄漏只要是用到其中的 "heap histogram"
image.png
image.png
image.png
4.2.6 jstack : Java 堆栈跟踪工具
jstack(Stack Trace for Java)命令用于生成虚拟机挡墙时刻的线程快照(一般称为threaddump或者javacore文件).
线程快照就是当前虚拟机内每一条线程正在执行的方法堆栈的集合,生成线程快照的主要目的就是定位线程出现长时间停顿的原因,如线程间锁死, 死循环, 请求外部资源导致的长时间等待等都是导致线程长时间停顿的常见原因.
线程出现停顿的时候,通过jstack来查看各个线程的调用堆栈,就可以知道没有响应的线程到底在后台做些什么事, 或者等待着什么资源.
jstack 命令格式: jstack [ option ] vmid
表: jstack 工具主要选项
| 选项 | 作用 |
|---|---|
| -F | 当正常输出的请求不被响应时, 强制输出线程堆栈 |
| -l | 除堆栈外,显示关于锁的附加消息 |
| -m | 如果调用到本地方法的话, 可以显示C/C++的堆栈 |
linyk3@aliyun02:~$ jstack -l 30096
2020-01-21 01:20:55
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.161-b12 mixed mode):
"Attach Listener" #34 daemon prio=9 os_prio=0 tid=0x00007f503802b000 nid=0x3eed waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"logback-1" #33 daemon prio=5 os_prio=0 tid=0x00007f5034558000 nid=0x75d2 waiting on condition [0x00007f502bbbc000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000edb37bd8> (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.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1081)
at java.util.concurrent.ScheduledThreadPoolExecutor$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$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"DestroyJavaVM" #32 prio=5 os_prio=0 tid=0x00007f505c00a800 nid=0x7592 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"http-nio-9001-AsyncTimeout" #30 daemon prio=5 os_prio=0 tid=0x00007f505e36d800 nid=0x75c9 waiting on condition [0x00007f502bebd000]
java.lang.Thread.State: TIMED_WAITING (sleeping)
at java.lang.Thread.sleep(Native Method)
at org.apache.coyote.AbstractProtocol$AsyncTimeout.run(AbstractProtocol.java:1211)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"http-nio-9001-Acceptor-0" #29 daemon prio=5 os_prio=0 tid=0x00007f505e8ad000 nid=0x75c8 runnable [0x00007f502bfbe000]
java.lang.Thread.State: RUNNABLE
at sun.nio.ch.ServerSocketChannelImpl.accept0(Native Method)
at sun.nio.ch.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:422)
at sun.nio.ch.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:250)
- locked <0x00000000ed9fead0> (a java.lang.Object)
at org.apache.tomcat.util.net.NioEndpoint$Acceptor.run(NioEndpoint.java:455)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"http-nio-9001-ClientPoller-0" #28 daemon prio=5 os_prio=0 tid=0x00007f505d103800 nid=0x75c7 runnable [0x00007f502c0bf000]
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 <0x00000000eda5c8a0> (a sun.nio.ch.Util$3)
- locked <0x00000000eda5c8b0> (a java.util.Collections$UnmodifiableSet)
- locked <0x00000000eda5c858> (a sun.nio.ch.EPollSelectorImpl)
at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
at org.apache.tomcat.util.net.NioEndpoint$Poller.run(NioEndpoint.java:787)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"http-nio-9001-exec-10" #27 daemon prio=5 os_prio=0 tid=0x00007f505ca4d000 nid=0x75c6 waiting on condition [0x00007f502c1c0000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ed9feae0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"http-nio-9001-exec-9" #26 daemon prio=5 os_prio=0 tid=0x00007f505e79e800 nid=0x75c5 waiting on condition [0x00007f502c2c1000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ed9feae0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"http-nio-9001-exec-8" #25 daemon prio=5 os_prio=0 tid=0x00007f505c15a800 nid=0x75c4 waiting on condition [0x00007f502c3c2000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ed9feae0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"http-nio-9001-exec-7" #24 daemon prio=5 os_prio=0 tid=0x00007f505c9df800 nid=0x75c3 waiting on condition [0x00007f502c4c3000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ed9feae0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"http-nio-9001-exec-6" #23 daemon prio=5 os_prio=0 tid=0x00007f505d03f800 nid=0x75c2 waiting on condition [0x00007f502c5c4000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ed9feae0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"http-nio-9001-exec-5" #22 daemon prio=5 os_prio=0 tid=0x00007f505e51e000 nid=0x75c1 waiting on condition [0x00007f502c6c5000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ed9feae0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"http-nio-9001-exec-4" #21 daemon prio=5 os_prio=0 tid=0x00007f505e5a3000 nid=0x75c0 waiting on condition [0x00007f502c7c6000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ed9feae0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"http-nio-9001-exec-3" #20 daemon prio=5 os_prio=0 tid=0x00007f505c387000 nid=0x75bf waiting on condition [0x00007f502c8c7000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ed9feae0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"http-nio-9001-exec-2" #19 daemon prio=5 os_prio=0 tid=0x00007f505c386000 nid=0x75be waiting on condition [0x00007f502c9c8000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ed9feae0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"http-nio-9001-exec-1" #18 daemon prio=5 os_prio=0 tid=0x00007f505c333000 nid=0x75bd waiting on condition [0x00007f504c1fd000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000000ed9feae0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"NioBlockingSelector.BlockPoller-1" #17 daemon prio=5 os_prio=0 tid=0x00007f505cdb6000 nid=0x75bc runnable [0x00007f502e0cd000]
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 <0x00000000ed9fed78> (a sun.nio.ch.Util$3)
- locked <0x00000000ed9fed88> (a java.util.Collections$UnmodifiableSet)
- locked <0x00000000ed9fed30> (a sun.nio.ch.EPollSelectorImpl)
at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
at org.apache.tomcat.util.net.NioBlockingSelector$BlockPoller.run(NioBlockingSelector.java:339)
Locked ownable synchronizers:
- None
"Abandoned connection cleanup thread" #16 daemon prio=5 os_prio=0 tid=0x00007f505cd44800 nid=0x75a4 in Object.wait() [0x00007f502dac9000]
java.lang.Thread.State: TIMED_WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
- locked <0x00000000ec550f60> (a java.lang.ref.ReferenceQueue$Lock)
at com.mysql.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:64)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- <0x00000000ec550ff0> (a java.util.concurrent.ThreadPoolExecutor$Worker)
"Tomcat JDBC Pool Cleaner[1804094807:1576085386247]" #15 daemon prio=5 os_prio=0 tid=0x00007f505ccfe800 nid=0x75a3 in Object.wait() [0x00007f502dbca000]
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 <0x00000000ec5511a0> (a java.util.TaskQueue)
at java.util.TimerThread.run(Timer.java:505)
Locked ownable synchronizers:
- None
"container-0" #14 prio=5 os_prio=0 tid=0x00007f505cb90800 nid=0x75a2 waiting on condition [0x00007f502decb000]
java.lang.Thread.State: TIMED_WAITING (sleeping)
at java.lang.Thread.sleep(Native Method)
at org.apache.catalina.core.StandardServer.await(StandardServer.java:427)
at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainer$1.run(TomcatEmbeddedServletContainer.java:177)
Locked ownable synchronizers:
- None
"ContainerBackgroundProcessor[StandardEngine[Tomcat]]" #13 daemon prio=5 os_prio=0 tid=0x00007f505cb92000 nid=0x75a1 waiting on condition [0x00007f502dfcc000]
java.lang.Thread.State: TIMED_WAITING (sleeping)
at java.lang.Thread.sleep(Native Method)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1355)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- None
"Service Thread" #7 daemon prio=9 os_prio=0 tid=0x00007f505c0dc000 nid=0x7599 runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"C1 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007f505c0d8800 nid=0x7598 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007f505c0d6800 nid=0x7597 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"Signal Dispatcher" #4 daemon prio=9 os_prio=0 tid=0x00007f505c0d2800 nid=0x7596 runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007f505c0a2000 nid=0x7595 in Object.wait() [0x00007f504cd24000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
- locked <0x00000000eb17c9c0> (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)
Locked ownable synchronizers:
- None
"Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007f505c09d800 nid=0x7594 in Object.wait() [0x00007f504ce25000]
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 <0x00000000eb17cb78> (a java.lang.ref.Reference$Lock)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
Locked ownable synchronizers:
- None
"VM Thread" os_prio=0 tid=0x00007f505c096000 nid=0x7593 runnable
"VM Periodic Task Thread" os_prio=0 tid=0x00007f505c0e1000 nid=0x759a waiting on condition
JNI global references: 289
linyk3@aliyun02:~$
4.2.7 HSDIS: JIT 生成代码反汇编
在Java虚拟机规范中, 详细描述了虚拟机指令集中每条指令的执行过程,执行前后对操作数栈,局部变量表的影响等细节.
分析程序如何执行,通过软件调试工具(GDB, Windbg)来断点调试是最常见的手段.但是在调试Java虚拟机会遇到很大困难.
HSDIS 是一个 Sun 官方推荐的 HotSpot 虚拟机 JIT 编译代码的反汇编插件.它的作用是让HotSpot的-XX:+PrintAssembly 指令调用它来把动态生成的本地代码还原为汇编代码输出,同时还生成大量非常有价值的注释,这样我们就可以通过输出的代码来分析问题.
4.3 JDK 可视化工具
JDK中除了提供大量的命令行工具,还有两个功能强大的可视化工具: JConsole 和 VisualVM.
JConsole: JDK 1.5 就以及提供的虚拟机监控工具
VisualVM: JDK1.6 Update7中才首次发布. 现在已经成为主力推动的多合一故障处理工具.
4.3.1 JConsole: Java 监视与管理控制台
-
启动:
image.png
4.3.2 VisualVM: 多合一故障处理工具
VisualVM(All-In-One Java Troubleshooting Tool)是到目前为止随JDK发布的功能最强大的运行监视和故障处理程序.
VisualVM 基于 NetBeans 平台开发, 所以具备了插件扩展功能:
-
- 显示虚拟机进程以及进程的配置,环境信息(jps, jinfo)
- 2.监视应用程序的CPU, GC, 堆, 方法区以及线程的信息(jstat, jstack)
- 3.dump 以及分析堆转储快照(jmap, jhat)
- 4.方法级的程序运行性能分析,找出被调用最多,运行时间最长的方法
- 5.离线程序快照: 手机程序的运行时配置, 线程dump, 内存 dump等信息建立一个快照, 可以将快照发送开发者进行bug反馈.
- 6.其他 plugins 的无限可能性
image.png
image.png
4.4 本章小结
本章介绍了随JDK发布的6个命令行工具以及两个可视化的故障处理工具,灵活使用这些工具可以给问题处理带来很大的便利.
除了JDK自带的工具外,常用的故障处理工具还有很多.