OpenJDK 11 工具概览

原创 ImportNew ImportNew

（给ImportNew加星标，提高Java技能）

编译：ImportNew/覃佑桦
www.javacodegeeks.com/2019/12/openjdk-11-tools-of-the-trade.html

在Security Manager演讲中，我演示了如何使用Attach API。使用时需要知道准备附加的JVM PID。因为我的好友Evgeny Mandrikov没能参加上次的会议，所以单独为他做了一次演示。

要获取目标JVM的PID，我使用了ps -ef | grep java命令。Evgeny向我介绍了很多jps命令的知识，我发现除了常见JDK命令外，还有很多JDK命令不了解。下面列表中的命令可以帮助修复已部署应用中的问题。

jps：列出正在运行的JVM

使用jps命令行工具可以显示正在运行的JVM列表，根据需要决定输出信息的详细程度。

jps命令可以列出目标系统上instrumented JVM。这是一个实验性命令，不提供支持。

为了获取目标JVM的PID，我用了 ps -ef | grep java 命令。Evgeny这时向我介绍了jps命令，我发现解除了最常见的JDK命令，还有很多我不知道的命令。下面列表中的命令可以帮助修复已部署应用中的问题。

注意：Java 6加入了jps。这充分说明了“实验性”的真正含义。

jps

列表默认仅显示PID和启动类的简单名（或已启动的JAR名）：

560   Jps
99714 spring-petclinic-2.0.0.BUILD-SNAPSHOT.jar
95689 CommandServer

使用选项可以展示更多数据：

开启上述选项后输出如下：

99714 target/spring-petclinic-2.0.0.BUILD-SNAPSHOT.jar
679   sun.tools.jps.Jps -lvm -Xms8m \
          -Dapplication.home=/Library/Java/JavaVirtualMachines/jdk1.8.0_181.jdk/Contents/Home
95689 org.asciidoctor.diagram.CommandServer -Djava.awt.headless=true

jinfo：输出JVM启动数据

要解决生产环境中的问题，还需要提供运行中JVM的其他信息。包括完整的JVM标志、参数和系统属性。

使用jinfo命令可以为指定Java进程生成Java配置信息。这是一个实验性命令，不提供支持。

jinfo 95689

下面是示例输出（为了提高可读性，对结果进行了提取和格式化）：

Java System Properties:
#Fri Dec 07 16:22:25 CET 2018
    gopherProxySet=false
    awt.toolkit=sun.lwawt.macosx.LWCToolkit
    java.specification.version=11
    sun.cpu.isalist=
    sun.jnu.encoding=UTF-8
    ...
    java.class.version=55.0
    socksNonProxyHosts=local|*.local|169.254/16|*.169.254/16
 
VM Flags:
    -XX:CICompilerCount=3
    -XX:ConcGCThreads=1
    -XX:G1ConcRefinementThreads=4
    -XX:G1HeapRegionSize=1048576
    -XX:GCDrainStackTargetSize=64
    -XX:InitialHeapSize=268435456
    -XX:MarkStackSize=4194304
    -XX:MaxHeapSize=4294967296
    -XX:MaxNewSize=2576351232
    -XX:MinHeapDeltaBytes=1048576
    -XX:NonNMethodCodeHeapSize=5830092
    -XX:NonProfiledCodeHeapSize=122914074
    -XX:ProfiledCodeHeapSize=122914074
    -XX:ReservedCodeCacheSize=251658240
    -XX:+SegmentedCodeCache
    -XX:+UseCompressedClassPointers
    -XX:+UseCompressedOops
    -XX:+UseFastUnorderedTimeStamps
    -XX:+UseG1GC
 
VM Arguments:
    jvm_args:
        -Djava.awt.headless=true
    java_command:
        org.asciidoctor.diagram.CommandServer
    java_class_path (initial):
        ~/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/asciidoctor-diagram-1.5.9/lib/server-1.3.13.jar:
        ~/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/asciidoctor-diagram-1.5.9/lib/ditaa-1.3.13.jar:
        ~/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/asciidoctor-diagram-1.5.9/lib/ditaamini-0.11.jar:
        ~/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/asciidoctor-diagram-1.5.9/lib/plantuml-1.3.13.jar:
        ~/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/asciidoctor-diagram-1.5.9/lib/plantuml.jar:
        ~/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/asciidoctor-diagram-1.5.9/lib/jlatexmath-minimal-1.0.5.jar:
        ~/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/asciidoctor-diagram-1.5.9/lib/batik-all-1.7.jar
Launcher Type: SUN_STANDARD

下面这些选项可以控制输出内容：

jmap：输出JVM上与类相关的数据

接下来，有必要深入了解JVM上与类相关的数据：class loader统计数据、等待finalize的对象和对象堆。

可以使用jmap命令输出进程的详细信息。这是一个实验性命令，不提供支持。。

使用不同的选项会得到对应输出。输出class loader统计信息

jmap -clstats 95689

Index Super InstBytes KlassBytes annotations   CpAll MethodCount Bytecodes MethodAll   ROAll    RWAll    Total ClassName
    1    -1   1686600        504           0       0           0         0         0      24      616      640 [B
    2    -1    485288        504           0       0           0         0         0      24      616      640 [I
    3    20    420984        616         128   14224         109      4577     64472   18640    62104    80744 java.lang.String
    4    -1    375216        504           0       0           0         0         0      24      616      640 [C
    5    20    374448        672           0   22120         139      5682     46936   24616    47008    71624 java.lang.Class
    6    -1    238888        504           0       0           0         0         0      24      616      640 [Ljava.lang.Object;
    7    20    165440        584           0    1392           7       149      1864    1152     3008     4160 java.util.HashMap$Node
    8    20    141856        592           0    1368           9       213      2776    1488     3584     5072 java.util.concurrent.ConcurrentHashMap$Node
    9    20     71120        584           0    1400           7       171      2264    1208     3384     4592 java.util.TreeMap$Entry
...
 3085  3084         0        632           0     808           5        71       960     640     1920     2560 sun.util.resources.TimeZoneNamesBundle
 3086    20         0        600           0    1256           5       159      1000     856     2264     3120 sun.util.resources.provider.NonBaseLocaleDataMetaInfo
              5147912    1947360       10656 6473512       31831   1647775   9869272 6170712 13100408 19271120 Total
                26.7%      10.1%        0.1%   33.6%           -      8.6%     51.2%   32.0%    68.0%   100.0%
Index Super InstBytes KlassBytes annotations   CpAll MethodCount Bytecodes MethodAll   ROAll    RWAll    Total ClassName

输出Java对象堆的直方图

jmap -histo 95689

num     #instances         #bytes  class name (module)
-------------------------------------------------------
   1:       2578716      182530328  [I (java.base@11.0.1)
   2:        261988       71251184  [Z (java.base@11.0.1)
   3:        798811       57514392  java.util.regex.Matcher (java.base@11.0.1)
   4:        413769       28433240  [B (java.base@11.0.1)
   5:        296086       26055568  java.util.regex.Pattern (java.base@11.0.1)
   6:        301073       16858024  [Ljava.lang.Object; (java.base@11.0.1)
   7:        276719       15496264  [Ljava.util.regex.Pattern$GroupHead; (java.base@11.0.1)
   8:        798811       13032760  [Ljava.util.regex.IntHashSet; (java.base@11.0.1)
   9:        318781        7650744  java.util.regex.Pattern$BmpCharProperty (java.base@11.0.1)
  10:        289648        6951552  java.util.ArrayList (java.base@11.0.1)
...
1616:             1             16  sun.util.logging.PlatformLogger (java.base@11.0.1)
1617:             1             16  sun.util.resources.LocaleData$LocaleDataStrategy (java.base@11.0.1)
1618:             1             16  sun.util.resources.cldr.provider.CLDRLocaleDataMetaInfo (jdk.localedata@11.0.1)
Total      10605127      526098920

jstack：输出JVM线程信息

如果发生与线程相关的问题（例如死锁或活锁），线程详细信息会派上用场。

使用jstack命令可以打印指定Java进程中的线程堆栈跟踪信息。这是一个实验性命令，不提供支持。

jstack 95689

2018-12-07 19:06:01
Full thread dump OpenJDK 64-Bit Server VM (11.0.1+13 mixed mode):
 
Threads class SMR info:
_java_thread_list=0x00007fd1212fb270, length=13, elements={
0x00007fd120015800, 0x00007fd120051000, 0x00007fd120053800, 0x00007fd11e89c000,
0x00007fd120045800, 0x00007fd11f00f800, 0x00007fd12004a800, 0x00007fd11e8d9800,
0x00007fd120065000, 0x00007fd11f883000, 0x00007fd11f075800, 0x00007fd11ed4b000,
0x00007fd11f30e800
}
 
"main" #1 prio=5 os_prio=31 cpu=314567.92ms elapsed=2035.03s tid=0x00007fd120015800 nid=0x2403 runnable  [0x000070000bbac000]
   java.lang.Thread.State: RUNNABLE
    at java.net.SocketInputStream.socketRead0(java.base@11.0.1/Native Method)
    at java.net.SocketInputStream.socketRead(java.base@11.0.1/SocketInputStream.java:115)
    at java.net.SocketInputStream.read(java.base@11.0.1/SocketInputStream.java:168)
    at java.net.SocketInputStream.read(java.base@11.0.1/SocketInputStream.java:140)
    at java.io.BufferedInputStream.fill(java.base@11.0.1/BufferedInputStream.java:252)
    at java.io.BufferedInputStream.read(java.base@11.0.1/BufferedInputStream.java:271)
    - locked <0x00000007000d0558> (a java.io.BufferedInputStream)
    at org.asciidoctor.diagram.HTTPInputStream.readLine(HTTPInputStream.java:20)
    at org.asciidoctor.diagram.HTTPInputStream.readRequest(HTTPInputStream.java:56)
    at org.asciidoctor.diagram.CommandServer.processRequests(CommandServer.java:61)
    at org.asciidoctor.diagram.CommandServer.main(CommandServer.java:25)
 
...
 
"process reaper" #109 daemon prio=10 os_prio=31 cpu=538.50ms elapsed=1683.17s tid=0x00007fd11f30e800 nid=0x6507 waiting on condition  [0x000070000ba4e000]
   java.lang.Thread.State: TIMED_WAITING (parking)
    at jdk.internal.misc.Unsafe.park(java.base@11.0.1/Native Method)
    - parking to wait for  <0x000000070016fe20> (a java.util.concurrent.SynchronousQueue$TransferStack)
    at java.util.concurrent.locks.LockSupport.parkNanos(java.base@11.0.1/LockSupport.java:234)
    at java.util.concurrent.SynchronousQueue$TransferStack.awaitFulfill(java.base@11.0.1/SynchronousQueue.java:462)
    at java.util.concurrent.SynchronousQueue$TransferStack.transfer(java.base@11.0.1/SynchronousQueue.java:361)
    at java.util.concurrent.SynchronousQueue.poll(java.base@11.0.1/SynchronousQueue.java:937)
    at java.util.concurrent.ThreadPoolExecutor.getTask(java.base@11.0.1/ThreadPoolExecutor.java:1053)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(java.base@11.0.1/ThreadPoolExecutor.java:1114)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(java.base@11.0.1/ThreadPoolExecutor.java:628)
    at java.lang.Thread.run(java.base@11.0.1/Thread.java:834)
 
"VM Thread" os_prio=31 cpu=1139.30ms elapsed=2035.01s tid=0x00007fd11f88e000 nid=0x4b03 runnable
 
"GC Thread#0" os_prio=31 cpu=1888.39ms elapsed=2035.03s tid=0x00007fd11e805000 nid=0x5203 runnable
 
"GC Thread#1" os_prio=31 cpu=1951.89ms elapsed=2034.53s tid=0x00007fd11e8e1800 nid=0x9903 runnable
 
"GC Thread#2" os_prio=31 cpu=1897.20ms elapsed=2034.53s tid=0x00007fd11e8e2800 nid=0x5f03 runnable
 
"GC Thread#3" os_prio=31 cpu=1901.78ms elapsed=2034.53s tid=0x00007fd11e90d000 nid=0x6103 runnable
 
"G1 Main Marker" os_prio=31 cpu=0.57ms elapsed=2035.03s tid=0x00007fd11e84a000 nid=0x5003 runnable
 
"G1 Conc#0" os_prio=31 cpu=36.31ms elapsed=2035.03s tid=0x00007fd11e84a800 nid=0x3003 runnable
 
"G1 Refine#0" os_prio=31 cpu=8.48ms elapsed=2035.03s tid=0x00007fd11f882000 nid=0x3203 runnable
 
"G1 Refine#1" os_prio=31 cpu=2.95ms elapsed=2034.52s tid=0x00007fd11e9b1000 nid=0x9703 runnable
 
"G1 Refine#2" os_prio=31 cpu=0.06ms elapsed=2034.36s tid=0x00007fd11f939800 nid=0x6303 runnable
 
"G1 Young RemSet Sampling" os_prio=31 cpu=898.32ms elapsed=2035.03s tid=0x00007fd11e858800 nid=0x3303 runnable
"VM Periodic Task Thread" os_prio=31 cpu=933.68ms elapsed=2034.94s tid=0x00007fd11f00c800 nid=0xa603 waiting on condition
 
JNI global refs: 98, weak refs: 5

需要检查锁信息，可以使用-l选项。输出内容如下：

...
"main" #1 prio=5 os_prio=31 cpu=489307.36ms elapsed=3019.58s tid=0x00007fd120015800 nid=0x2403 runnable  [0x000070000bbac000]
   java.lang.Thread.State: RUNNABLE
    at java.net.SocketInputStream.socketRead0(java.base@11.0.1/Native Method)
    at java.net.SocketInputStream.socketRead(java.base@11.0.1/SocketInputStream.java:115)
    at java.net.SocketInputStream.read(java.base@11.0.1/SocketInputStream.java:168)
    at java.net.SocketInputStream.read(java.base@11.0.1/SocketInputStream.java:140)
    at java.io.BufferedInputStream.fill(java.base@11.0.1/BufferedInputStream.java:252)
    at java.io.BufferedInputStream.read(java.base@11.0.1/BufferedInputStream.java:271)
    - locked <0x00000007000d0558> (a java.io.BufferedInputStream)
    at org.asciidoctor.diagram.HTTPInputStream.readLine(HTTPInputStream.java:20)
    at org.asciidoctor.diagram.HTTPInputStream.readRequest(HTTPInputStream.java:56)
    at org.asciidoctor.diagram.CommandServer.processRequests(CommandServer.java:61)
    at org.asciidoctor.diagram.CommandServer.main(CommandServer.java:25)
 
   Locked ownable synchronizers:
    - None
 
"Reference Handler" #2 daemon prio=10 os_prio=31 cpu=0.94ms elapsed=3019.55s tid=0x00007fd120051000 nid=0x3603 waiting on condition  [0x000070000c2c1000]
   java.lang.Thread.State: RUNNABLE
    at java.lang.ref.Reference.waitForReferencePendingList(java.base@11.0.1/Native Method)
    at java.lang.ref.Reference.processPendingReferences(java.base@11.0.1/Reference.java:241)
    at java.lang.ref.Reference$ReferenceHandler.run(java.base@11.0.1/Reference.java:213)
 
   Locked ownable synchronizers:
    - None
...