错误场景

今天使用jmap -heap命令查看堆的详细信息报错。

[root@instance-2gak1pfv debuginfo]# java -version
openjdk version "1.8.0_191"
OpenJDK Runtime Environment (build 1.8.0_191-b12)
OpenJDK 64-Bit Server VM (build 25.191-b12, mixed mode)

[root@instance-2gak1pfv debuginfo]# jps -l
110386 org.apache.zookeeper.server.quorum.QuorumPeerMain
40565 sun.tools.jps.Jps
[root@instance-2gak1pfv debuginfo]# jmap -heap 110386
Attaching to process ID 110386, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.191-b12

using thread-local object allocation.
Mark Sweep Compact GC

Heap Configuration:
   MinHeapFreeRatio         = 40
   MaxHeapFreeRatio         = 70
   MaxHeapSize              = 255852544 (244.0MB)
   NewSize                  = 5570560 (5.3125MB)
   MaxNewSize               = 85262336 (81.3125MB)
   OldSize                  = 11206656 (10.6875MB)
   NewRatio                 = 2
   SurvivorRatio            = 8
   MetaspaceSize            = 21807104 (20.796875MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 17592186044415 MB
   G1HeapRegionSize         = 0 (0.0MB)

Heap Usage:
Exception in thread "main" java.lang.reflect.InvocationTargetException
    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 sun.tools.jmap.JMap.runTool(JMap.java:201)
    at sun.tools.jmap.JMap.main(JMap.java:130)
Caused by: java.lang.RuntimeException: unknown CollectedHeap type : class sun.jvm.hotspot.gc_interface.CollectedHeap
    at sun.jvm.hotspot.tools.HeapSummary.run(HeapSummary.java:157)
    at sun.jvm.hotspot.tools.Tool.startInternal(Tool.java:260)
    at sun.jvm.hotspot.tools.Tool.start(Tool.java:223)
    at sun.jvm.hotspot.tools.Tool.execute(Tool.java:118)
    at sun.jvm.hotspot.tools.HeapSummary.main(HeapSummary.java:50)
    ... 6 more

解决办法：
安装debuginfo，去网站http://debuginfo.centos.org/7/x86_64里面找匹配当前的openjdk的版本，小版本号也要匹配上。然后使用wget命令下载

wget http://debuginfo.centos.org/7/x86_64/java-1.8.0-openjdk-debuginfo-1.8.0.191.b12-1.el7_6.x86_64.rpm

使用rpm命令安装

rpm -ivh java-1.8.0-openjdk-debuginfo-1.8.0.191.b12-1.el7_6.x86_64.rpm

然后查看是否安装了debuginfo

[root@izuf6ea4rfo45y44oj74jhz logs]# rpm -qa|grep debuginfo
java-1.8.0-openjdk-debuginfo-1.8.0.191.b12-1.el7_6.x86_64

执行jmap -heap命令查看堆详细信息

[root@izuf6ea4rfo45y44oj74jhz logs]# jmap -heap 1421
Attaching to process ID 1421, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.191-b12

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 = 48758784 (46.5MB)
   used     = 42933176 (40.94426727294922MB)
   free     = 5825608 (5.555732727050781MB)
   88.05218768376176% used
Eden Space:
   capacity = 43384832 (41.375MB)
   used     = 42933176 (40.94426727294922MB)
   free     = 451656 (0.43073272705078125MB)
   98.95895413401624% used
From Space:
   capacity = 5373952 (5.125MB)
   used     = 0 (0.0MB)
   free     = 5373952 (5.125MB)
   0.0% used
To Space:
   capacity = 5373952 (5.125MB)
   used     = 0 (0.0MB)
   free     = 5373952 (5.125MB)
   0.0% used
tenured generation:
   capacity = 108146688 (103.13671875MB)
   used     = 64887344 (61.88139343261719MB)
   free     = 43259344 (41.25532531738281MB)
   59.99938158069159% used

21962 interned Strings occupying 2552376 bytes.