【JVM】【linux】linux上执行jmap命令查看JVM内存使用情况，报错：sun.jvm.hotspot.debugger.NoSuchSymbolException: Could not find symbol "gHotSpotVMTypes" in any of the known library name

运行命令：

jmap -heap

报错如下：

Attaching to process ID , please wait...
sun.jvm.hotspot.debugger.NoSuchSymbolException: Could not find symbol "gHotSpotVMTypes" in any of the known library names (libjvm.so, libjvm_g.so, gamma_g)
    at sun.jvm.hotspot.HotSpotTypeDataBase.lookupInProcess(HotSpotTypeDataBase.java:)
    at sun.jvm.hotspot.HotSpotTypeDataBase.readVMTypes(HotSpotTypeDataBase.java:)
    at sun.jvm.hotspot.HotSpotTypeDataBase.<init>(HotSpotTypeDataBase.java:)
    at sun.jvm.hotspot.bugspot.BugSpotAgent.setupVM(BugSpotAgent.java:)
    at sun.jvm.hotspot.bugspot.BugSpotAgent.go(BugSpotAgent.java:)
    at sun.jvm.hotspot.bugspot.BugSpotAgent.attach(BugSpotAgent.java:)
    at sun.jvm.hotspot.tools.Tool.start(Tool.java:)
    at sun.jvm.hotspot.tools.HeapSummary.main(HeapSummary.java:)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:)
    at java.lang.reflect.Method.invoke(Method.java:)
    at sun.tools.jmap.JMap.runTool(JMap.java:)
    at sun.tools.jmap.JMap.main(JMap.java:)
Debugger attached successfully.
sun.jvm.hotspot.tools.HeapSummary requires a java VM process/core!

报错原因：

　　根据错误提示，可以看出来，需要一个java jvm的核心进程。

　　明明PID就是我java进程的PID，进程编号呀。

错误原因：

　　PID不是你要查看的JAVA进程的PID，注意区分你到底要查看那个JVM进程。

解决方法：

　　查看java进程的PID

ps -ef | grep java

　　现在自己查看一下，就可以发现

　　6709是另一个位置的java进程。

　　19570才是我们当前想要查看的JVM进程。

　　因为自己安装的java路径在/mnt/apps/soft/java路径。配置的环境变量也是这个路径下的JDK.

　　所以运行jmap指定错误的PID就导致了开始的错误。

　　现在修改jmap指定的PID

jmap -heap

运行成功：

Attaching to process ID , please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.80-b11using thread-local object allocation.
Parallel GC with  thread(s)Heap Configuration:
   MinHeapFreeRatio =
   MaxHeapFreeRatio =
   MaxHeapSize      =  (.0MB)
   NewSize          =  (.25MB)
   MaxNewSize       =  MB
   OldSize          =  (.1875MB)
   NewRatio         =
   SurvivorRatio    =
   PermSize         =  (.75MB)
   MaxPermSize      =  (.0MB)
   G1HeapRegionSize =  (.0MB)Heap Usage:
PS Young Generation
Eden Space:
   capacity =  (.0MB)
   used     =  (.844123840332MB)
   free     =  (.155876159668MB)
   44.17879830305825% used
From Space:
   capacity =  (.5MB)
   used     =  (.4843902587890625MB)
   free     =  (.01560974121094MB)
   0.7395271126550572% used
To Space:
   capacity =  (.0MB)
   used     =  (.0MB)
   free     =  (.0MB)
   0.0% used
PS Old Generation
   capacity =  (.0MB)
   used     =  (.53690338134766MB)
   free     =  (.46309661865234MB)
   53.88256201997471% used
PS Perm Generation
   capacity =  (.0MB)
   used     =  (.81534576416016MB)
   free     =  (.184654235839844MB)
   87.57968995629287% used interned Strings occupying  bytes.