JMap工具使用

官方地址

• 使用方式

  jmap [options] pid
  

  • -clstats pid

    连接到正在运行的进程并打印Java堆的类装入器统计信息。如下图

    
    clstats示例.png

  • -finalizerinfo pid
    连接到正在运行的进程并打印关于等待结束的对象的信息。如下图
    

    finalizerinfo示例.png

  • -histo[:live] pid
    连接到正在运行的进程并打印Java对象堆的直方图。如果指定了live子选项，那么它只计数活动对象。
    

    histo示例.png

• -dump:<dump options> pid
  以hprof二进制格式，转储Java堆。<dump options>选项如下

  • live — When specified, dumps only the live objects; if not specified, then dumps all objects in the heap.
  • format=b — Dumps the Java heap,. in hprof binary format

  • file=filename — Dumps the heap to filename

    
    dump示例.png

• -heap pid
  打印java堆信息。如下

Parallel GC with 8 thread(s)        //jvm采用什么垃圾回收器

Heap Configuration:
   MinHeapFreeRatio         = 0     //jvm堆内存最小空闲比例,-XX:MinHeapFreeRatio=40低于这个值将扩展
   MaxHeapFreeRatio         = 100   //jvm堆内存最大空闲比例,-XX:MaxHeapFreeRatio=70超过这个值将收缩
   MaxHeapSize              = 2111832064 (2014.0MB) //jvm堆最大值
   NewSize                  = 44040192 (42.0MB) //jvm新生代默认值
   MaxNewSize               = 703594496 (671.0MB)//jvm新生代最大值
   OldSize                  = 88080384 (84.0MB)//jvm老年代默认值
   NewRatio                 = 2 //新生代和老年代比例 1:2
   SurvivorRatio            = 8 //survivor和eden比例 1:8
   MetaspaceSize            = 21807104 (20.796875MB) //元空间默认值
   CompressedClassSpaceSize = 1073741824 (1024.0MB) //
   MaxMetaspaceSize         = 17592186044415 MB //元空间最大值
   G1HeapRegionSize         = 0 (0.0MB) //

Heap Usage:
PS Young Generation
Eden Space:
   capacity = 147324928 (140.5MB)
   used     = 1841560 (1.7562484741210938MB)
   free     = 145483368 (138.7437515258789MB)
   1.2499989139651912% used
From Space:
   capacity = 11010048 (10.5MB)
   used     = 0 (0.0MB)
   free     = 11010048 (10.5MB)
   0.0% used
To Space:
   capacity = 12058624 (11.5MB)
   used     = 0 (0.0MB)
   free     = 12058624 (11.5MB)
   0.0% used
PS Old Generation
   capacity = 95944704 (91.5MB)
   used     = 11275232 (10.752899169921875MB)
   free     = 84669472 (80.74710083007812MB)
   11.751802371499316% used

16005 interned Strings occupying 1509768 bytes.