如何使用 jdk 11 读取堆状态

Question

使用 jdk 8 时，这些是我计算进程运行时消耗多少内存的步骤：

/usr/java/latest/bin>: ./jps
  27116 Main
  7591 Jps
  2879 AmbusProcessor   

然后选取进程 ID 来检查堆的状态：

/usr/java/latest/bin>: ./jmap -heap 2879  

Attaching to process ID 2879, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.45-b08
using thread-local object allocation.
Parallel GC with 13 thread(s)
Heap Configuration:
   MinHeapFreeRatio = 40
   MaxHeapFreeRatio = 70
   MaxHeapSize      = 68719476736 (65536.0MB)     
   NewSize          = 1310720 (1.25MB)
   MaxNewSize       = 17592186044415 MB
   OldSize          = 5439488 (5.1875MB)
   NewRatio         = 2
   SurvivorRatio    = 8
   PermSize         = 21757952 (20.75MB)
   MaxPermSize      = 134217728 (128.0MB)
   G1HeapRegionSize = 0 (0.0MB)
Heap Usage:
PS Young Generation
Eden Space:    
   capacity = 15427698688 (14713.0MB)
   used     = 9122094480 (8699.507217407227MB)
   free     = 6305604208 (6013.492782592773MB)
   59.128031111311266% used
From Space:
   capacity = 2062024704 (1966.5MB)
   used     = 813973552 (776.2656707763672MB)
   free     = 1248051152 (1190.2343292236328MB)
   39.474481097196396% used
To Space:   
   capacity = 1944059904 (1854.0MB)
   used     = 0 (0.0MB)
   free     = 1944059904 (1854.0MB)
   0.0% used
PS Old Generation  
   capacity = 8520204288 (8125.5MB)
   used     = 6649238896 (6341.208358764648MB)
   free     = 1870965392 (1784.2916412353516MB)
   78.04083882548333% used
PS Perm Generation
   capacity = 31981568 (30.5MB)
   used     = 16156728 (15.408256530761719MB)
   free     = 15824840 (15.091743469238281MB)
   50.518873871349896% used
6141 interned Strings occupying 609896 bytes.

我正在寻找一种读取状态的方法，该状态应类似于上述示例，但是，找不到像 openjdk 11 这样的选项。我已经在 openjdk11 上的 jmap 上尝试了所有可能的选项。还有没有办法使用 openjdk11 获得这种状态读取？我正在尝试在 outOfMemory 发生时准确转储

Answer 1

对于较新的 Java 版本(如 JDK 11(，您可以使用以下命令：

jhsdb jmap --heap --pid <pid>

输出与Java 8和jmap几乎相同。

Answer 2

有一些 JVM 选项可以通过记录 GC 信息来帮助您：

  -XX:+PrintGCDetails
  -XX:+PrintGCDateStamps
  -XX:+PrintHeapAtGC
  -XX:+PrintTenuringDistribution
  -XX:+PrintGCApplicationStoppedTime
  -XX:+HeapDumpOnOutOfMemoryError
  -XX:+UseGCLogFileRotation
  -XX:NumberOfGCLogFiles=10
  -XX:GCLogFileSize=10M

由 HeapDumpOnOutOfMemoryError 创建的文件可以使用 JDK 附带的工具进行分析。另请参阅 https://docs.oracle.com/javase/7/docs/webnotes/tsg/TSG-VM/html/clopts.html

编辑：还有一些关于在Java 11中调试内存问题的官方文档：https://docs.oracle.com/en/java/javase/11/troubleshoot/troubleshoot-memory-leaks.html