Java虚拟机插曲之参数详解

蔚落 2022-06-11 08:36 141阅读 0赞

## JVM 参数选项 ##

jvm 可配置的参数选项可以参考 Oracle 官方网站给出的相关信息：[http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html][http_www.oracle.com_technetwork_java_javase_tech_vmoptions-jsp-140102.html]  
下面只列举其中的几个常用和容易掌握的配置选项：

<table style="margin:0px; padding:0px; border-collapse:collapse; border-spacing:0px; border:1px solid silver; word-break:break-word; color:rgb(0,0,0); font-family:Verdana,Arial,Helvetica,sans-serif; font-size:12px"> 
 <tbody style="margin:0px; padding:0px"> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;-Xms</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;初始堆大小。如：-Xms256m</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;-Xmx</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;最大堆大小。如：-Xmx512m</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;-Xmn</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;新生代大小。通常为 Xmx 的 1/3 或 1/4。新生代 = Eden + 2 个 Survivor 空间。实际可用空间为 = Eden + 1 个 Survivor，即 90% &nbsp;</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;-Xss</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;JDK1.5+ 每个线程堆栈大小为 1M，一般来说如果栈不是很深的话， 1M 是绝对够用了的。</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;-XX:NewRatio</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;新生代与老年代的比例，如 –XX:NewRatio=2，则新生代占整个堆空间的1/3，老年代占2/3</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;-XX:SurvivorRatio</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;新生代中 Eden 与 Survivor 的比值。默认值为 8。即 Eden 占新生代空间的 8/10，另外两个 Survivor 各占 1/10 &nbsp;</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;-XX:PermSize</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;永久代(方法区)的初始大小</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;-XX:MaxPermSize</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;永久代(方法区)的最大值</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;-XX:+PrintGCDetails</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;打印 GC 信息</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;-XX:+HeapDumpOnOutOfMemoryError</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> &nbsp;让虚拟机在发生内存溢出时 Dump 出当前的内存堆转储快照，以便分析用</td> 
  </tr> 
 </tbody> 
</table>

[http_www.oracle.com_technetwork_java_javase_tech_vmoptions-jsp-140102.html]: http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html