java虚拟机参数

1. 一行命令获取当前JVM所有可设置的参数以及当前默认值

   [root@localhost ~]$ java -XX:+PrintFlagsInitial  >>1.txt
   

   然后查看这个1.txt即可

   uintx AdaptivePermSizeWeight                    = 20              {product}             
   uintx AdaptiveSizeDecrementScaleFactor          = 4               {product}             
   uintx AdaptiveSizeMajorGCDecayTimeScale         = 10              {product}             
   uintx AdaptiveSizePausePolicy                   = 0               {product}             
   uintx AdaptiveSizePolicyCollectionCostMargin    = 50              {product}    
   

   具体的参数含义可以百度

2. 这条指令是默认执行在Path 环境 配置的jvm。

   [root@localhost ~]$ java -XX:+PrintCommandLineFlags -version
   -XX:InitialHeapSize=268435456 -XX:MaxHeapSize=4294967296 -XX:+PrintCommandLineFlags -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseParallelGC
   java version "1.8.0_141"
   Java(TM) SE Runtime Environment (build 1.8.0_141-b15)
   Java HotSpot(TM) 64-Bit Server VM (build 25.141-b15, mixed mode)