查看不同JDK版本的默认垃圾回收器

爱被打了一巴掌 2022-09-01 14:54 117阅读 0赞

# 一 点睛 #

\-XX:+PrintcommandLineFlags：查看命令行相关参数（包含使用的垃圾收集器）

使用命令行指令：jinfo -flag  相关垃圾回收器参数  进程ID

# 二 代码 #

/**
    * -XX:+PrintCommandLineFlags
    */
    public class GCUseTest {
        public static void main(String[] args) {
            ArrayList<byte[]> list = new ArrayList<>();
    
    
            while (true) {
                byte[] arr = new byte[100];
                list.add(arr);
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

# 三 JDK 8 #

## 1 运行结果 ##

> \-XX:InitialHeapSize=250603712 -XX:MaxHeapSize=4009659392 -XX:+PrintCommandLineFlags -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:-UseLargePagesIndividualAllocation -XX:+UseParallelGC

## 2 控制台测试 ##

> E:\\JVMDemo>jps
> 
> 2384
> 
> 15636 GCUseTest
> 
> 9604 Launcher
> 
> 12120 RemoteMavenServer36
> 
> 15608 Jps
> 
> E:\\JVMDemo>jinfo -flag UseParallelGC 15636
> 
> \-XX:+UseParallelGC
> 
> E:\\JVMDemo>jinfo -flag UseParallelOldGC 15636
> 
> \-XX:+UseParallelOldGC

# 四 JDK 9 #

## 1 运行结果 ##

> D:\\ProgramFiles\\Java\\jdk-9\\bin\\java.exe -XX:+PrintCommandLineFlags -javaagent:D:\\ProgramFiles\\JetBrains\\IDEA\\lib\\idea\_rt.jar=50715:D:\\ProgramFiles\\JetBrains\\IDEA\\bin -Dfile.encoding=UTF-8 -classpath E:\\JVMDemo\\out\\production\\chapter17 com.atguigu.java.GCUseTest
> 
> \-XX:G1ConcRefinementThreads=8 -XX:InitialHeapSize=250603712 -XX:MaxHeapSize=4009659392 -XX:+PrintCommandLineFlags -XX:ReservedCodeCacheSize=251658240 -XX:+SegmentedCodeCache -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseG1GC -XX:-UseLargePagesIndividualAllocation

## 2 控制台测试 ##

> E:\\JVMDemo>jps
> 
> 2384
> 
> 5044 Jps
> 
> 12120 RemoteMavenServer36
> 
> 3564 GCUseTest
> 
> 4668 Launcher
> 
> E:\\JVMDemo>jinfo -flag UseG1GC 3564
> 
> \-XX:+UseG1GC
> 
> E:\\JVMDemo>jinfo -flag UseParallelGC 3564
> 
> \-XX:-UseParallelGC
> 
> E:\\JVMDemo>jinfo -flag UseParallelOldGC 3564
> 
> \-XX:-UseParallelOldGC