one~

chenzhuo@picooc.com · chenzhuo@picooc.com · commit 5a9c4e6c188c · 2018-12-15T14:41:18.000+08:00
diff --git a/src/main/java/com/sun/jvm/Jvm/AccessDirectBuffer.java b/src/main/java/com/sun/jvm/Jvm/AccessDirectBuffer.java
@@ -0,0 +1,50 @@
+package com.sun.jvm.Jvm;
+
+import java.nio.ByteBuffer;
+
+/**
+ * @ClassName AccessDirectBuffer
+ * @Despacito TODO
+ * @Author chenzhuo
+ * @Version 1.0
+ * 堆外内存的使用
+ * 堆外内存要比直接使用堆内存快
+ * 但是堆外内存要限制使用的量，要不就会oom
+ **/
+public class AccessDirectBuffer {
+    public void directAccess(){
+        long startTime = System.currentTimeMillis();
+        testWrite();
+        long endTime = System.currentTimeMillis();
+        System.out.println("testDirectWrite:" + (endTime - startTime));
+    }
+    public void bufferAccess(){
+        long startTime = System.currentTimeMillis();
+        testWrite();
+        long endTime = System.currentTimeMillis();
+        System.out.println("testBufferWrite:" + (endTime - startTime));
+    }
+
+    private void testWrite() {
+
+        ByteBuffer byteBudder = ByteBuffer.allocateDirect(500);
+        for (int i = 0; i < 100000; i++) {
+            for (int j = 0; j < 99; j++) {
+                byteBudder.putInt(j);
+            }
+            byteBudder.flip();
+            for (int j = 0; j < 99; j++) {
+                byteBudder.get();
+            }
+            byteBudder.clear();
+        }
+        long endTime = System.currentTimeMillis();
+
+    }
+
+    public static void main(String[] args) {
+        AccessDirectBuffer accessDirectBuffer = new AccessDirectBuffer();
+        accessDirectBuffer.bufferAccess();;
+        accessDirectBuffer.directAccess();
+    }
+}
diff --git a/src/main/java/com/sun/jvm/Jvm/DumpOOM.java b/src/main/java/com/sun/jvm/Jvm/DumpOOM.java
@@ -0,0 +1,19 @@
+package com.sun.jvm.Jvm;
+
+import java.util.Vector;
+
+/**
+ * @ClassName DumpOOM
+ * @Despacito TODO
+ * @Author chenzhuo
+ * @Version 1.0
+ **/
+public class DumpOOM {
+    public static void main(String[] args) {
+        Vector<byte[]> vector = new Vector<>();
+        for (int i =0;i<25;i++){
+            vector.add(new byte[1024*1024]);
+        }
+
+    }
+}
diff --git a/src/main/java/com/sun/jvm/Jvm/SimpleHeadpAlloc.java b/src/main/java/com/sun/jvm/Jvm/SimpleHeadpAlloc.java
@@ -8,14 +8,15 @@
  * -Xmx20m -Xms5m -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -XX:+UseSerialGC
  **/
 public class SimpleHeadpAlloc {
-    public static void main(String[] args) {
+    public static void main(String[] args) throws InterruptedException {
         getOut();
-        byte[] b = new byte[1*1024*1024];
+        byte[] b = new byte[1024 * 1024];
         System.out.println("分配了1m空间给数组");
         getOut();
         b = new byte[4*1024*1024];
         System.out.println("分配了4m空间给数组");
         getOut();
+        Thread.sleep(30000);
     }
 
     private static void getOut() {
