svn commit: r1539909 - /hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/nativeio/NativeIO.java

[cmccabe]

Author: cmccabe
Date: Fri Nov  8 03:00:19 2013
New Revision: 1539909

URL: http://svn.apache.org/r1539909
Log:
HDFS-5394: Fix race conditions in DN caching and uncaching (cmccabe)

Modified:
    
hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/nativeio/NativeIO.java

Modified: 
hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/nativeio/NativeIO.java
URL: 
http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/nativeio/NativeIO.java?rev=1539909&r1=1539908&r2=1539909&view=diff
==============================================================================
--- 
hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/nativeio/NativeIO.java
 (original)
+++ 
hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/nativeio/NativeIO.java
 Fri Nov  8 03:00:19 2013
@@ -23,7 +23,9 @@ import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.RandomAccessFile;
+import java.lang.reflect.Field;
 import java.nio.ByteBuffer;
+import java.nio.MappedByteBuffer;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
@@ -34,10 +36,11 @@ import org.apache.hadoop.fs.CommonConfig
 import org.apache.hadoop.io.SecureIOUtils.AlreadyExistsException;
 import org.apache.hadoop.util.NativeCodeLoader;
 import org.apache.hadoop.util.Shell;
-
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import sun.misc.Unsafe;
+
 import com.google.common.annotations.VisibleForTesting;
 
 /**
@@ -271,6 +274,26 @@ public class NativeIO {
       }
       munlock_native(buffer, len);
     }
+    
+    /**
+     * Unmaps the block from memory. See munmap(2).
+     *
+     * There isn't any portable way to unmap a memory region in Java.
+     * So we use the sun.nio method here.
+     * Note that unmapping a memory region could cause crashes if code
+     * continues to reference the unmapped code.  However, if we don't
+     * manually unmap the memory, we are dependent on the finalizer to
+     * do it, and we have no idea when the finalizer will run.
+     *
+     * @param buffer    The buffer to unmap.
+     */
+    public static void munmap(MappedByteBuffer buffer) {
+      if (buffer instanceof sun.nio.ch.DirectBuffer) {
+        sun.misc.Cleaner cleaner =
+            ((sun.nio.ch.DirectBuffer)buffer).cleaner();
+        cleaner.clean();
+      }
+    }
 
     /** Linux only methods used for getOwner() implementation */
     private static native long getUIDforFDOwnerforOwner(FileDescriptor fd) 
throws IOException;
@@ -539,6 +562,21 @@ public class NativeIO {
 
   private static native long getMemlockLimit0();
   
+  /**
+   * @return the operating system's page size.
+   */
+  public static long getOperatingSystemPageSize() {
+    try {
+      Field f = Unsafe.class.getDeclaredField("theUnsafe");
+      f.setAccessible(true);
+      Unsafe unsafe = (Unsafe)f.get(null);
+      return unsafe.pageSize();
+    } catch (Throwable e) {
+      LOG.warn("Unable to get operating system page size.  Guessing 4096.", e);
+      return 4096;
+    }
+  }
+
   private static class CachedUid {
     final long timestamp;
     final String username;