This closes #1324

artemis-server/src/main/java/org/apache/activemq/artemis/core/paging/impl/Page.java

@@ -16,18 +16,26 @@
  */
 package org.apache.activemq.artemis.core.paging.impl;
 
+import java.io.File;
+import java.io.IOException;
+import java.io.RandomAccessFile;
 import java.nio.ByteBuffer;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicInteger;
 
+import io.netty.util.internal.PlatformDependent;
 import org.apache.activemq.artemis.api.core.ActiveMQBuffer;
 import org.apache.activemq.artemis.api.core.ActiveMQBuffers;
 import org.apache.activemq.artemis.api.core.ICoreMessage;
 import org.apache.activemq.artemis.api.core.SimpleString;
 import org.apache.activemq.artemis.core.io.SequentialFile;
 import org.apache.activemq.artemis.core.io.SequentialFileFactory;
+import org.apache.activemq.artemis.core.io.mapped.MappedSequentialFileFactory;
+import org.apache.activemq.artemis.core.io.nio.NIOSequentialFileFactory;
 import org.apache.activemq.artemis.core.paging.PagedMessage;
 import org.apache.activemq.artemis.core.paging.cursor.LivePageCache;
 import org.apache.activemq.artemis.core.paging.cursor.PageSubscriptionCounter;
@@ -78,6 +86,8 @@ public final class Page implements Comparable<Page> {
     */
    private Set<PageSubscriptionCounter> pendingCounters;
 
+   private boolean canBeMapped;
+
    public Page(final SimpleString storeName,
                final StorageManager storageManager,
                final SequentialFileFactory factory,
@@ -88,6 +98,7 @@ public final class Page implements Comparable<Page> {
       fileFactory = factory;
       this.storageManager = storageManager;
       this.storeName = storeName;
+      this.canBeMapped = fileFactory instanceof NIOSequentialFileFactory || fileFactory instanceof MappedSequentialFileFactory;
    }
 
    public int getPageId() {
@@ -107,9 +118,22 @@ public final class Page implements Comparable<Page> {
          throw ActiveMQMessageBundle.BUNDLE.invalidPageIO();
       }
 
-      ArrayList<PagedMessage> messages = new ArrayList<>();
+      final List<PagedMessage> messages = new ArrayList<>();
 
-      size.set((int) file.size());
+      size.lazySet((int) file.size());
+
+      if (this.canBeMapped) {
+         readFromMapped(storage, messages);
+      } else {
+         readFromSequentialFile(storage, messages);
+      }
+
+      numberOfMessages.lazySet(messages.size());
+
+      return messages;
+   }
+
+   private void readFromSequentialFile(StorageManager storage, List<PagedMessage> messages) throws Exception {
       // Using direct buffer, as described on https://jira.jboss.org/browse/HORNETQ-467
       ByteBuffer directBuffer = storage.allocateDirectBuffer((int) file.size());
       ActiveMQBuffer fileBuffer = null;
@@ -122,51 +146,76 @@ public final class Page implements Comparable<Page> {
 
          fileBuffer = ActiveMQBuffers.wrappedBuffer(directBuffer);
          fileBuffer.writerIndex(fileBuffer.capacity());
-
+         read(storage, fileBuffer, messages);
-         while (fileBuffer.readable()) {
-            final int position = fileBuffer.readerIndex();
-
-            byte byteRead = fileBuffer.readByte();
-
-            if (byteRead == Page.START_BYTE) {
-               if (fileBuffer.readerIndex() + DataConstants.SIZE_INT < fileBuffer.capacity()) {
-                  int messageSize = fileBuffer.readInt();
-                  int oldPos = fileBuffer.readerIndex();
-                  if (fileBuffer.readerIndex() + messageSize < fileBuffer.capacity() && fileBuffer.getByte(oldPos + messageSize) == Page.END_BYTE) {
-                     PagedMessage msg = new PagedMessageImpl(storageManager);
-                     msg.decode(fileBuffer);
-                     byte b = fileBuffer.readByte();
-                     if (b != Page.END_BYTE) {
-                        // Sanity Check: This would only happen if there is a bug on decode or any internal code, as
-                        // this
-                        // constraint was already checked
-                        throw new IllegalStateException("Internal error, it wasn't possible to locate END_BYTE " + b);
-                     }
-                     msg.initMessage(storage);
-                     if (logger.isTraceEnabled()) {
-                        logger.trace("Reading message " + msg + " on pageId=" + this.pageId + " for address=" + storeName);
-                     }
-                     messages.add(msg);
-                  } else {
-                     markFileAsSuspect(file.getFileName(), position, messages.size());
-                     break;
-                  }
-               }
-            } else {
-               markFileAsSuspect(file.getFileName(), position, messages.size());
-               break;
-            }
-         }
       } finally {
          if (fileBuffer != null) {
             fileBuffer.byteBuf().unwrap().release();
          }
          storage.freeDirectBuffer(directBuffer);
       }
+   }
 
-      numberOfMessages.set(messages.size());
+   private static MappedByteBuffer mapFileForRead(File file, int fileSize) {
+      try (RandomAccessFile raf = new RandomAccessFile(file, "rw");
+           FileChannel channel = raf.getChannel()) {
+         return channel.map(FileChannel.MapMode.READ_ONLY, 0, fileSize);
+      } catch (Exception e) {
+         throw new IllegalStateException(e);
+      }
+   }
 
-      return messages;
+   private int readFromMapped(StorageManager storage, List<PagedMessage> messages) throws IOException {
+      file.position(0);
+      //use a readonly mapped view of the file
+      final MappedByteBuffer mappedByteBuffer = mapFileForRead(this.file.getJavaFile(), size.get());
+      try {
+         final ActiveMQBuffer fileBuffer = ActiveMQBuffers.wrappedBuffer(mappedByteBuffer);
+         fileBuffer.writerIndex(fileBuffer.capacity());
+         return read(storage, fileBuffer, messages);
+      } finally {
+         //unmap the file after read it to avoid GC to take care of it
+         PlatformDependent.freeDirectBuffer(mappedByteBuffer);
+      }
+   }
+
+   private int read(StorageManager storage, ActiveMQBuffer fileBuffer, List<PagedMessage> messages) {
+      int readMessages = 0;
+      while (fileBuffer.readable()) {
+         final int position = fileBuffer.readerIndex();
+
+         byte byteRead = fileBuffer.readByte();
+
+         if (byteRead == Page.START_BYTE) {
+            if (fileBuffer.readerIndex() + DataConstants.SIZE_INT < fileBuffer.capacity()) {
+               int messageSize = fileBuffer.readInt();
+               int oldPos = fileBuffer.readerIndex();
+               if (fileBuffer.readerIndex() + messageSize < fileBuffer.capacity() && fileBuffer.getByte(oldPos + messageSize) == Page.END_BYTE) {
+                  PagedMessage msg = new PagedMessageImpl(storageManager);
+                  msg.decode(fileBuffer);
+                  byte b = fileBuffer.readByte();
+                  if (b != Page.END_BYTE) {
+                     // Sanity Check: This would only happen if there is a bug on decode or any internal code, as
+                     // this
+                     // constraint was already checked
+                     throw new IllegalStateException("Internal error, it wasn't possible to locate END_BYTE " + b);
+                  }
+                  msg.initMessage(storage);
+                  if (logger.isTraceEnabled()) {
+                     logger.trace("Reading message " + msg + " on pageId=" + this.pageId + " for address=" + storeName);
+                  }
+                  readMessages++;
+                  messages.add(msg);
+               } else {
+                  markFileAsSuspect(file.getFileName(), position, messages.size());
+                  break;
+               }
+            }
+         } else {
+            markFileAsSuspect(file.getFileName(), position, messages.size());
+            break;
+         }
+      }
+      return readMessages;
    }
 
    public synchronized void write(final PagedMessage message) throws Exception {