diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 35ecc77febb..3d8438cf6d3 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -285,6 +285,8 @@ Release 2.6.0 - UNRELEASED
     HDFS-7153. Add storagePolicy to NN edit log during file creation.
     (Arpit Agarwal)
 
+    HDFS-7158. Reduce the memory usage of WebImageViewer. (wheat9)
+
   OPTIMIZATIONS
 
     HDFS-6690. Deduplicate xattr names in memory. (wang)
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/FSImageHandler.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/FSImageHandler.java
index b6d760aab9b..dea64229205 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/FSImageHandler.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/FSImageHandler.java
@@ -24,6 +24,9 @@ import java.util.Map;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.hdfs.web.JsonUtil;
+import org.apache.hadoop.ipc.RemoteException;
+import org.jboss.netty.channel.ChannelFuture;
 import org.jboss.netty.channel.ChannelFutureListener;
 import org.jboss.netty.channel.ChannelHandlerContext;
 import org.jboss.netty.channel.MessageEvent;
@@ -37,99 +40,92 @@ import org.jboss.netty.handler.codec.http.HttpResponseStatus;
 import org.jboss.netty.handler.codec.http.HttpVersion;
 import org.jboss.netty.handler.codec.http.QueryStringDecoder;
 
+import javax.management.Query;
+
 /**
  * Implement the read-only WebHDFS API for fsimage.
  */
-public class FSImageHandler extends SimpleChannelUpstreamHandler {
+class FSImageHandler extends SimpleChannelUpstreamHandler {
   public static final Log LOG = LogFactory.getLog(FSImageHandler.class);
-  private final FSImageLoader loader;
+  private final FSImageLoader image;
 
-  public FSImageHandler(FSImageLoader loader) throws IOException {
-    this.loader = loader;
+  FSImageHandler(FSImageLoader image) throws IOException {
+    this.image = image;
   }
 
   @Override
   public void messageReceived(
       ChannelHandlerContext ctx, MessageEvent e) throws Exception {
-    String op = getOp(e);
+    ChannelFuture future = e.getFuture();
     try {
-      String path = getPath(e);
-      handleOperation(op, path, e);
-    } catch (Exception ex) {
-      notFoundResponse(e);
-      LOG.warn(ex.getMessage());
+      future = handleOperation(e);
     } finally {
-      e.getFuture().addListener(ChannelFutureListener.CLOSE);
+      future.addListener(ChannelFutureListener.CLOSE);
     }
   }
 
-  /** return the op parameter in upper case */
-  private String getOp(MessageEvent e) {
-    Map<String, List<String>> parameters = getDecoder(e).getParameters();
-    if (parameters.containsKey("op")) {
-      return parameters.get("op").get(0).toUpperCase();
-    } else {
-      // return "" to avoid NPE
-      return "";
-    }
-  }
-
-  private String getPath(MessageEvent e) throws FileNotFoundException {
-    String path = getDecoder(e).getPath();
-    // trim "/webhdfs/v1" to keep compatibility with WebHDFS API
-    if (path.startsWith("/webhdfs/v1/")) {
-      return path.replaceFirst("/webhdfs/v1", "");
-    } else {
-      throw new FileNotFoundException("Path: " + path + " should " +
-          "start with \"/webhdfs/v1/\"");
-    }
-  }
-
-  private QueryStringDecoder getDecoder(MessageEvent e) {
-    HttpRequest request = (HttpRequest) e.getMessage();
-    return new QueryStringDecoder(request.getUri());
-  }
-
-  private void handleOperation(String op, String path, MessageEvent e)
+  private ChannelFuture handleOperation(MessageEvent e)
       throws IOException {
     HttpRequest request = (HttpRequest) e.getMessage();
     HttpResponse response = new DefaultHttpResponse(
-        HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
-    response.setHeader(HttpHeaders.Names.CONTENT_TYPE,
-        "application/json");
-    String content = null;
+            HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
+    response.setHeader(HttpHeaders.Names.CONTENT_TYPE, "application/json");
 
-    if (request.getMethod() == HttpMethod.GET){
-      if (op.equals("GETFILESTATUS")) {
-        content = loader.getFileStatus(path);
-      } else if (op.equals("LISTSTATUS")) {
-        content = loader.listStatus(path);
-      } else if (op.equals("GETACLSTATUS")) {
-        content = loader.getAclStatus(path);
-      } else {
-        response.setStatus(HttpResponseStatus.BAD_REQUEST);
-      }
-    } else {
-      // only HTTP GET is allowed since fsimage is read-only.
+    if (request.getMethod() != HttpMethod.GET) {
       response.setStatus(HttpResponseStatus.METHOD_NOT_ALLOWED);
+      return e.getChannel().write(response);
     }
 
-    if (content != null) {
-      HttpHeaders.setContentLength(response, content.length());
+    QueryStringDecoder decoder = new QueryStringDecoder(request.getUri());
+    final String op = getOp(decoder);
+
+    String content;
+    String path = null;
+    try {
+      path = getPath(decoder);
+      if ("GETFILESTATUS".equals(op)) {
+        content = image.getFileStatus(path);
+      } else if ("LISTSTATUS".equals(op)) {
+        content = image.listStatus(path);
+      } else if ("GETACLSTATUS".equals(op)) {
+        content = image.getAclStatus(path);
+      } else {
+        throw new IllegalArgumentException("Invalid value for webhdfs parameter" + " \"op\"");
+      }
+    } catch (IllegalArgumentException ex) {
+      response.setStatus(HttpResponseStatus.BAD_REQUEST);
+      content = JsonUtil.toJsonString(ex);
+    } catch (FileNotFoundException ex) {
+      response.setStatus(HttpResponseStatus.NOT_FOUND);
+      content = JsonUtil.toJsonString(ex);
+    } catch (Exception ex) {
+      content = JsonUtil.toJsonString(ex);
     }
+
+    HttpHeaders.setContentLength(response, content.length());
     e.getChannel().write(response);
-
-    if (content != null) {
-      e.getChannel().write(content);
-    }
+    ChannelFuture future = e.getChannel().write(content);
 
     LOG.info(response.getStatus().getCode() + " method="
         + request.getMethod().getName() + " op=" + op + " target=" + path);
+
+    return future;
   }
 
-  private void notFoundResponse(MessageEvent e) {
-    HttpResponse response = new DefaultHttpResponse(
-        HttpVersion.HTTP_1_1, HttpResponseStatus.NOT_FOUND);
-    e.getChannel().write(response);
+  private static String getOp(QueryStringDecoder decoder) {
+    Map<String, List<String>> parameters = decoder.getParameters();
+    return parameters.containsKey("op")
+            ? parameters.get("op").get(0).toUpperCase() : null;
+  }
+
+  private static String getPath(QueryStringDecoder decoder)
+          throws FileNotFoundException {
+    String path = decoder.getPath();
+    if (path.startsWith("/webhdfs/v1/")) {
+      return path.substring(11);
+    } else {
+      throw new FileNotFoundException("Path: " + path + " should " +
+              "start with \"/webhdfs/v1/\"");
+    }
   }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/FSImageLoader.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/FSImageLoader.java
index bab83a132f3..b68d8425f43 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/FSImageLoader.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/FSImageLoader.java
@@ -18,16 +18,22 @@
 package org.apache.hadoop.hdfs.tools.offlineImageViewer;
 
 import java.io.BufferedInputStream;
+import java.io.EOFException;
 import java.io.FileInputStream;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.RandomAccessFile;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 
+import com.google.common.collect.ImmutableList;
+import com.google.protobuf.CodedInputStream;
+import com.google.protobuf.InvalidProtocolBufferException;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
@@ -55,14 +61,38 @@ import com.google.common.io.LimitInputStream;
 class FSImageLoader {
   public static final Log LOG = LogFactory.getLog(FSImageHandler.class);
 
-  private static String[] stringTable;
-  private static Map<Long, FsImageProto.INodeSection.INode> inodes =
-      Maps.newHashMap();
-  private static Map<Long, long[]> dirmap = Maps.newHashMap();
-  private static List<FsImageProto.INodeReferenceSection.INodeReference>
-      refList = Lists.newArrayList();
+  private final String[] stringTable;
+  // byte representation of inodes, sorted by id
+  private final byte[][] inodes;
+  private final Map<Long, long[]> dirmap;
+  private static final Comparator<byte[]> INODE_BYTES_COMPARATOR = new
+          Comparator<byte[]>() {
+    @Override
+    public int compare(byte[] o1, byte[] o2) {
+      try {
+        final FsImageProto.INodeSection.INode l = FsImageProto.INodeSection
+                .INode.parseFrom(o1);
+        final FsImageProto.INodeSection.INode r = FsImageProto.INodeSection
+                .INode.parseFrom(o2);
+        if (l.getId() < r.getId()) {
+          return -1;
+        } else if (l.getId() > r.getId()) {
+          return 1;
+        } else {
+          return 0;
+        }
+      } catch (InvalidProtocolBufferException e) {
+        throw new RuntimeException(e);
+      }
+    }
+  };
 
-  private FSImageLoader() {}
+  private FSImageLoader(String[] stringTable, byte[][] inodes,
+                        Map<Long, long[]> dirmap) {
+    this.stringTable = stringTable;
+    this.inodes = inodes;
+    this.dirmap = dirmap;
+  }
 
   /**
    * Load fsimage into the memory.
@@ -79,7 +109,14 @@ class FSImageLoader {
 
     FsImageProto.FileSummary summary = FSImageUtil.loadSummary(file);
     FileInputStream fin = null;
+
     try {
+      // Map to record INodeReference to the referred id
+      ImmutableList<Long> refIdList = null;
+      String[] stringTable = null;
+      byte[][] inodes = null;
+      Map<Long, long[]> dirmap = null;
+
       fin = new FileInputStream(file.getFD());
 
       ArrayList<FsImageProto.FileSummary.Section> sections =
@@ -109,34 +146,37 @@ class FSImageLoader {
             summary.getCodec(), new BufferedInputStream(new LimitInputStream(
             fin, s.getLength())));
 
+        LOG.debug("Loading section " + s.getName() + " length: " + s.getLength
+                ());
         switch (FSImageFormatProtobuf.SectionName.fromString(s.getName())) {
           case STRING_TABLE:
-            loadStringTable(is);
+            stringTable = loadStringTable(is);
             break;
           case INODE:
-            loadINodeSection(is);
+            inodes = loadINodeSection(is);
             break;
           case INODE_REFERENCE:
-            loadINodeReferenceSection(is);
+            refIdList = loadINodeReferenceSection(is);
             break;
           case INODE_DIR:
-            loadINodeDirectorySection(is);
+            dirmap = loadINodeDirectorySection(is, refIdList);
             break;
           default:
             break;
         }
       }
+      return new FSImageLoader(stringTable, inodes, dirmap);
     } finally {
       IOUtils.cleanup(null, fin);
     }
-    return new FSImageLoader();
   }
 
-  private static void loadINodeDirectorySection(InputStream in)
+  private static Map<Long, long[]> loadINodeDirectorySection
+          (InputStream in, List<Long> refIdList)
       throws IOException {
-    if (LOG.isDebugEnabled()) {
-      LOG.debug("Loading directory section");
-    }
+    LOG.info("Loading inode directory section");
+    Map<Long, long[]> dirs = Maps.newHashMap();
+    long counter = 0;
     while (true) {
       FsImageProto.INodeDirectorySection.DirEntry e =
           FsImageProto.INodeDirectorySection.DirEntry.parseDelimitedFrom(in);
@@ -144,31 +184,27 @@ class FSImageLoader {
       if (e == null) {
         break;
       }
+      ++counter;
+
       long[] l = new long[e.getChildrenCount() + e.getRefChildrenCount()];
       for (int i = 0; i < e.getChildrenCount(); ++i) {
         l[i] = e.getChildren(i);
       }
       for (int i = e.getChildrenCount(); i < l.length; i++) {
         int refId = e.getRefChildren(i - e.getChildrenCount());
-        l[i] = refList.get(refId).getReferredId();
-      }
-      dirmap.put(e.getParent(), l);
-      if (LOG.isDebugEnabled()) {
-        LOG.debug("Loaded directory (parent " + e.getParent()
-            + ") with " + e.getChildrenCount() + " children and "
-            + e.getRefChildrenCount() + " reference children");
+        l[i] = refIdList.get(refId);
       }
+      dirs.put(e.getParent(), l);
     }
-    if (LOG.isDebugEnabled()) {
-      LOG.debug("Loaded " + dirmap.size() + " directories");
-    }
+    LOG.info("Loaded " + counter + " directories");
+    return dirs;
   }
 
-  private static void loadINodeReferenceSection(InputStream in)
+  private static ImmutableList<Long> loadINodeReferenceSection(InputStream in)
       throws IOException {
-    if (LOG.isDebugEnabled()) {
-      LOG.debug("Loading inode reference section");
-    }
+    LOG.info("Loading inode references");
+    ImmutableList.Builder<Long> builder = ImmutableList.builder();
+    long counter = 0;
     while (true) {
       FsImageProto.INodeReferenceSection.INodeReference e =
           FsImageProto.INodeReferenceSection.INodeReference
@@ -176,49 +212,44 @@ class FSImageLoader {
       if (e == null) {
         break;
       }
-      refList.add(e);
-      if (LOG.isTraceEnabled()) {
-        LOG.trace("Loaded inode reference named '" + e.getName()
-            + "' referring to id " + e.getReferredId() + "");
-      }
-    }
-    if (LOG.isDebugEnabled()) {
-      LOG.debug("Loaded " + refList.size() + " inode references");
+      ++counter;
+      builder.add(e.getReferredId());
     }
+    LOG.info("Loaded " + counter + " inode references");
+    return builder.build();
   }
 
-  private static void loadINodeSection(InputStream in) throws IOException {
+  private static byte[][] loadINodeSection(InputStream in)
+          throws IOException {
     FsImageProto.INodeSection s = FsImageProto.INodeSection
         .parseDelimitedFrom(in);
-    if (LOG.isDebugEnabled()) {
-      LOG.debug("Found " + s.getNumInodes() + " inodes in inode section");
-    }
+    LOG.info("Loading " + s.getNumInodes() + " inodes.");
+    final byte[][] inodes = new byte[(int) s.getNumInodes()][];
+
     for (int i = 0; i < s.getNumInodes(); ++i) {
-      FsImageProto.INodeSection.INode p = FsImageProto.INodeSection.INode
-          .parseDelimitedFrom(in);
-      inodes.put(p.getId(), p);
-      if (LOG.isTraceEnabled()) {
-        LOG.trace("Loaded inode id " + p.getId() + " type " + p.getType()
-            + " name '" + p.getName().toStringUtf8() + "'");
-      }
+      int size = CodedInputStream.readRawVarint32(in.read(), in);
+      byte[] bytes = new byte[size];
+      IOUtils.readFully(in, bytes, 0, size);
+      inodes[i] = bytes;
     }
+    LOG.debug("Sorting inodes");
+    Arrays.sort(inodes, INODE_BYTES_COMPARATOR);
+    LOG.debug("Finished sorting inodes");
+    return inodes;
   }
 
-  private static void loadStringTable(InputStream in) throws IOException {
+  private static String[] loadStringTable(InputStream in) throws
+  IOException {
     FsImageProto.StringTableSection s = FsImageProto.StringTableSection
         .parseDelimitedFrom(in);
-    if (LOG.isDebugEnabled()) {
-      LOG.debug("Found " + s.getNumEntry() + " strings in string section");
-    }
-    stringTable = new String[s.getNumEntry() + 1];
+    LOG.info("Loading " + s.getNumEntry() + " strings");
+    String[] stringTable = new String[s.getNumEntry() + 1];
     for (int i = 0; i < s.getNumEntry(); ++i) {
       FsImageProto.StringTableSection.Entry e = FsImageProto
           .StringTableSection.Entry.parseDelimitedFrom(in);
       stringTable[e.getId()] = e.getStr();
-      if (LOG.isTraceEnabled()) {
-        LOG.trace("Loaded string " + e.getStr());
-      }
     }
+    return stringTable;
   }
 
   /**
@@ -229,7 +260,7 @@ class FSImageLoader {
    */
   String getFileStatus(String path) throws IOException {
     ObjectMapper mapper = new ObjectMapper();
-    FsImageProto.INodeSection.INode inode = inodes.get(getINodeId(path));
+    FsImageProto.INodeSection.INode inode = fromINodeId(lookup(path));
     return "{\"FileStatus\":\n"
         + mapper.writeValueAsString(getFileStatus(inode, false)) + "\n}\n";
   }
@@ -256,10 +287,11 @@ class FSImageLoader {
     return sb.toString();
   }
 
-  private List<Map<String, Object>> getFileStatusList(String path) {
+  private List<Map<String, Object>> getFileStatusList(String path)
+          throws IOException {
     List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
-    long id = getINodeId(path);
-    FsImageProto.INodeSection.INode inode = inodes.get(id);
+    long id = lookup(path);
+    FsImageProto.INodeSection.INode inode = fromINodeId(id);
     if (inode.getType() == FsImageProto.INodeSection.INode.Type.DIRECTORY) {
       if (!dirmap.containsKey(id)) {
         // if the directory is empty, return empty list
@@ -267,7 +299,7 @@ class FSImageLoader {
       }
       long[] children = dirmap.get(id);
       for (long cid : children) {
-        list.add(getFileStatus(inodes.get(cid), true));
+        list.add(getFileStatus(fromINodeId(cid), true));
       }
     } else {
       list.add(getFileStatus(inode, false));
@@ -305,9 +337,9 @@ class FSImageLoader {
     return sb.toString();
   }
 
-  private List<AclEntry> getAclEntryList(String path) {
-    long id = getINodeId(path);
-    FsImageProto.INodeSection.INode inode = inodes.get(id);
+  private List<AclEntry> getAclEntryList(String path) throws IOException {
+    long id = lookup(path);
+    FsImageProto.INodeSection.INode inode = fromINodeId(id);
     switch (inode.getType()) {
       case FILE: {
         FsImageProto.INodeSection.INodeFile f = inode.getFile();
@@ -325,9 +357,9 @@ class FSImageLoader {
     }
   }
 
-  private PermissionStatus getPermissionStatus(String path) {
-    long id = getINodeId(path);
-    FsImageProto.INodeSection.INode inode = inodes.get(id);
+  private PermissionStatus getPermissionStatus(String path) throws IOException {
+    long id = lookup(path);
+    FsImageProto.INodeSection.INode inode = fromINodeId(id);
     switch (inode.getType()) {
       case FILE: {
         FsImageProto.INodeSection.INodeFile f = inode.getFile();
@@ -353,30 +385,41 @@ class FSImageLoader {
   /**
    * Return the INodeId of the specified path.
    */
-  private long getINodeId(String strPath) {
-    if (strPath.equals("/")) {
-      return INodeId.ROOT_INODE_ID;
-    }
-
-    String[] nameList = strPath.split("/");
-    Preconditions.checkArgument(nameList.length > 1,
-                                "Illegal path: " + strPath);
+  private long lookup(String path) throws IOException {
+    Preconditions.checkArgument(path.startsWith("/"));
     long id = INodeId.ROOT_INODE_ID;
-    for (int i = 1; i < nameList.length; i++) {
-      long[] children = dirmap.get(id);
-      Preconditions.checkNotNull(children, "File: " +
-          strPath + " is not found in the fsimage.");
-      String cName = nameList[i];
-      boolean findChildren = false;
+    for (int offset = 0, next; offset < path.length(); offset = next) {
+      next = path.indexOf('/', offset + 1);
+      if (next == -1) {
+        next = path.length();
+      }
+      if (offset + 1 > next) {
+        break;
+      }
+
+      final String component = path.substring(offset + 1, next);
+
+      if (component.isEmpty()) {
+        continue;
+      }
+
+      final long[] children = dirmap.get(id);
+      if (children == null) {
+        throw new FileNotFoundException(path);
+      }
+
+      boolean found = false;
       for (long cid : children) {
-        if (cName.equals(inodes.get(cid).getName().toStringUtf8())) {
-          id = cid;
-          findChildren = true;
+        FsImageProto.INodeSection.INode child = fromINodeId(cid);
+        if (component.equals(child.getName().toStringUtf8())) {
+          found = true;
+          id = child.getId();
           break;
         }
       }
-      Preconditions.checkArgument(findChildren, "File: " +
-          strPath + " is not found in the fsimage.");
+      if (!found) {
+        throw new FileNotFoundException(path);
+      }
     }
     return id;
   }
@@ -460,4 +503,23 @@ class FSImageLoader {
   private String toString(FsPermission permission) {
     return String.format("%o", permission.toShort());
   }
+
+  private FsImageProto.INodeSection.INode fromINodeId(final long id)
+          throws IOException {
+    int l = 0, r = inodes.length;
+    while (l < r) {
+      int mid = l + (r - l) / 2;
+      FsImageProto.INodeSection.INode n = FsImageProto.INodeSection.INode
+              .parseFrom(inodes[mid]);
+      long nid = n.getId();
+      if (id > nid) {
+        l = mid + 1;
+      } else if (id < nid) {
+        r = mid;
+      } else {
+        return n;
+      }
+    }
+    return null;
+  }
 }