Parallel resource loading

https://bugs.eclipse.org/bugs/show_bug.cgi?id=358714

10 files changed, 1000 insertions, 363 deletions

diff --git a/plugins/org.eclipse.xtext.builder/META-INF/MANIFEST.MF b/plugins/org.eclipse.xtext.builder/META-INF/MANIFEST.MF
index 6dd9f9e..915d87a 100644
--- a/plugins/org.eclipse.xtext.builder/META-INF/MANIFEST.MF
+++ b/plugins/org.eclipse.xtext.builder/META-INF/MANIFEST.MF
@@ -16,7 +16,7 @@ Export-Package: org.eclipse.xtext.builder,
  org.eclipse.xtext.builder.impl.javasupport;x-friends:="org.eclipse.xtext.builder.tests,org.eclipse.xtext.ui.shared",
  org.eclipse.xtext.builder.internal;x-friends:="org.eclipse.xtext.builder.tests,org.eclipse.xtext.ui.shared",
  org.eclipse.xtext.builder.nature;x-friends:="org.eclipse.xtext.builder.tests,org.eclipse.xtext.ui.shared",
- org.eclipse.xtext.builder.preferences
+ org.eclipse.xtext.builder.resourceloader, org.eclipse.xtext.builder.preferences
 Require-Bundle: org.eclipse.xtext;bundle-version="2.0.0",
  org.eclipse.xtext.util;bundle-version="2.0.0",
  org.eclipse.emf.ecore;visibility:=reexport,
diff --git a/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/clustering/ClusteringBuilderState.java b/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/clustering/ClusteringBuilderState.java
index 6f8f146..fce1d2e 100644
--- a/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/clustering/ClusteringBuilderState.java
+++ b/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/clustering/ClusteringBuilderState.java
@@ -1,348 +1,436 @@
-/*******************************************************************************

- * Copyright (c) 2010 itemis AG (http://www.itemis.eu) and others.

- * All rights reserved. This program and the accompanying materials

- * are made available under the terms of the Eclipse Public License v1.0

- * which accompanies this distribution, and is available at

- * http://www.eclipse.org/legal/epl-v10.html

- *******************************************************************************/

-package org.eclipse.xtext.builder.clustering;

-

-import java.util.ArrayList;

-import java.util.Collection;

-import java.util.Collections;

-import java.util.Iterator;

-import java.util.List;

-import java.util.Queue;

-import java.util.Set;

-

-import org.apache.log4j.Logger;

-import org.eclipse.core.runtime.IProgressMonitor;

-import org.eclipse.core.runtime.OperationCanceledException;

-import org.eclipse.core.runtime.SubMonitor;

-import org.eclipse.emf.common.util.URI;

-import org.eclipse.emf.common.util.WrappedException;

-import org.eclipse.emf.ecore.resource.Resource;

-import org.eclipse.emf.ecore.resource.ResourceSet;

-import org.eclipse.xtext.EcoreUtil2;

-import org.eclipse.xtext.builder.builderState.AbstractBuilderState;

-import org.eclipse.xtext.builder.builderState.BuilderStateUtil;

-import org.eclipse.xtext.builder.builderState.ResourceDescriptionsData;

-import org.eclipse.xtext.builder.builderState.impl.ResourceDescriptionImpl;

-import org.eclipse.xtext.builder.impl.BuildData;

-import org.eclipse.xtext.resource.IResourceDescription;

-import org.eclipse.xtext.resource.IResourceDescription.Delta;

-import org.eclipse.xtext.resource.IResourceDescriptions;

-import org.eclipse.xtext.resource.IResourceServiceProvider;

-import org.eclipse.xtext.resource.impl.DefaultResourceDescriptionDelta;

-import org.eclipse.xtext.util.CancelIndicator;

-

-import com.google.common.collect.ImmutableList;

-import com.google.common.collect.Sets;

-import com.google.inject.Inject;

-

-/**

- * @author Sebastian Zarnekow - Initial contribution and API

- * @author Thomas Wolf <thomas.wolf@paranor.ch> - Refactored the build phases and documentation

- */

-public class ClusteringBuilderState extends AbstractBuilderState {

-

-	/** Class-wide logger. */

-    private static final Logger LOGGER = Logger.getLogger(ClusteringBuilderState.class);

-    

-    private static final int CLUSTER_SIZE = 20;

-

-    @Inject

-	private IResourceServiceProvider.Registry managerRegistry;

-

-	@Inject

-	private IResourceClusteringPolicy clusteringPolicy;

-

-	/**

-     * Actually do the build.

-     * 

-     * @param resourceSet

-     *            The resource set

-     * @param toBeUpdated

-     *            The URIs of all the resources that have physically changed

-     * @param toBeRemoved

-     *            The URIs of all the resources that have been physically deleted

-     * @param newMap

-     *            A map collecting the new resource descriptions as they are to be persisted. (The new index after the build.)

-     *            Initially contains the old resource descriptions.

-     * @param monitor

-     *            The progress monitor

-     * @return A list of deltas describing all changes made by the build.

-     */

-    @Override

-    protected Collection<Delta> doUpdate(BuildData buildData, ResourceDescriptionsData newData, IProgressMonitor monitor) {

-        final SubMonitor progress = SubMonitor.convert(monitor, 100);

-

-        

-        // Step 1: Clean the set of deleted URIs. If any of them are also added, they're not deleted.

-        final Set<URI> toBeDeleted = buildData.getAndRemoveToBeDeleted();

-

-        // Step 2: Create a new state (old state minus the deleted resources). This, by virtue of the flag 

-        // NAMED_BUILDER_SCOPE in the resource set's load options

-        // and a Guice binding, is the index that is used during the build; i.e., linking during the build will

-        // use this. Once the build is completed, the persistable index is reset to the contents of newState by

-        // virtue of the newMap, which is maintained in synch with this.

-        ResourceSet resourceSet = buildData.getResourceSet();

-        final CurrentDescriptions newState = new CurrentDescriptions(resourceSet, newData);

-

-        // Step 3: Create a queue; write new temporary resource descriptions for the added or updated resources so that we can link

-        // subsequently; put all the added or updated resources into the queue.

-        writeNewResourceDescriptions(buildData, this, newState, progress.newChild(20));

-

-        if (progress.isCanceled()) {

-            throw new OperationCanceledException();

-        }

-

-        // Step 4: Create a URI set of resources not yet in the delta. This is used for queuing; whenever a resource is

-        // queued for processing, its URI is removed from this set. queueAffectedResources will consider only resources

-        // in this set as potential candidates.

-        for (final URI uri : toBeDeleted) {

-        	newData.removeDescription(uri);

-        }

-        final Set<URI> allRemainingURIs = Sets.newLinkedHashSet(newData.getAllURIs());

-        allRemainingURIs.removeAll(buildData.getToBeUpdated());

-        for(URI remainingURI: buildData.getAllRemainingURIs()) {

-        	allRemainingURIs.remove(remainingURI);

-        }

-        // TODO: consider to remove any entry from upstream projects and independent projects

-        // from the set of remaining uris (template method or service?)

-        // this should reduce the number of to-be-checked descriptions significantly

-        // for common setups (large number of reasonable sized projects)

-

-        // Our return value. It contains all the deltas resulting from this build.

-        final Set<Delta> allDeltas = Sets.newHashSet();

-        

-        // Step 5: Put all resources depending on a deleted resource into the queue. Also register the deltas in allDeltas.

-        if (!toBeDeleted.isEmpty()) {

-            for (final URI uri : toBeDeleted) {

-                final IResourceDescription oldDescription = this.getResourceDescription(uri);

-                if (oldDescription != null) {

-                    allDeltas.add(new DefaultResourceDescriptionDelta(oldDescription, null));

-                }

-            }

-        }

-        // Add all pending deltas to all deltas (may be scheduled java deltas)

-        Collection<Delta> pendingDeltas = buildData.getAndRemovePendingDeltas();

-        allDeltas.addAll(pendingDeltas);

-        queueAffectedResources(allRemainingURIs, this, newState, allDeltas, buildData, progress.newChild(1));

-        

-        // Step 6: Iteratively got through the queue. For each resource, create a new resource description and queue all depending

-        // resources that are not yet in the delta. Validate resources. Do this in chunks.

-        final SubMonitor subProgress = progress.newChild(80);

-        CancelIndicator cancelMonitor = new CancelIndicator() {

-            public boolean isCanceled() {

-                return progress.isCanceled();

-            }

-        };

-

-        int index = 1;

-        Queue<URI> queue = buildData.getURIQueue();

-        while (!queue.isEmpty()) {

-            subProgress.setWorkRemaining(queue.size() + 2);

-            // TODO: How to properly do progress indication with an unknown amount of work? Somehow, the progress bar doesn't

-            // advance anymore after this...

-            final List<Delta> newDeltas = new ArrayList<Delta>(CLUSTER_SIZE);

-            final List<Delta> changedDeltas = new ArrayList<Delta>(CLUSTER_SIZE);

-            while (!queue.isEmpty()) {

-                if (subProgress.isCanceled()) {

-                    throw new OperationCanceledException();

-                }

-                if (!clusteringPolicy.continueProcessing(resourceSet, queue.peek(), newDeltas.size())) {

-                	break;

-                }

-                final URI changedURI = queue.poll();

-                if (!toBeDeleted.contains(changedURI)) {

-	                subProgress.subTask("Updating resource description for " + changedURI.lastSegment() + " (" + index + " of " + (index + queue.size()) + ")");

-	                // Load the resource and create a new resource description

-	                Resource resource = null;

-	                Delta newDelta = null;

-	                try {

-	                    final IResourceDescription.Manager manager = getResourceDescriptionManager(changedURI);

-	                    if (manager != null) {

-	                        resource = resourceSet.getResource(changedURI, true);

-	                        // Resolve links here!

-							EcoreUtil2.resolveLazyCrossReferences(resource, cancelMonitor);

-	                        final IResourceDescription description = manager.getResourceDescription(resource);

-	                        final IResourceDescription copiedDescription = BuilderStateUtil.create(description);

-	                        newDelta = manager.createDelta(

-	                                    this.getResourceDescription(changedURI), copiedDescription);

-	                    }

-	                } catch (final WrappedException ex) {

-	                    LOGGER.error("Error loading resource from: " + changedURI.toString(), ex); //$NON-NLS-1$

-	                    if (resource != null) {

-	                        resourceSet.getResources().remove(resource);

-	                    }

-	                    final IResourceDescription oldDescription = this.getResourceDescription(changedURI);

-	                    final IResourceDescription newDesc = newState.getResourceDescription(changedURI);

-	                    ResourceDescriptionImpl indexReadyDescription = newDesc != null ? BuilderStateUtil.create(newDesc) : null;

-	                    if ((oldDescription != null || indexReadyDescription != null) && oldDescription != indexReadyDescription) {

-							newDelta = new DefaultResourceDescriptionDelta(oldDescription, indexReadyDescription);

-	                    }

-	                }

-	                if (newDelta != null) {

-	                    newDeltas.add(newDelta);

-	                    if (newDelta.haveEObjectDescriptionsChanged())

-	                    	changedDeltas.add(newDelta);

-	                    // Make the new resource description known and update the map.

-	                    newState.register(newDelta);

-	                }

-	                subProgress.worked(1);

-	                index++;

-                }

-            }

-            queueAffectedResources(allRemainingURIs, this, newState, changedDeltas, buildData, subProgress.newChild(1));

-            // Validate now.

-            updateMarkers(resourceSet, ImmutableList.<Delta>copyOf(newDeltas), subProgress.newChild(1));

-            allDeltas.addAll(newDeltas);

-            // Release memory

-            if (!queue.isEmpty())

-				clearResourceSet(resourceSet);

-        }

-        return allDeltas;

-    }

-    

-    /**

-     * Create new resource descriptions for a set of resources given by their URIs.

-     * 

-     * @param resourceSet

-     *            The resource set

-     * @param oldState

-     *            The old index

-     * @param newState

-     *            The new index

-     * @param toBeUpdated

-     *            URIs of all resources physically changed (initial delta)

-     * @param monitor

-     *            The progress monitor used for user feedback

-     * @return A list of all the URIs of toBeUpdated that could be indeed loaded and for which new description were written.

-     */

-    protected void writeNewResourceDescriptions(

-            BuildData buildData,

-            IResourceDescriptions oldState,

-            CurrentDescriptions newState,

-            final IProgressMonitor monitor) {

-        int index = 1;

-        Collection<URI> toBeUpdated = buildData.getToBeUpdated();

-        ResourceSet resourceSet = buildData.getResourceSet();

-        final int n = toBeUpdated.size();

-        final SubMonitor subMonitor = SubMonitor.convert(monitor, "Write new resource descriptions", n); // TODO: NLS

-        for (final URI uri : toBeUpdated) {

-            if (subMonitor.isCanceled()) {

-                throw new OperationCanceledException();

-            }

-            subMonitor.subTask("Writing new resource description for " + uri.lastSegment() + " (" + index + " of " + n + ")"); // TODO: NLS

-            Resource resource = null;

-            try {

-                resource = resourceSet.getResource(uri, true);

-

-                final IResourceDescription.Manager manager = getResourceDescriptionManager(uri);

-                if (manager != null) {

-                    // We don't care here about links, we really just want the exported objects so that we can link in the

-                    // next phase.

-                    final IResourceDescription description = manager.getResourceDescription(resource);

-                    final IResourceDescription copiedDescription = new CopiedResourceDescription(description);

-                    // We also don't care what kind of Delta we get here; it's just a temporary transport vehicle. That interface

-                    // could do with some clean-up, too, because all we actually want to do is register the new resource

-                    // description, not the delta.

-                    newState.register(new DefaultResourceDescriptionDelta(oldState.getResourceDescription(uri), copiedDescription));

-                    buildData.queueURI(uri);

-                }

-            } catch (final WrappedException ex) {

-                if (resourceSet.getURIConverter().exists(uri, Collections.emptyMap())) {

-                    LOGGER.error("Error loading resource from: " + uri.toString(), ex); //$NON-NLS-1$

-                }

-                if (resource != null) {

-                    resourceSet.getResources().remove(resource);

-                }

-                final IResourceDescription oldDescription = oldState.getResourceDescription(uri);

-                if (oldDescription != null) {

-                    newState.register(new DefaultResourceDescriptionDelta(oldDescription, null));

-                }

-                // If we couldn't load it, there's no use trying again: do not add it to the queue

-            }

-

-            subMonitor.worked(1);

-            index++;

-            if (index % CLUSTER_SIZE == 0) {

-                resourceSet.getResources().clear();

-            }

-        }

-        clearResourceSet(resourceSet);

-    }

-

-    /**

-     * Clears the content of the resource set without sending notifications.

-     * This avoids unnecessary, explicit unloads.

-     */

-	protected void clearResourceSet(ResourceSet resourceSet) {

-		boolean wasDeliver = resourceSet.eDeliver();

-		try {

-			resourceSet.eSetDeliver(false);

-			resourceSet.getResources().clear();

-		} finally {

-			resourceSet.eSetDeliver(wasDeliver);

-		}

-	}

-

-    /**

-     * Put all resources that depend on some changes onto the queue of resources to be processed. 

-     * Updates notInDelta by removing all URIs put into the queue.

-     * 

-     * @param notInDelta

-     *            URIs of unchanged and unaffected resources

-     * @param oldState

-     *            State before the build

-     * @param newState

-     *            The current state

-     * @param deltas

-     *            The changes

-     * @param queue

-     *            The queue of resources yet to be built

-     * @param monitor

-     *            The progress monitor used for user feedback

-     */

-    protected void queueAffectedResources(

-    		Set<URI> allRemainingURIs, 

-    		IResourceDescriptions oldState, 

-    		CurrentDescriptions newState,

-            Collection<Delta> deltas, 

-            BuildData buildData, 

-            final IProgressMonitor monitor) {

-    	if (deltas.isEmpty()) {

-            return;

-        }

-        final SubMonitor progress = SubMonitor.convert(monitor, allRemainingURIs.size());

-        Iterator<URI> iter = allRemainingURIs.iterator();

-        while (iter.hasNext()) {

-            if (progress.isCanceled()) {

-                throw new OperationCanceledException();

-            }

-            final URI candidateURI = iter.next();

-            final IResourceDescription candidateDescription = oldState.getResourceDescription(candidateURI);

-            final IResourceDescription.Manager manager = getResourceDescriptionManager(candidateURI);

-            if (candidateDescription == null || manager == null) {

-                // If there is no description in the old state, there's no need to re-check this over and over.

-                iter.remove();

-            } else {

-                if (manager.isAffected(deltas, candidateDescription, newState)) {

-                    buildData.queueURI(candidateURI);

-                    iter.remove();

-                }

-            }

-            progress.worked(1);

-        }

-    }

-

-	protected IResourceDescription.Manager getResourceDescriptionManager(URI uri) {

-		IResourceServiceProvider resourceServiceProvider = managerRegistry.getResourceServiceProvider(uri);

-		if (resourceServiceProvider == null) {

-			return null;

-		}

-		return resourceServiceProvider.getResourceDescriptionManager();

-	}

-

-}

+/*******************************************************************************
+ * Copyright (c) 2010 itemis AG (http://www.itemis.eu) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *******************************************************************************/
+package org.eclipse.xtext.builder.clustering;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Queue;
+import java.util.Set;
+
+import org.apache.log4j.Logger;
+import org.eclipse.core.runtime.IProgressMonitor;
+import org.eclipse.core.runtime.OperationCanceledException;
+import org.eclipse.core.runtime.SubMonitor;
+import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.common.util.WrappedException;
+import org.eclipse.emf.ecore.resource.Resource;
+import org.eclipse.emf.ecore.resource.ResourceSet;
+import org.eclipse.xtext.EcoreUtil2;
+import org.eclipse.xtext.builder.builderState.AbstractBuilderState;
+import org.eclipse.xtext.builder.builderState.BuilderStateUtil;
+import org.eclipse.xtext.builder.builderState.ResourceDescriptionsData;
+import org.eclipse.xtext.builder.builderState.impl.ResourceDescriptionImpl;
+import org.eclipse.xtext.builder.impl.BuildData;
+import org.eclipse.xtext.builder.resourceloader.IResourceLoader;
+import org.eclipse.xtext.builder.resourceloader.IResourceLoader.LoadOperation;
+import org.eclipse.xtext.builder.resourceloader.IResourceLoader.LoadOperationException;
+import org.eclipse.xtext.resource.IResourceDescription;
+import org.eclipse.xtext.resource.IResourceDescription.Delta;
+import org.eclipse.xtext.resource.IResourceDescriptions;
+import org.eclipse.xtext.resource.IResourceServiceProvider;
+import org.eclipse.xtext.resource.impl.DefaultResourceDescriptionDelta;
+import org.eclipse.xtext.util.CancelIndicator;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
+import com.google.inject.Inject;
+import com.google.inject.name.Named;
+
+/**
+ * @author Sebastian Zarnekow - Initial contribution and API
+ * @author Thomas Wolf <thomas.wolf@paranor.ch> - Refactored the build phases and documentation
+ * @author Lieven Lemiengre <lieven.lemiengre@sigasi.com> - Parallel resource loading
+ */
+public class ClusteringBuilderState extends AbstractBuilderState {
+
+    public static final String RESOURCELOADER_CROSS_LINKING = "org.eclipse.xtext.builder.resourceloader.crossLinking";
+
+    public static final String RESOURCELOADER_GLOBAL_INDEX = "org.eclipse.xtext.builder.resourceloader.globalIndex";
+
+    /** Class-wide logger. */
+    private static final Logger LOGGER = Logger.getLogger(ClusteringBuilderState.class);
+
+    @Inject
+    private IResourceServiceProvider.Registry managerRegistry;
+
+    @Inject
+    private IResourceClusteringPolicy clusteringPolicy;
+
+    @Inject
+    @Named(RESOURCELOADER_GLOBAL_INDEX)
+    private IResourceLoader globalIndexResourceLoader;
+
+    @Inject
+    @Named(RESOURCELOADER_CROSS_LINKING)
+    private IResourceLoader crossLinkingResourceLoader;
+
+    /**
+     * Actually do the build.
+     *
+     * @param resourceSet
+     *            The resource set
+     * @param toBeUpdated
+     *            The URIs of all the resources that have physically changed
+     * @param toBeRemoved
+     *            The URIs of all the resources that have been physically deleted
+     * @param newMap
+     *            A map collecting the new resource descriptions as they are to be persisted. (The new index after the build.)
+     *            Initially contains the old resource descriptions.
+     * @param monitor
+     *            The progress monitor
+     * @return A list of deltas describing all changes made by the build.
+     */
+    @Override
+    protected Collection<Delta> doUpdate(BuildData buildData, ResourceDescriptionsData newData, IProgressMonitor monitor) {
+        final SubMonitor progress = SubMonitor.convert(monitor, 100);
+
+
+        // Step 1: Clean the set of deleted URIs. If any of them are also added, they're not deleted.
+        final Set<URI> toBeDeleted = buildData.getAndRemoveToBeDeleted();
+
+        // Step 2: Create a new state (old state minus the deleted resources). This, by virtue of the flag
+        // NAMED_BUILDER_SCOPE in the resource set's load options
+        // and a Guice binding, is the index that is used during the build; i.e., linking during the build will
+        // use this. Once the build is completed, the persistable index is reset to the contents of newState by
+        // virtue of the newMap, which is maintained in synch with this.
+        ResourceSet resourceSet = buildData.getResourceSet();
+        final CurrentDescriptions newState = new CurrentDescriptions(resourceSet, newData);
+
+        // Step 3: Create a queue; write new temporary resource descriptions for the added or updated resources so that we can link
+        // subsequently; put all the added or updated resources into the queue.
+        writeNewResourceDescriptions(buildData, this, newState, progress.newChild(20));
+
+        if (progress.isCanceled()) {
+            throw new OperationCanceledException();
+        }
+
+        // Step 4: Create a URI set of resources not yet in the delta. This is used for queuing; whenever a resource is
+        // queued for processing, its URI is removed from this set. queueAffectedResources will consider only resources
+        // in this set as potential candidates.
+        for (final URI uri : toBeDeleted) {
+            newData.removeDescription(uri);
+        }
+        final Set<URI> allRemainingURIs = Sets.newLinkedHashSet(newData.getAllURIs());
+        allRemainingURIs.removeAll(buildData.getToBeUpdated());
+        for(URI remainingURI: buildData.getAllRemainingURIs()) {
+            allRemainingURIs.remove(remainingURI);
+        }
+        // TODO: consider to remove any entry from upstream projects and independent projects
+        // from the set of remaining uris (template method or service?)
+        // this should reduce the number of to-be-checked descriptions significantly
+        // for common setups (large number of reasonable sized projects)
+
+        // Our return value. It contains all the deltas resulting from this build.
+        final Set<Delta> allDeltas = Sets.newHashSet();
+
+        // Step 5: Put all resources depending on a deleted resource into the queue. Also register the deltas in allDeltas.
+        if (!toBeDeleted.isEmpty()) {
+            for (final URI uri : toBeDeleted) {
+                final IResourceDescription oldDescription = this.getResourceDescription(uri);
+                if (oldDescription != null) {
+                    allDeltas.add(new DefaultResourceDescriptionDelta(oldDescription, null));
+                }
+            }
+        }
+        // Add all pending deltas to all deltas (may be scheduled java deltas)
+        Collection<Delta> pendingDeltas = buildData.getAndRemovePendingDeltas();
+        allDeltas.addAll(pendingDeltas);
+        queueAffectedResources(allRemainingURIs, this, newState, allDeltas, buildData, progress.newChild(1));
+
+        LoadOperation loadOperation = null;
+        try {
+            Queue<URI> queue = buildData.getURIQueue();
+            loadOperation = crossLinkingResourceLoader.create(resourceSet);
+            loadOperation.load(queue);
+
+            // Step 6: Iteratively got through the queue. For each resource, create a new resource description and queue all depending
+            // resources that are not yet in the delta. Validate resources. Do this in chunks.
+            final SubMonitor subProgress = progress.newChild(80);
+            CancelIndicator cancelMonitor = new CancelIndicator() {
+                public boolean isCanceled() {
+                    return progress.isCanceled();
+                }
+            };
+
+            int index = 1;
+            while (!queue.isEmpty()) {
+                subProgress.setWorkRemaining(queue.size() + 2);
+                // TODO: How to properly do progress indication with an unknown amount of work? Somehow, the progress bar doesn't
+                // advance anymore after this...
+                final List<Delta> newDeltas = Lists.newArrayList();
+                final List<Delta> changedDeltas = Lists.newArrayList();
+                while (!queue.isEmpty()) {
+                    if (subProgress.isCanceled()) {
+                        loadOperation.cancel();
+                        throw new OperationCanceledException();
+                    }
+                    if (!clusteringPolicy.continueProcessing(resourceSet, null, newDeltas.size())) {
+                        break;
+                    }
+
+                    URI changedURI = null;
+                    Resource resource = null;
+                    Delta newDelta = null;
+
+                    try {
+                        // Load the resource and create a new resource description
+                        Resource loadResult = loadOperation.next();
+                        changedURI = loadResult.getURI();
+                        resource = addResource(loadResult, resourceSet);
+
+                        subProgress.subTask("Updating resource description for " + changedURI.lastSegment() + " (" + index + " of " + (index + queue.size()) + ")");
+                        queue.remove(changedURI);
+                        if(toBeDeleted.contains(changedURI)) {
+                            break;
+                        }
+
+                        final IResourceDescription.Manager manager = getResourceDescriptionManager(changedURI);
+                        if (manager != null) {
+                            // Resolve links here!
+                            EcoreUtil2.resolveLazyCrossReferences(resource, cancelMonitor);
+                            final IResourceDescription description = manager.getResourceDescription(resource);
+                            final IResourceDescription copiedDescription = BuilderStateUtil.create(description);
+                            newDelta = manager.createDelta(this.getResourceDescription(changedURI), copiedDescription);
+                        }
+                    } catch (final WrappedException ex) {
+                        if(ex instanceof LoadOperationException) {
+                            changedURI = ((LoadOperationException) ex).getUri();
+                        }
+                        if(changedURI == null) {
+                            LOGGER.error("Error loading resource", ex); //$NON-NLS-1$
+                        } else {
+                            queue.remove(changedURI);
+                            if(toBeDeleted.contains(changedURI)) break;
+                            LOGGER.error("Error loading resource from: " + changedURI.toString(), ex); //$NON-NLS-1$
+                            if (resource != null) {
+                                resourceSet.getResources().remove(resource);
+                            }
+                            final IResourceDescription oldDescription = this.getResourceDescription(changedURI);
+                            final IResourceDescription newDesc = newState.getResourceDescription(changedURI);
+                            ResourceDescriptionImpl indexReadyDescription = newDesc != null ? BuilderStateUtil.create(newDesc) : null;
+                            if ((oldDescription != null || indexReadyDescription != null) && oldDescription != indexReadyDescription) {
+                                newDelta = new DefaultResourceDescriptionDelta(oldDescription, indexReadyDescription);
+                            }
+                        }
+                    }
+                    if (newDelta != null) {
+                        newDeltas.add(newDelta);
+                        if (newDelta.haveEObjectDescriptionsChanged())
+                            changedDeltas.add(newDelta);
+                        // Make the new resource description known and update the map.
+                        newState.register(newDelta);
+                    }
+                    subProgress.worked(1);
+                    index++;
+                }
+
+                loadOperation.cancel();
+
+                queueAffectedResources(allRemainingURIs, this, newState, changedDeltas, buildData, subProgress.newChild(1));
+
+                if(queue.size() > 0) {
+                    loadOperation = crossLinkingResourceLoader.create(resourceSet);
+                    loadOperation.load(queue);
+                }
+
+                // Validate now.
+                updateMarkers(resourceSet, ImmutableList.<Delta>copyOf(newDeltas), subProgress.newChild(1));
+                allDeltas.addAll(newDeltas);
+                // Release memory
+                if (!queue.isEmpty())
+                    clearResourceSet(resourceSet);
+            }
+        } finally {
+            if(loadOperation != null) loadOperation.cancel();
+        }
+        return allDeltas;
+    }
+
+    /**
+     * Create new resource descriptions for a set of resources given by their URIs.
+     *
+     * @param resourceSet
+     *            The resource set
+     * @param oldState
+     *            The old index
+     * @param newState
+     *            The new index
+     * @param toBeUpdated
+     *            URIs of all resources physically changed (initial delta)
+     * @param monitor
+     *            The progress monitor used for user feedback
+     * @return A list of all the URIs of toBeUpdated that could be indeed loaded and for which new description were written.
+     */
+    protected void writeNewResourceDescriptions(
+            BuildData buildData,
+            IResourceDescriptions oldState,
+            CurrentDescriptions newState,
+            final IProgressMonitor monitor) {
+        int index = 0;
+        Collection<URI> toBeUpdated = buildData.getToBeUpdated();
+        ResourceSet resourceSet = buildData.getResourceSet();
+        final int n = toBeUpdated.size();
+        final SubMonitor subMonitor = SubMonitor.convert(monitor, "Write new resource descriptions", n); // TODO: NLS
+
+        LoadOperation loadOperation = null;
+        try {
+            loadOperation = globalIndexResourceLoader.create(resourceSet);
+            loadOperation.load(toBeUpdated);
+
+            while (loadOperation.hasNext()) {
+                if (subMonitor.isCanceled()) {
+                    loadOperation.cancel();
+                    throw new OperationCanceledException();
+                }
+
+                if (!clusteringPolicy.continueProcessing(resourceSet, null, index)) {
+                    clearResourceSet(resourceSet);
+                }
+
+                URI uri = null;
+                Resource resource = null;
+                try {
+                    Resource loadResult = loadOperation.next();
+                    uri = loadResult.getURI();
+                    resource = addResource(loadResult, resourceSet);
+
+                    subMonitor.subTask("Writing new resource description for " + uri.lastSegment() + " (" + index++ + " of " + n + ")"); // TODO: NLS
+
+                    final IResourceDescription.Manager manager = getResourceDescriptionManager(uri);
+                    if (manager != null) {
+                        // We don't care here about links, we really just want the exported objects so that we can link in the
+                        // next phase.
+                        final IResourceDescription description = manager.getResourceDescription(resource);
+                        final IResourceDescription copiedDescription = new CopiedResourceDescription(description);
+                        // We also don't care what kind of Delta we get here; it's just a temporary transport vehicle. That interface
+                        // could do with some clean-up, too, because all we actually want to do is register the new resource
+                        // description, not the delta.
+                        newState.register(new DefaultResourceDescriptionDelta(oldState.getResourceDescription(uri), copiedDescription));
+                        buildData.queueURI(uri);
+                    }
+                } catch (final WrappedException ex) {
+                    if(ex instanceof LoadOperationException) {
+                        uri = ((LoadOperationException) ex).getUri();
+                    }
+                    if (uri == null) {
+                        LOGGER.error("Error loading resource", ex); //$NON-NLS-1$
+                    } else {
+                        if (resourceSet.getURIConverter().exists(uri, Collections.emptyMap())) {
+                            LOGGER.error("Error loading resource from: " + uri.toString(), ex); //$NON-NLS-1$
+                        }
+                        if (resource != null) {
+                            resourceSet.getResources().remove(resource);
+                        }
+                        final IResourceDescription oldDescription = oldState.getResourceDescription(uri);
+                        if (oldDescription != null) {
+                            newState.register(new DefaultResourceDescriptionDelta(oldDescription, null));
+                        }
+                    }
+                    // If we couldn't load it, there's no use trying again: do not add it to the queue
+                }
+
+                subMonitor.worked(1);
+            }
+        } finally {
+            if(loadOperation != null) loadOperation.cancel();
+        }
+    }
+
+    /**
+     * Clears the content of the resource set without sending notifications.
+     * This avoids unnecessary, explicit unloads.
+     */
+    protected void clearResourceSet(ResourceSet resourceSet) {
+        boolean wasDeliver = resourceSet.eDeliver();
+        try {
+            resourceSet.eSetDeliver(false);
+            resourceSet.getResources().clear();
+        } finally {
+            resourceSet.eSetDeliver(wasDeliver);
+        }
+    }
+
+    /**
+     * Adds a resource to the ResourceSet if the ResourceSet doesn't contain it yet.
+     *
+     * @param resource the resource
+     * @param resourceSet the resource set
+     * @return the resource
+     */
+    protected Resource addResource(Resource resource, ResourceSet resourceSet) {
+        URI uri = resource.getURI();
+        Resource r = resourceSet.getResource(uri, false);
+        if (r == null) {
+            resourceSet.getResources().add(resource);
+            return resource;
+        } else {
+            return r;
+        }
+    }
+
+    /**
+     * Put all resources that depend on some changes onto the queue of resources to be processed.
+     * Updates notInDelta by removing all URIs put into the queue.
+     *
+     * @param notInDelta
+     *            URIs of unchanged and unaffected resources
+     * @param oldState
+     *            State before the build
+     * @param newState
+     *            The current state
+     * @param deltas
+     *            The changes
+     * @param queue
+     *            The queue of resources yet to be built
+     * @param monitor
+     *            The progress monitor used for user feedback
+     */
+    protected void queueAffectedResources(
+            Set<URI> allRemainingURIs,
+            IResourceDescriptions oldState,
+            CurrentDescriptions newState,
+            Collection<Delta> deltas,
+            BuildData buildData,
+            final IProgressMonitor monitor) {
+        if (deltas.isEmpty()) {
+            return;
+        }
+        final SubMonitor progress = SubMonitor.convert(monitor, allRemainingURIs.size());
+        Iterator<URI> iter = allRemainingURIs.iterator();
+        while (iter.hasNext()) {
+            if (progress.isCanceled()) {
+                throw new OperationCanceledException();
+            }
+            final URI candidateURI = iter.next();
+            final IResourceDescription candidateDescription = oldState.getResourceDescription(candidateURI);
+            final IResourceDescription.Manager manager = getResourceDescriptionManager(candidateURI);
+            if (candidateDescription == null || manager == null) {
+                // If there is no description in the old state, there's no need to re-check this over and over.
+                iter.remove();
+            } else {
+                if (manager.isAffected(deltas, candidateDescription, newState)) {
+                    buildData.queueURI(candidateURI);
+                    iter.remove();
+                }
+            }
+            progress.worked(1);
+        }
+    }
+
+    protected IResourceDescription.Manager getResourceDescriptionManager(URI uri) {
+        IResourceServiceProvider resourceServiceProvider = managerRegistry.getResourceServiceProvider(uri);
+        if (resourceServiceProvider == null) {
+            return null;
+        }
+        return resourceServiceProvider.getResourceDescriptionManager();
+    }
+
+}
diff --git a/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/AbstractResourceLoader.java b/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/AbstractResourceLoader.java
new file mode 100644
index 0000000..2228156
--- a/dev/null
+++ b/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/AbstractResourceLoader.java
@@ -0,0 +1,94 @@
+/*******************************************************************************
+ * Copyright (c) 2011 Sigasi NV (http://www.sigasi.com) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *******************************************************************************/
+package org.eclipse.xtext.builder.resourceloader;
+
+import java.util.Collection;
+
+import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.ecore.resource.Resource;
+import org.eclipse.emf.ecore.resource.ResourceSet;
+import org.eclipse.xtext.resource.XtextResourceSet;
+
+import com.google.inject.Provider;
+
+
+/**
+ * @author Lieven Lemiengre - Initial contribution and API
+ * @since 2.1
+ */
+public abstract class AbstractResourceLoader implements IResourceLoader {
+
+	private final Provider<XtextResourceSet> resourceSetProvider;
+	private final Sorter sorter;
+
+	public AbstractResourceLoader(Provider<XtextResourceSet> resourceSetProvider, Sorter sorter) {
+		this.resourceSetProvider = resourceSetProvider;
+		this.sorter = sorter;
+	}
+
+	public Provider<XtextResourceSet> getResourceSetProvider() {
+		return resourceSetProvider;
+	}
+
+	public Sorter getSorter() {
+		return sorter;
+	}
+
+	protected Resource loadResource(URI uri, ResourceSet localResourceSet, ResourceSet parentResourceSet) {
+		return localResourceSet.getResource(uri, true);
+	}
+
+	protected class CheckedLoadOperation implements LoadOperation {
+
+		private final LoadOperation parent;
+		private boolean isLoading = false;
+		private boolean isCancelled = false;
+
+		public CheckedLoadOperation(LoadOperation parent) {
+			this.parent = parent;
+		}
+
+		public void load(Collection<URI> uris) {
+			if(isLoading) {
+				throw new IllegalStateException("The load operation has already been started.");
+			}
+			isLoading = true;
+			parent.load(uris);
+		}
+
+		public boolean hasNext() {
+			checkIsLoading();
+			checkIsNotCancelled();
+			return parent.hasNext();
+		}
+
+		public Resource next() throws LoadOperationException {
+			checkIsLoading();
+			checkIsNotCancelled();
+			return parent.next();
+		}
+
+		public Collection<URI> cancel() {
+			checkIsLoading();
+			isCancelled = true;
+			return parent.cancel();
+		}
+
+		private void checkIsLoading() {
+			if(!isLoading) {
+				throw new IllegalStateException("The load operation hasn't started yet.");
+			}
+		}
+
+		private void checkIsNotCancelled() {
+			if(isCancelled) {
+				throw new IllegalStateException("The load operation was cancelled.");
+			}
+		}
+	}
+}
diff --git a/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/IResourceLoader.java b/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/IResourceLoader.java
new file mode 100644
index 0000000..467ad2a
--- a/dev/null
+++ b/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/IResourceLoader.java
@@ -0,0 +1,131 @@
+/*******************************************************************************
+ * Copyright (c) 2011 Sigasi NV (http://www.sigasi.com) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *******************************************************************************/
+package org.eclipse.xtext.builder.resourceloader;
+
+import java.util.Collection;
+
+import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.common.util.WrappedException;
+import org.eclipse.emf.ecore.resource.Resource;
+import org.eclipse.emf.ecore.resource.ResourceSet;
+
+import com.google.common.collect.Lists;
+import com.google.inject.ImplementedBy;
+
+/**
+ *
+ * @author Lieven Lemiengre - Initial contribution and API
+ * @since 2.1
+ */
+@ImplementedBy(SerialResourceLoader.class)
+public interface IResourceLoader {
+
+	/**
+	 * Create a LoadOperation.
+	 * Be careful, while the load operation is running the parent ResourceSet may be read from different threads.
+	 * Synchronize on the parent ResourceSet when you interact with it!
+	 *
+	 * @param parent the parent ResourceSet
+	 * @return a LoadOperation
+	 */
+	LoadOperation create(ResourceSet parent);
+
+	/**
+	 * The Interface LoadOperation.
+	 */
+	interface LoadOperation {
+
+		/**
+		 * Load the resources.
+		 *
+		 * @param uris the uris
+		 * @throws IllegalStateException If the loading was already started or it was cancelled
+		 */
+		void load(Collection<URI> uris);
+
+		/**
+		 * Checks if the ResourceLoader is still processing resources.
+		 *
+		 * @return true, if successful
+		 * @throws IllegalStateException If the loading was cancelled or it hasn't started yet.
+		 */
+		boolean hasNext();
+
+
+		/**
+		 * Get the next Resource.
+		 * This is a blocking call, it returns the next resource that was finished processing.
+		 *
+		 * @return the next available resource
+		 * @throws IllegalStateException If the loading was cancelled or it hasn't started yet.
+		 * @throws LoadOperationException the load operation exception
+		 */
+		Resource next() throws LoadOperationException;
+
+		/**
+		 * Cancel loading the resources. This method can be executed multiple times.
+		 *
+		 * @return the collection
+		 */
+		Collection<URI> cancel();
+
+	}
+
+	@ImplementedBy(org.eclipse.xtext.builder.resourceloader.IResourceLoader.Sorter.NoSorting.class)
+	interface Sorter {
+		Collection<URI> sort(Collection<URI> uris);
+
+		class NoSorting implements Sorter {
+			public Collection<URI> sort(Collection<URI> uris) {
+				return Lists.newArrayList(uris);
+			}
+		}
+	}
+
+	/**
+	 * The Class LoadOperationException.
+	 */
+	class LoadOperationException extends WrappedException {
+
+		private static final long serialVersionUID = 8499010336607816601L;
+
+		private final URI uri;
+
+		/**
+		 * Instantiates a new load operation exception.
+		 *
+		 * @param uri the uri of the resource that failed to load
+		 * @param exception the exception
+		 */
+		public LoadOperationException(URI uri, Throwable exception) {
+			this(uri, new Exception(exception));
+		}
+
+		/**
+		 * Instantiates a new load operation exception.
+		 *
+		 * @param uri the uri of the resource that failed to load
+		 * @param exception the exception
+		 */
+		public LoadOperationException(URI uri, Exception exception) {
+			super(exception);
+			this.uri = uri;
+		}
+
+		/**
+		 * Gets the URI of the resource that failed to load.
+		 *
+		 * @return the uri
+		 */
+		public URI getUri() {
+			return uri;
+		}
+
+	}
+
+}
diff --git a/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/ParallelResourceLoader.java b/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/ParallelResourceLoader.java
new file mode 100644
index 0000000..82dbd1b
--- a/dev/null
+++ b/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/ParallelResourceLoader.java
@@ -0,0 +1,172 @@
+/*******************************************************************************
+ * Copyright (c) 2011 Sigasi NV (http://www.sigasi.com) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *******************************************************************************/
+package org.eclipse.xtext.builder.resourceloader;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.NoSuchElementException;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.TimeUnit;
+
+import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.ecore.resource.Resource;
+import org.eclipse.emf.ecore.resource.ResourceSet;
+import org.eclipse.xtext.resource.XtextResourceSet;
+import org.eclipse.xtext.util.Triple;
+import org.eclipse.xtext.util.Tuples;
+
+import com.google.common.collect.Lists;
+import com.google.inject.Provider;
+
+/**
+ * Loads resources in one more separate threads.
+ *
+ * @author Lieven Lemiengre - Initial contribution and API
+ * @since 2.1
+ */
+public class ParallelResourceLoader extends AbstractResourceLoader {
+
+	private static final long MAX_WAIT_TIME = TimeUnit.SECONDS.toMillis(60);
+
+	private final int nThreads;
+	private final int queueSize;
+	private long timeout;
+
+	public ParallelResourceLoader(Provider<XtextResourceSet> resourceSetProvider, Sorter sorter, int nThreads, int queueSize) {
+		super(resourceSetProvider, sorter);
+		this.nThreads = nThreads;
+		this.queueSize = queueSize;
+		this.timeout = MAX_WAIT_TIME;
+	}
+
+	public long getTimeout() {
+		return timeout;
+	}
+
+	public void setTimeout(long time, TimeUnit unit) {
+		this.timeout = unit.toMillis(time);
+	}
+
+	public LoadOperation create(ResourceSet parent) {
+		return new CheckedLoadOperation(new ParallelLoadOperation(parent));
+	}
+
+	private class ParallelLoadOperation implements LoadOperation {
+
+		private final BlockingQueue<Triple<URI, Resource, Throwable>> resourceQueue;
+		private final ThreadLocal<ResourceSet> resourceSetProvider;
+		private final ExecutorService executor;
+		private final ResourceSet parent;
+		private final long waitTime;
+		private int toProcess;
+
+		public ParallelLoadOperation(final ResourceSet parent) {
+			this.parent = parent;
+			if(queueSize == 0) {
+				this.resourceQueue = new SynchronousQueue<Triple<URI, Resource, Throwable>>(true);
+			} else {
+				this.resourceQueue = new ArrayBlockingQueue<Triple<URI, Resource, Throwable>>(queueSize);
+			}
+			this.resourceSetProvider = new ThreadLocal<ResourceSet>() {
+				@Override
+				protected ResourceSet initialValue() {
+					XtextResourceSet resourceSet = getResourceSetProvider().get();
+					resourceSet.getLoadOptions().putAll(parent.getLoadOptions());
+					resourceSet.setURIConverter(parent.getURIConverter());
+					return resourceSet;
+				}
+			};
+			this.executor = Executors.newFixedThreadPool(nThreads);
+			this.waitTime = getTimeout();
+		}
+
+		private class ResourceLoadJob implements Runnable {
+			private final URI uri;
+
+			public ResourceLoadJob(URI uri) {
+				this.uri = uri;
+			}
+
+			public void run() {
+				Throwable exception = null;
+				Resource resource = null;
+
+				// load resource
+				try {
+					ResourceSet localResourceSet = resourceSetProvider.get();
+					resource = loadResource(uri, localResourceSet, parent);
+					localResourceSet.getResources().clear();
+				} catch (Throwable t) {
+					exception = t;
+				}
+
+				// push resource to the queue, wait if queue is full
+				try {
+					resourceQueue.put(Tuples.create(uri, resource, exception));
+				} catch (InterruptedException e) {
+					Thread.currentThread().interrupt();
+				}
+			}
+		}
+
+		public Resource next() {
+			if (!hasNext())
+				throw new NoSuchElementException("The resource queue is empty or the execution was cancelled.");
+			Triple<URI, Resource, Throwable> result = null;
+			try {
+				result = resourceQueue.poll(waitTime, TimeUnit.MILLISECONDS);
+				toProcess--;
+			} catch (InterruptedException e) {
+				Thread.currentThread().interrupt();
+			}
+			if (result == null) {
+				throw new NullPointerException("Resource load job didn't return a result");
+			}
+
+			URI uri = result.getFirst();
+			Resource resource = result.getSecond();
+			Throwable throwable = result.getThird();
+
+			if (throwable != null) { // rethrow errors in the main thread
+				throw new LoadOperationException(uri, throwable);
+			}
+			return resource;
+		}
+
+		public boolean hasNext() {
+			return toProcess > 0;
+		}
+
+		public void load(Collection<URI> uris) {
+			toProcess += uris.size();
+			Collection<URI> workload = getSorter().sort(uris);
+			for(URI uri : workload) {
+				executor.execute(new ResourceLoadJob(uri));
+			}
+			executor.shutdown();
+		}
+
+		public Collection<URI> cancel() {
+			toProcess = 0;
+			List<Runnable> jobs = executor.shutdownNow();
+			List<URI> ret = Lists.newArrayList();
+			for (Runnable job : jobs) {
+				if (job instanceof ResourceLoadJob) {
+					ret.add(((ResourceLoadJob) job).uri);
+				}
+			}
+			return ret;
+		}
+
+	}
+
+}
diff --git a/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/ResourceLoaderProviders.java b/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/ResourceLoaderProviders.java
new file mode 100644
index 0000000..5e360c1
--- a/dev/null
+++ b/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/ResourceLoaderProviders.java
@@ -0,0 +1,67 @@
+/*******************************************************************************
+ * Copyright (c) 2011 Sigasi NV (http://www.sigasi.com) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *******************************************************************************/
+package org.eclipse.xtext.builder.resourceloader;
+
+import org.eclipse.xtext.builder.resourceloader.IResourceLoader.Sorter;
+import org.eclipse.xtext.resource.XtextResourceSet;
+
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+
+/**
+ * @author Lieven Lemiengre - Initial contribution and API
+ * @since 2.1
+ */
+public final class ResourceLoaderProviders {
+
+	public static abstract class AbstractResourceLoaderProvider implements Provider<IResourceLoader> {
+
+		@Inject
+		private Provider<XtextResourceSet> resourceSetProvider;
+
+		@Inject
+		private Sorter resourceSorter;
+
+		public Provider<XtextResourceSet> getResourceSetProvider() {
+			return resourceSetProvider;
+		}
+
+		public Sorter getResourceSorter() {
+			return resourceSorter;
+		}
+	}
+
+	/** Returns a loader with a parallelization degree of 2 to 4 (depending on how many processors are available). */
+	public static Provider<IResourceLoader> getParallelLoader() {
+		int nProcessors = Runtime.getRuntime().availableProcessors();
+		int nThreads = Math.max(2, Math.min(4, nProcessors));
+		return getParallelLoader(nThreads, 0);
+	}
+
+	public static Provider<IResourceLoader> getParallelLoader(final int nrOfThreads) {
+		return getParallelLoader(nrOfThreads, 0);
+	}
+
+	public static Provider<IResourceLoader> getParallelLoader(final int nrOfThreads, final int bufferSize) {
+		return new AbstractResourceLoaderProvider() {
+			public IResourceLoader get() {
+				ParallelResourceLoader resourceLoader = new ParallelResourceLoader(getResourceSetProvider(), getResourceSorter(), nrOfThreads, bufferSize);
+				return resourceLoader;
+			}
+		};
+	}
+
+	public static Provider<IResourceLoader> getSerialLoader() {
+		return new AbstractResourceLoaderProvider() {
+			public IResourceLoader get() {
+				return new SerialResourceLoader(getResourceSetProvider(), getResourceSorter());
+			}
+		};
+	}
+
+}
diff --git a/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/SerialResourceLoader.java b/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/SerialResourceLoader.java
new file mode 100644
index 0000000..3765b68
--- a/dev/null
+++ b/plugins/org.eclipse.xtext.builder/src/org/eclipse/xtext/builder/resourceloader/SerialResourceLoader.java
@@ -0,0 +1,58 @@
+/*******************************************************************************
+ * Copyright (c) 2011 Sigasi NV (http://www.sigasi.com) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *******************************************************************************/
+package org.eclipse.xtext.builder.resourceloader;
+
+import java.util.Collection;
+import java.util.Queue;
+
+import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.ecore.resource.Resource;
+import org.eclipse.emf.ecore.resource.ResourceSet;
+import org.eclipse.xtext.resource.XtextResourceSet;
+
+import com.google.common.collect.Lists;
+import com.google.inject.Provider;
+
+/**
+ * Loads resources in sequentially in the same thread as it was invoked.
+ *
+ * @author Lieven Lemiengre - Initial contribution and API
+ * @since 2.1
+ */
+public class SerialResourceLoader extends AbstractResourceLoader {
+
+	public SerialResourceLoader(Provider<XtextResourceSet> resourceSetProvider, Sorter sorter) {
+		super(resourceSetProvider, sorter);
+	}
+
+	public LoadOperation create(final ResourceSet parent) {
+		final Queue<URI> queue = Lists.newLinkedList();
+
+		return new CheckedLoadOperation(new LoadOperation() {
+
+			public Resource next() {
+				URI uri = queue.poll();
+				Resource resource = parent.getResource(uri, true);
+				return resource;
+			}
+
+			public boolean hasNext() {
+				return !queue.isEmpty();
+			}
+
+			public Collection<URI> cancel() {
+				return queue;
+			}
+
+			public void load(Collection<URI> uris) {
+				queue.addAll(getSorter().sort(uris));
+			}
+		});
+	}
+
+}
diff --git a/plugins/org.eclipse.xtext.ui.shared/src/org/eclipse/xtext/ui/shared/internal/SharedModule.java b/plugins/org.eclipse.xtext.ui.shared/src/org/eclipse/xtext/ui/shared/internal/SharedModule.java
index 8c1f1c8..cf714f1 100644
--- a/plugins/org.eclipse.xtext.ui.shared/src/org/eclipse/xtext/ui/shared/internal/SharedModule.java
+++ b/plugins/org.eclipse.xtext.ui.shared/src/org/eclipse/xtext/ui/shared/internal/SharedModule.java
@@ -20,6 +20,8 @@ import org.eclipse.xtext.builder.clustering.ClusteringBuilderState;
 import org.eclipse.xtext.builder.impl.DirtyStateAwareResourceDescriptions;
 import org.eclipse.xtext.builder.impl.ProjectOpenedOrClosedListener;
 import org.eclipse.xtext.builder.impl.XtextBuilder;
+import org.eclipse.xtext.builder.resourceloader.IResourceLoader;
+import org.eclipse.xtext.builder.resourceloader.ResourceLoaderProviders;
 import org.eclipse.xtext.resource.IExternalContentSupport;
 import org.eclipse.xtext.resource.IResourceDescriptions;
 import org.eclipse.xtext.resource.IResourceServiceProvider;
@@ -29,8 +31,8 @@ import org.eclipse.xtext.ui.notification.IStateChangeEventBroker;
 import org.eclipse.xtext.ui.notification.StateChangeEventBroker;
 import org.eclipse.xtext.ui.resource.IResourceSetProvider;
 import org.eclipse.xtext.ui.resource.IStorage2UriMapper;
-import org.eclipse.xtext.ui.resource.Storage2UriMapperImpl;
 import org.eclipse.xtext.ui.resource.SimpleResourceSetProvider;
+import org.eclipse.xtext.ui.resource.Storage2UriMapperImpl;
 import org.eclipse.xtext.ui.shared.JdtHelper;
 import org.eclipse.xtext.ui.util.IJdtHelper;
 
@@ -43,7 +45,7 @@ import com.google.inject.name.Names;
  * @author Sven Efftinge - Initial contribution and API
  */
 public class SharedModule extends AbstractModule {
-	
+
 	@Override
 	protected void configure() {
 		bind(IBuilderState.class).to(ClusteringBuilderState.class).in(Scopes.SINGLETON);
@@ -52,14 +54,14 @@ public class SharedModule extends AbstractModule {
 		bind(IResourceSetProvider.class).to(SimpleResourceSetProvider.class);
 		bind(IExtensionRegistry.class).toInstance(Platform.getExtensionRegistry());
 		bind(IResourceChangeListener.class).annotatedWith(Names.named(ProjectOpenedOrClosedListener.class.getName())).to(ProjectOpenedOrClosedListener.class);
-		
+
 		bind(IExternalContentSupport.IExternalContentProvider.class).to(IDirtyStateManager.class).in(Scopes.SINGLETON);
 		bind(IDirtyStateManager.class).to(DirtyStateManager.class).in(Scopes.SINGLETON);
 		bind(IStateChangeEventBroker.class).to(StateChangeEventBroker.class).in(Scopes.SINGLETON);
 
 		bind(IncrementalProjectBuilder.class).to(XtextBuilder.class);
 		bind(IStorage2UriMapper.class).to(Storage2UriMapperImpl.class).in(Scopes.SINGLETON);
-		
+
 		bind(IWorkbench.class).toProvider(new Provider<IWorkbench>() {
 			public IWorkbench get() {
 				if (PlatformUI.isWorkbenchRunning())
@@ -67,14 +69,35 @@ public class SharedModule extends AbstractModule {
 				return null;
 			}
 		});
-		
+
 		bind(IWorkspace.class).toProvider(new Provider<IWorkspace>() {
 			public IWorkspace get() {
 				return ResourcesPlugin.getWorkspace();
 			}
 		});
-		
+
 		bind(IJdtHelper.class).to(JdtHelper.class).asEagerSingleton();
+
+		boolean parallel = true;
+		if (parallel) {
+			bind(IResourceLoader.class).toProvider(ResourceLoaderProviders.getParallelLoader());
+
+			bind(IResourceLoader.class).annotatedWith(
+					Names.named(ClusteringBuilderState.RESOURCELOADER_GLOBAL_INDEX)).toProvider(
+					ResourceLoaderProviders.getParallelLoader());
+
+			bind(IResourceLoader.class).annotatedWith(Names.named(ClusteringBuilderState.RESOURCELOADER_CROSS_LINKING))
+					.toProvider(ResourceLoaderProviders.getParallelLoader());
+		} else {
+			bind(IResourceLoader.class).toProvider(ResourceLoaderProviders.getSerialLoader());
+
+			bind(IResourceLoader.class).annotatedWith(
+					Names.named(ClusteringBuilderState.RESOURCELOADER_GLOBAL_INDEX)).toProvider(
+					ResourceLoaderProviders.getSerialLoader());
+
+			bind(IResourceLoader.class).annotatedWith(Names.named(ClusteringBuilderState.RESOURCELOADER_CROSS_LINKING))
+					.toProvider(ResourceLoaderProviders.getSerialLoader());
+		}
 	}
-	
+
 }
diff --git a/tests/org.eclipse.xtext.builder.tests/src/org/eclipse/xtext/builder/builderState/Bug349445Test.java b/tests/org.eclipse.xtext.builder.tests/src/org/eclipse/xtext/builder/builderState/Bug349445Test.java
index 42767c5..7c4a539 100644
--- a/tests/org.eclipse.xtext.builder.tests/src/org/eclipse/xtext/builder/builderState/Bug349445Test.java
+++ b/tests/org.eclipse.xtext.builder.tests/src/org/eclipse/xtext/builder/builderState/Bug349445Test.java
@@ -10,6 +10,8 @@ package org.eclipse.xtext.builder.builderState;
 import java.util.Collections;
 import java.util.Map;
 
+import junit.framework.TestCase;
+
 import org.eclipse.core.runtime.IProgressMonitor;
 import org.eclipse.emf.common.util.URI;
 import org.eclipse.emf.ecore.EcorePackage;
@@ -20,19 +22,20 @@ import org.eclipse.xtext.builder.impl.QueuedBuildData;
 import org.eclipse.xtext.builder.impl.ToBeBuilt;
 import org.eclipse.xtext.naming.QualifiedName;
 import org.eclipse.xtext.resource.IResourceDescription;
-import org.eclipse.xtext.resource.IResourceServiceProvider;
 import org.eclipse.xtext.resource.IResourceDescription.Delta;
+import org.eclipse.xtext.resource.IResourceServiceProvider;
+import org.eclipse.xtext.ui.shared.internal.SharedModule;
+import org.eclipse.xtext.util.Modules2;
 
 import com.google.common.collect.ImmutableList;
 import com.google.inject.AbstractModule;
 import com.google.inject.Guice;
 import com.google.inject.Injector;
 
-import junit.framework.TestCase;
-
 /**
  * @author Sebastian Zarnekow - Initial contribution and API
  */
+@SuppressWarnings("restriction")
 public class Bug349445Test extends TestCase implements PersistedStateProvider, IMarkerUpdater, IResourceServiceProvider.Registry {
 
 	private IBuilderState testMe;
@@ -40,14 +43,14 @@ public class Bug349445Test extends TestCase implements PersistedStateProvider, I
 
 	@Override
 	protected void setUp() throws Exception {
-		Injector injector = Guice.createInjector(new AbstractModule() {
+		Injector injector = Guice.createInjector(Modules2.mixin(new SharedModule(), new AbstractModule() {
 			@Override
 			protected void configure() {
 				bind(PersistedStateProvider.class).toInstance(Bug349445Test.this);
 				bind(IMarkerUpdater.class).toInstance(Bug349445Test.this);
 				bind(IResourceServiceProvider.Registry.class).toInstance(Bug349445Test.this);
 			}
-		});
+		}));
 		loadCalled = 0;
 		testMe = injector.getInstance(ClusteringBuilderState.class);
 	}
diff --git a/tests/org.eclipse.xtext.builder.tests/src/org/eclipse/xtext/builder/builderState/PersistableResourceDescriptionsTest.java b/tests/org.eclipse.xtext.builder.tests/src/org/eclipse/xtext/builder/builderState/PersistableResourceDescriptionsTest.java
index b1dfe5d..52e5c94 100644
--- a/tests/org.eclipse.xtext.builder.tests/src/org/eclipse/xtext/builder/builderState/PersistableResourceDescriptionsTest.java
+++ b/tests/org.eclipse.xtext.builder.tests/src/org/eclipse/xtext/builder/builderState/PersistableResourceDescriptionsTest.java
@@ -30,7 +30,7 @@ import org.eclipse.xtext.resource.IResourceDescription;
 import org.eclipse.xtext.resource.IResourceDescription.Delta;
 import org.eclipse.xtext.resource.containers.DelegatingIAllContainerAdapter;
 import org.eclipse.xtext.resource.containers.IAllContainersState;
-import org.eclipse.xtext.ui.shared.SharedStateModule;
+import org.eclipse.xtext.ui.shared.internal.SharedModule;
 import org.eclipse.xtext.util.StringInputStream;
 
 import com.google.common.base.Function;
@@ -44,6 +44,7 @@ import com.google.inject.Injector;
 /**
  * @author Sven Efftinge - Initial contribution and API
  */
+@SuppressWarnings("restriction")
 public class PersistableResourceDescriptionsTest extends AbstractXtextTests {
 	private static final String FILE_EXT = ".buildertestlanguage";
 	private Injector builderInjector;
@@ -56,7 +57,7 @@ public class PersistableResourceDescriptionsTest extends AbstractXtextTests {
 	public void setUp() throws Exception {
 		super.setUp();
 		with(new BuilderTestLanguageStandaloneSetup());
-		SharedStateModule module = new SharedStateModule();
+		SharedModule module = new SharedModule();
 		builderInjector = Guice.createInjector(module);
 		builderState = builderInjector.getInstance(ClusteringBuilderState.class);
 		uriConverter = new ExtensibleURIConverterImpl() {