diff -r 59d630fe8661 masterfs/apichanges.xml
--- a/masterfs/apichanges.xml	Mon Nov 19 12:07:47 2012 +0100
+++ b/masterfs/apichanges.xml	Tue Nov 20 11:59:03 2012 +0100
@@ -49,6 +49,22 @@
         <apidef name="masterfs">MasterFileSystem API</apidef>
     </apidefs>
     <changes>
+        <change id="org.netbeans.io.suspend">
+            <api name="masterfs"/>
+            <summary>A property to suspend native listeners</summary>
+            <version major="2" minor="42"/>
+            <date day="22" month="11" year="2012"/>
+            <author login="jtulach"/>
+            <compatibility addition="yes" binary="compatible" 
+                source="compatible" semantic="compatible" 
+                deprecation="no" deletion="no" modification="no"
+            />
+            <description>
+                A <a href="architecture-summary.html#systemproperty-org.netbeans.io.suspend">
+                way</a> to temporarily suspend native listeners.
+            </description>
+            <issue number="222193"/>
+        </change>
         <change id="fileLocked.io.exception">
             <api name="masterfs"/>
             <summary>fileLocked method can throw <code>IOException</code></summary>
diff -r 59d630fe8661 masterfs/arch.xml
--- a/masterfs/arch.xml	Mon Nov 19 12:07:47 2012 +0100
+++ b/masterfs/arch.xml	Tue Nov 20 11:59:03 2012 +0100
@@ -533,6 +533,36 @@
     consumption, not for consumption by other parts of the system. The name and
     meaning of this property may change in any release.
     </api>
+    
+    <api name="org.netbeans.io.suspend" category="devel" group="systemproperty" type="export">
+        <p>
+    Native listeners check the <code>org.netbeans.io.suspend</code> property. 
+    If it is set to integer greater than zero, they stop delivering file change events.
+    The list of modified directories is recorded (its size is made available
+    by setting its string value into <code>org.netbeans.io.pending</code> property), 
+    but its processing is suspended. Events are delivered when 
+    <code>org.netbeans.io.suspend</code> property changes its value to <code>0</code>
+    or becomes empty.
+    </p>
+    <p>
+    I/O intensive operations in other NetBeans modules are advised
+    to honour the <code>org.netbeans.io.suspend</code> property as well and
+    suspend their I/O activities too.
+    </p>
+    <p>
+    In order to properly communicate changes to the property between multiple
+    <em>receivers</em> and multiple <em>controllers</em> it is suggested to
+    only manipulate the value under <code>synchronized("org.netbeans.io.suspend".intern())</code>
+    lock. Those changing the value are supposed to increment it by one when they
+    request the suspend and decrement it by one when they want to resume their
+    own suspend.
+    </p>
+    <p>
+    Whenever a change to the state of the property is made,
+    <em>controllers</em> are supposed to 
+    <code>"org.netbeans.io.suspend".intern().notifyAll()</code>.
+    </p>
+    </api>
 </answer>
 
 
diff -r 59d630fe8661 masterfs/manifest.mf
--- a/masterfs/manifest.mf	Mon Nov 19 12:07:47 2012 +0100
+++ b/masterfs/manifest.mf	Tue Nov 20 11:59:03 2012 +0100
@@ -1,7 +1,7 @@
 Manifest-Version: 1.0
 OpenIDE-Module: org.netbeans.modules.masterfs/2
 OpenIDE-Module-Localizing-Bundle: org/netbeans/modules/masterfs/resources/Bundle.properties
-OpenIDE-Module-Specification-Version: 2.41
+OpenIDE-Module-Specification-Version: 2.42
 OpenIDE-Module-Recommends: org.netbeans.modules.masterfs.providers.Notifier
 OpenIDE-Module-Provides: org.openide.filesystems.FileUtil.toFileObject
 AutoUpdate-Show-In-Client: false
diff -r 59d630fe8661 masterfs/src/org/netbeans/modules/masterfs/watcher/Watcher.java
--- a/masterfs/src/org/netbeans/modules/masterfs/watcher/Watcher.java	Mon Nov 19 12:07:47 2012 +0100
+++ b/masterfs/src/org/netbeans/modules/masterfs/watcher/Watcher.java	Tue Nov 20 11:59:03 2012 +0100
@@ -57,9 +57,11 @@
 import org.netbeans.modules.masterfs.providers.ProvidedExtensions;
 import org.openide.filesystems.FileObject;
 import org.netbeans.modules.masterfs.providers.AnnotationProvider;
+import org.openide.util.Exceptions;
 import org.openide.util.Lookup;
 import org.openide.util.Lookup.Item;
 import org.openide.util.RequestProcessor;
+import org.openide.util.WeakSet;
 import org.openide.util.lookup.ServiceProvider;
 import org.openide.util.lookup.ServiceProviders;
 
@@ -354,7 +356,7 @@
         }
     }
 
-    private final Object lock = new Object();
+    private final Object lock = "org.netbeans.io.suspend".intern();
     private Set<FileObject> pending; // guarded by lock
     private static RequestProcessor RP = new RequestProcessor("Pending refresh", 1);
 
@@ -364,10 +366,25 @@
             Set<FileObject> toRefresh;
             synchronized(lock) {
                 toRefresh = pending;
-                pending = null;
                 if (toRefresh == null) {
                     return;
                 }
+                for (;;) {
+                    int cnt = Integer.getInteger("org.netbeans.io.suspend", 0); // NOI18N
+                    if (cnt <= 0) {
+                        break;
+                    }
+                    final String pndngSize = String.valueOf(toRefresh.size());
+                    System.setProperty("org.netbeans.io.pending", pndngSize); // NOI18N
+                    LOG.log(Level.FINE, "Suspend count {0} pending {1}", new Object[]{cnt, pndngSize});
+                    try {
+                        lock.wait(1500);
+                    } catch (InterruptedException ex) {
+                        LOG.log(Level.FINE, null, ex);
+                    }
+                }
+                System.getProperties().remove("org.netbeans.io.pending"); // NOI18N
+                pending = null;
             }
             LOG.log(Level.FINE, "Refreshing {0} directories", toRefresh.size());
 
@@ -391,7 +408,7 @@
         synchronized(lock) {
             if (pending == null) {
                 refreshTask.schedule(1500);
-                pending = new HashSet<FileObject>();
+                pending = new WeakSet<FileObject>();
             }
             pending.add(fo);
         }
@@ -404,7 +421,7 @@
         synchronized(lock) {
             if (pending == null) {
                 refreshTask.schedule(1500);
-                pending = new HashSet<FileObject>();
+                pending = new WeakSet<FileObject>();
             }
             pending.addAll(fos);
         }
diff -r 59d630fe8661 masterfs/test/unit/src/org/netbeans/modules/masterfs/watcher/WatcherSuspendTest.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/masterfs/test/unit/src/org/netbeans/modules/masterfs/watcher/WatcherSuspendTest.java	Tue Nov 20 11:59:03 2012 +0100
@@ -0,0 +1,193 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright 2011 Oracle and/or its affiliates. All rights reserved.
+ *
+ * Oracle and Java are registered trademarks of Oracle and/or its affiliates.
+ * Other names may be trademarks of their respective owners.
+ *
+ * The contents of this file are subject to the terms of either the GNU
+ * General Public License Version 2 only ("GPL") or the Common
+ * Development and Distribution License("CDDL") (collectively, the
+ * "License"). You may not use this file except in compliance with the
+ * License. You can obtain a copy of the License at
+ * http://www.netbeans.org/cddl-gplv2.html
+ * or nbbuild/licenses/CDDL-GPL-2-CP. See the License for the
+ * specific language governing permissions and limitations under the
+ * License.  When distributing the software, include this License Header
+ * Notice in each file and include the License file at
+ * nbbuild/licenses/CDDL-GPL-2-CP.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the GPL Version 2 section of the License file that
+ * accompanied this code. If applicable, add the following below the
+ * License Header, with the fields enclosed by brackets [] replaced by
+ * your own identifying information:
+ * "Portions Copyrighted [year] [name of copyright owner]"
+ *
+ * If you wish your version of this file to be governed by only the CDDL
+ * or only the GPL Version 2, indicate your decision by adding
+ * "[Contributor] elects to include this software in this distribution
+ * under the [CDDL or GPL Version 2] license." If you do not indicate a
+ * single choice of license, a recipient has the option to distribute
+ * your version of this file under either the CDDL, the GPL Version 2 or
+ * to extend the choice of license to its licensees as provided above.
+ * However, if you add GPL Version 2 code and therefore, elected the GPL
+ * Version 2 license, then the option applies only if the new code is
+ * made subject to such option by the copyright holder.
+ *
+ * Contributor(s):
+ *
+ * Portions Copyrighted 2011 Sun Microsystems, Inc.
+ */
+package org.netbeans.modules.masterfs.watcher;
+
+import java.io.File;
+import org.netbeans.modules.masterfs.providers.Notifier;
+import java.io.IOException;
+import java.lang.ref.Reference;
+import java.lang.ref.WeakReference;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.BlockingQueue;
+import org.netbeans.junit.MockServices;
+import org.netbeans.junit.NbTestCase;
+import org.netbeans.modules.masterfs.filebasedfs.fileobjects.FileObjectFactory;
+import org.netbeans.modules.masterfs.filebasedfs.naming.NamingFactory;
+import org.openide.filesystems.FileChangeAdapter;
+import org.openide.filesystems.FileEvent;
+import org.openide.filesystems.FileObject;
+import org.openide.filesystems.FileUtil;
+import org.openide.util.Lookup;
+
+/** Test the behavior of Watcher.
+ *
+ * @author Jaroslav Tulach <jtulach@netbeans.org>
+ */
+public class WatcherSuspendTest extends NbTestCase {
+    private TestNotifier notify;
+    private L listener;
+    private Watcher watcher;
+    
+    public WatcherSuspendTest(String s) {
+        super(s);
+    }
+
+    @Override
+    protected void setUp() throws Exception {
+        clearWorkDir();
+        MockServices.setServices(TestNotifier.class);
+        listener = new L();
+        watcher = Lookup.getDefault().lookup(Watcher.class);
+        notify = Lookup.getDefault().lookup(TestNotifier.class);
+        notify.start();
+    }
+
+    @Override
+    protected void tearDown() throws Exception {
+    }
+    
+    public void testSuspendRequests() throws Exception {
+        FileObject root = FileUtil.toFileObject(getWorkDir());
+        FileObject folder = root.createFolder("dir");
+        File dir = FileUtil.toFile(folder);
+        
+        FileObject[] arr = folder.getChildren();
+        folder.addFileChangeListener(listener);
+        assertEquals("Empty ", 0, arr.length);
+        
+        final String prop = "org.netbeans.io.suspend".intern();
+        synchronized (prop) {
+            int prev = Integer.getInteger(prop, 0);
+            System.setProperty(prop, "" + (prev + 1));
+            prop.notifyAll();
+        }
+        
+        new File(dir, "data.txt").createNewFile();
+        notify.event.offer(dir.getPath());
+        
+        assertProperty("One path waiting", "1", "org.netbeans.io.pending");
+        listener.assertEvents("No event yet", 0, 200);
+
+        synchronized (prop) {
+            int prev = Integer.getInteger(prop, 0);
+            System.setProperty(prop, "" + (prev - 1));
+            prop.notifyAll();
+        }
+        assertProperty("Pending status is cleared", null, "org.netbeans.io.pending");
+        
+        listener.assertEvents("One event delivered", 1, 5000);
+        
+        arr = folder.getChildren();
+        assertEquals("One child", 1, arr.length);
+        assertEquals("data.txt", arr[0].getNameExt());
+    }
+
+    private void assertProperty(String msg, String expVal, String propName) throws InterruptedException {
+        String val = null;
+        for (int i = 0; i < 100; i++) {
+            val = System.getProperty(propName);
+            if (expVal == null && val == null) {
+                return;
+            }
+            if (expVal != null && expVal.equals(val)) {
+                return;
+            }
+            Thread.sleep(100);
+        }
+        fail(msg + " exp: " + expVal + " was: " + val);
+    }
+
+    
+    private static final class L extends FileChangeAdapter {
+        private int cnt;
+
+        @Override
+        public synchronized void fileDataCreated(FileEvent fe) {
+            cnt++;
+        }
+
+        @Override
+        public void fileFolderCreated(FileEvent fe) {
+            cnt++;
+        }
+
+        private synchronized void assertEvents(
+            String msg, int cnt, int timeOut
+        ) throws InterruptedException {
+            if (this.cnt != cnt) {
+                wait(timeOut);
+            }
+            assertEquals(msg, cnt, this.cnt);
+        }
+        
+    }
+    
+    public static final class TestNotifier extends Notifier<Integer> {
+        final List<String> registered = new LinkedList<String>();
+        final BlockingQueue<String> event = new ArrayBlockingQueue<String>(10);
+
+        @Override
+        public Integer addWatch(String path) throws IOException {
+            int size = registered.size();
+            registered.add(path);
+            return size;
+        }
+
+        @Override
+        public void removeWatch(Integer key) throws IOException {
+            registered.set(key, null);
+        }
+
+        @Override
+        public String nextEvent() throws IOException, InterruptedException {
+            return event.take();
+        }
+
+        @Override
+        protected void start() throws IOException {
+            registered.clear();
+        }
+    }
+}