Index: kdevplatform/interfaces/iprojectcontroller.h
===================================================================
--- kdevplatform/interfaces/iprojectcontroller.h
+++ kdevplatform/interfaces/iprojectcontroller.h
@@ -117,6 +117,11 @@
      */
     static bool parseAllProjectSources();
 
+    /**
+     * @returns whether project directories should be monitored for changes or not
+     */
+    virtual bool watchAllProjectDirectories();
+
 public Q_SLOTS:
     /**
      * Tries finding a project-file for the given source-url and opens it.
Index: kdevplatform/interfaces/iprojectcontroller.cpp
===================================================================
--- kdevplatform/interfaces/iprojectcontroller.cpp
+++ kdevplatform/interfaces/iprojectcontroller.cpp
@@ -42,5 +42,12 @@
     return group.readEntry( "Parse All Project Sources", true );    
 }
 
+bool IProjectController::watchAllProjectDirectories()
+{
+    KConfigGroup group = ICore::self()->activeSession()->config()->group( "Project Manager" );
+    return group.readEntry( "Monitor All Project Directories", true );
+}
+
+
 }
 
Index: kdevplatform/project/CMakeLists.txt
===================================================================
--- kdevplatform/project/CMakeLists.txt
+++ kdevplatform/project/CMakeLists.txt
@@ -15,6 +15,7 @@
     abstractfilemanagerplugin.cpp
     filemanagerlistjob.cpp
     projectfiltermanager.cpp
+    projectwatcher.cpp
     interfaces/iprojectbuilder.cpp
     interfaces/iprojectfilemanager.cpp
     interfaces/ibuildsystemmanager.cpp
Index: kdevplatform/project/abstractfilemanagerplugin.h
===================================================================
--- kdevplatform/project/abstractfilemanagerplugin.h
+++ kdevplatform/project/abstractfilemanagerplugin.h
@@ -35,6 +35,8 @@
 
 class AbstractFileManagerPluginPrivate;
 
+class ProjectWatcher;
+
 /**
  * This class can be used as a common base for file managers.
  *
Index: kdevplatform/project/abstractfilemanagerplugin.cpp
===================================================================
--- kdevplatform/project/abstractfilemanagerplugin.cpp
+++ kdevplatform/project/abstractfilemanagerplugin.cpp
@@ -27,6 +27,7 @@
 #include <QHashIterator>
 #include <QFileInfo>
 #include <QApplication>
+#include <QElapsedTimer>
 
 #include <KMessageBox>
 #include <KLocalizedString>
@@ -38,6 +39,7 @@
 #include <serialization/indexedstring.h>
 
 #include "projectfiltermanager.h"
+#include "projectwatcher.h"
 #include "debug.h"
 
 #define ifDebug(x)
@@ -86,7 +88,7 @@
                      const KIO::UDSEntryList& entries);
 
     void deleted(const QString &path);
-    void created(const QString &path);
+    void dirty(const QString &path);
 
     void projectClosing(IProject* project);
     void jobFinished(KJob* job);
@@ -100,7 +102,7 @@
 
     void removeFolder(ProjectFolderItem* folder);
 
-    QHash<IProject*, KDirWatch*> m_watchers;
+    QHash<IProject*, ProjectWatcher*> m_watchers;
     QHash<IProject*, QList<FileManagerListJob*> > m_projectJobs;
     QVector<QString> m_stoppedFolders;
     ProjectFilterManager m_filters;
@@ -117,13 +119,32 @@
         }
         m_projectJobs.remove(project);
     }
-    delete m_watchers.take(project);
+    QElapsedTimer timer;
+    if (m_watchers.contains(project)) {
+        timer.start();
+    }
+    ProjectWatcher* watcher = m_watchers.value(project, nullptr);
+    int nWatched = 0;
+    if (watcher) {
+        nWatched = watcher->size();
+        delete watcher;
+        m_watchers.remove(project);
+    }
+    if (timer.isValid()) {
+        qCInfo(FILEMANAGER) << "Deleting" << nWatched << "entry dir watcher took" << timer.elapsed() / 1000.0 << "seconds for project" << project->name();
+    }
     m_filters.remove(project);
 }
 
 KIO::Job* AbstractFileManagerPluginPrivate::eventuallyReadFolder(ProjectFolderItem* item)
 {
-    FileManagerListJob* listJob = new FileManagerListJob( item );
+    ProjectWatcher* watcher;
+    if (ICore::self()->projectController()->watchAllProjectDirectories() && m_watchers.contains(item->project())) {
+        watcher = m_watchers[item->project()];
+    } else {
+        watcher = nullptr;
+    }
+    FileManagerListJob* listJob = new FileManagerListJob( item, watcher );
     m_projectJobs[ item->project() ] << listJob;
     qCDebug(FILEMANAGER) << "adding job" << listJob << item << item->path() << "for project" << item->project();
 
@@ -247,17 +268,17 @@
     }
 }
 
-void AbstractFileManagerPluginPrivate::created(const QString& path_)
+void AbstractFileManagerPluginPrivate::dirty(const QString& path_)
 {
-    qCDebug(FILEMANAGER) << "created:" << path_;
+    qCDebug(FILEMANAGER) << "dirty:" << path_;
     QFileInfo info(path_);
 
     ///FIXME: share memory with parent
     const Path path(path_);
     const IndexedString indexedPath(path.pathOrUrl());
     const IndexedString indexedParent(path.parent().pathOrUrl());
 
-    QHashIterator<IProject*, KDirWatch*> it(m_watchers);
+    QHashIterator<IProject*, ProjectWatcher*> it(m_watchers);
     while (it.hasNext()) {
         const auto p = it.next().key();
         if ( !p->projectItem()->model() ) {
@@ -285,21 +306,6 @@
             // also gets triggered for kate's backup files
             continue;
         }
-        foreach ( ProjectFolderItem* parentItem, p->foldersForPath(indexedParent) ) {
-            if ( info.isDir() ) {
-                ProjectFolderItem* folder = q->createFolderItem( p, path, parentItem );
-                if (folder) {
-                    emit q->folderAdded( folder );
-                    auto job = eventuallyReadFolder( folder );
-                    job->start();
-                }
-            } else {
-                ProjectFileItem* file = q->createFileItem( p, path, parentItem );
-                if (file) {
-                    emit q->fileAdded( file );
-                }
-            }
-        }
     }
 }
 
@@ -320,7 +326,7 @@
     const Path path(QUrl::fromLocalFile(path_));
     const IndexedString indexed(path.pathOrUrl());
 
-    QHashIterator<IProject*, KDirWatch*> it(m_watchers);
+    QHashIterator<IProject*, ProjectWatcher*> it(m_watchers);
     while (it.hasNext()) {
         const auto p = it.next().key();
         if (path == p->path()) {
@@ -388,20 +394,31 @@
     if ( !folder->path().isLocalFile() ) {
         return;
     }
-    Q_ASSERT(m_watchers.contains(folder->project()));
     const QString path = folder->path().toLocalFile();
-    m_watchers[folder->project()]->stopDirScan(path);
+    ProjectWatcher* watcher = m_watchers.value(folder->project(), nullptr);
+    if (watcher && watcher->contains(path)) {
+        m_watchers[folder->project()]->stopDirScan(path);
+    }
     m_stoppedFolders.append(path);
 }
 
 void AbstractFileManagerPluginPrivate::continueWatcher(ProjectFolderItem* folder)
 {
     if ( !folder->path().isLocalFile() ) {
         return;
     }
-    Q_ASSERT(m_watchers.contains(folder->project()));
     const QString path = folder->path().toLocalFile();
-    m_watchers[folder->project()]->restartDirScan(path);
+    if (ICore::self()->projectController()->watchAllProjectDirectories()) {
+        // restart the watcher on if @p folder corresponds to a directory
+        // and the project is being monitored. Add the directory if not
+        // being watched already.
+        if (m_watchers.contains(folder->project()) && QFileInfo(path).isDir()) {
+            if (!m_watchers[folder->project()]->restartDirScan(path)) {
+                // path wasn't being watched yet
+                m_watchers[folder->project()]->addDir(path);
+            }
+        }
+    }
     const int idx = m_stoppedFolders.indexOf(path);
     if (idx != -1) {
         m_stoppedFolders.remove(idx);
@@ -431,6 +448,10 @@
             job->removeSubDir(folder);
         }
     }
+    ProjectWatcher* watcher = m_watchers.value(folder->project(), nullptr);
+    if (watcher) {
+        watcher->removeDir(folder->path().toLocalFile());
+    }
     folder->parent()->removeRow( folder->row() );
 }
 
@@ -472,14 +493,13 @@
 
     ///TODO: check if this works for remote files when something gets changed through another KDE app
     if ( project->path().isLocalFile() ) {
-        d->m_watchers[project] = new KDirWatch( project );
+        d->m_watchers[project] = new ProjectWatcher(project);
 
-        connect(d->m_watchers[project], &KDirWatch::created,
-                this, [&] (const QString& path_) { d->created(path_); });
+        // set up the signal handling; feeding the dirwatcher is handled elsewhere.
+        connect(d->m_watchers[project], &KDirWatch::dirty,
+                this, [&] (const QString& path_) { d->dirty(path_); });
         connect(d->m_watchers[project], &KDirWatch::deleted,
                 this, [&] (const QString& path_) { d->deleted(path_); });
-
-        d->m_watchers[project]->addDir(project->path().toLocalFile(), KDirWatch::WatchSubDirs | KDirWatch:: WatchFiles );
     }
 
     d->m_filters.add(project);
Index: kdevplatform/project/filemanagerlistjob.h
===================================================================
--- kdevplatform/project/filemanagerlistjob.h
+++ kdevplatform/project/filemanagerlistjob.h
@@ -22,6 +22,7 @@
 
 #include <KIO/Job>
 #include <QQueue>
+#include <QSet>
 
 // uncomment to time imort jobs
 // #define TIME_IMPORT_JOB
@@ -33,13 +34,14 @@
 namespace KDevelop
 {
     class ProjectFolderItem;
+    class ProjectWatcher;
 
 class FileManagerListJob : public KIO::Job
 {
     Q_OBJECT
 
 public:
-    explicit FileManagerListJob(ProjectFolderItem* item);
+    explicit FileManagerListJob(ProjectFolderItem* item, ProjectWatcher* watcher = nullptr);
     ProjectFolderItem* item() const;
 
     void addSubDir(ProjectFolderItem* item);
@@ -73,6 +75,9 @@
     QElapsedTimer m_subTimer;
     qint64 m_subWaited = 0;
 #endif
+    void maybeWatch(const QString& path);
+    // local copy of the project's dirwatcher
+    ProjectWatcher* m_watcher;
 };
 
 }
Index: kdevplatform/project/filemanagerlistjob.cpp
===================================================================
--- kdevplatform/project/filemanagerlistjob.cpp
+++ kdevplatform/project/filemanagerlistjob.cpp
@@ -18,6 +18,7 @@
 */
 
 #include "filemanagerlistjob.h"
+#include "projectwatcher.h"
 
 #include <interfaces/iproject.h>
 #include <project/projectmodel.h>
@@ -28,14 +29,17 @@
 #include <QtConcurrentRun>
 #include <QDir>
 
+#include <KDirWatch>
+
 using namespace KDevelop;
 
-FileManagerListJob::FileManagerListJob(ProjectFolderItem* item)
-    : KIO::Job(), m_item(item), m_aborted(false)
+FileManagerListJob::FileManagerListJob(ProjectFolderItem* item, ProjectWatcher* watcher)
+    : KIO::Job(), m_item(item), m_aborted(false), m_watcher(watcher)
 {
     qRegisterMetaType<KIO::UDSEntryList>("KIO::UDSEntryList");
     qRegisterMetaType<KIO::Job*>();
     qRegisterMetaType<KJob*>();
+    setObjectName(QStringLiteral("FileManager list job for project") + item->project()->name());
 
     /* the following line is not an error in judgment, apparently starting a
      * listJob while the previous one hasn't self-destructed takes a lot of time,
@@ -73,6 +77,13 @@
     entryList.append(entriesIn);
 }
 
+void FileManagerListJob::maybeWatch(const QString& path)
+{
+    if (m_watcher) {
+        m_watcher->addDir(path);
+    }
+}
+
 void FileManagerListJob::startNextJob()
 {
     if ( m_listQueue.isEmpty() || m_aborted ) {
@@ -95,12 +106,14 @@
             if (m_aborted) {
                 return;
             }
+            maybeWatch(path.toLocalFile());
             KIO::UDSEntryList results;
-            std::transform(entries.begin(), entries.end(), std::back_inserter(results), [] (const QFileInfo& info) -> KIO::UDSEntry {
+            std::transform(entries.begin(), entries.end(), std::back_inserter(results), [this] (const QFileInfo& info) -> KIO::UDSEntry {
                 KIO::UDSEntry entry;
                 entry.insert(KIO::UDSEntry::UDS_NAME, info.fileName());
                 if (info.isDir()) {
                     entry.insert(KIO::UDSEntry::UDS_FILE_TYPE, QT_STAT_DIR);
+                    maybeWatch(info.absoluteFilePath());
                 }
                 if (info.isSymLink()) {
                     entry.insert(KIO::UDSEntry::UDS_LINK_DEST, info.symLinkTarget());
Index: kdevplatform/shell/settings/projectconfig.kcfg
===================================================================
--- kdevplatform/shell/settings/projectconfig.kcfg
+++ kdevplatform/shell/settings/projectconfig.kcfg
@@ -23,5 +23,10 @@
         <label>Save all open documents before building anything</label>
         <whatsthis>If this option is set all open documents will be automatically saved before any build is started.</whatsthis>
     </entry>
+    <entry name="watchAllProjectDirectories" key="Monitor All Project Directories" type="Bool" default="true">
+        <default>true</default>
+        <label>Monitor all directories of a project for changes</label>
+        <whatsthis>If this option is set, KDevelop will monitor all project directories for changes. This keeps the overview in the Projects toolview in sync with the directory on disk. It can also really slow down the import of very big projects and consume considerable resources.</whatsthis>
+    </entry>
   </group>
 </kcfg>
Index: kdevplatform/shell/settings/projectpreferences.ui
===================================================================
--- kdevplatform/shell/settings/projectpreferences.ui
+++ kdevplatform/shell/settings/projectpreferences.ui
@@ -62,6 +62,16 @@
     </widget>
    </item>
    <item>
+    <widget class="QCheckBox" name="kcfg_watchAllProjectDirectories">
+     <property name="toolTip">
+      <string>Monitor all directories of a project for changes.</string>
+     </property>
+     <property name="text">
+      <string>Monitor all project directories for changes</string>
+     </property>
+    </widget>
+   </item>
+   <item>
     <spacer name="verticalSpacer">
      <property name="orientation">
       <enum>Qt::Vertical</enum>