Maintain only two worker processes per CPU core instead of three. This should reduce memory consumption.

src/calibre/gui2/add.py

@@ -1,7 +1,7 @@
 '''
 UI for adding books to the database and saving books to disk
 '''
-import os
+import os, shutil
 from Queue import Queue, Empty
 
 from PyQt4.Qt import QThread, SIGNAL, QObject, QTimer, Qt
@@ -167,6 +167,15 @@ class Adder(QObject):
                 self.add_formats(id, formats)
                 self.number_of_books_added += 1
 
+    def cleanup(self):
+        if hasattr(self, 'worker') and hasattr(self.worker, 'tdir') and \
+                self.worker.tdir is not None:
+            if os.path.exists(self.worker.tdir):
+                try:
+                    shutil.rmtree(self.worker.tdir)
+                except:
+                    pass
+
 class Saver(QObject):
 
     def __init__(self, parent, db, callback, rows, path,

src/calibre/gui2/main.py

@@ -427,6 +427,7 @@ class Main(MainWindow, Ui_MainWindow, DeviceGUI):
                             os.path.expanduser('~')))
             if not dir:
                 QCoreApplication.exit(1)
+                raise SystemExit(1)
             else:
                 self.library_path = dir
                 db = LibraryDatabase2(self.library_path)
@@ -522,6 +523,11 @@ class Main(MainWindow, Ui_MainWindow, DeviceGUI):
 
     @property
     def spare_server(self):
+        # Because of the use of the property decorator, we're called one
+        # extra time. Ignore.
+        if not hasattr(self, '__spare_server_property_limiter'):
+            self.__spare_server_property_limiter = True
+            return None
         try:
             QTimer.singleShot(1000, self.add_spare_server)
             return self.spare_servers.pop()
@@ -872,6 +878,7 @@ class Main(MainWindow, Ui_MainWindow, DeviceGUI):
                     _('Failed to read metadata from the following')+':',
                     det_msg='\n\n'.join(det_msg), show=True)
 
+        self._adder.cleanup()
         self._adder = None