Allow to completely deactivate jedi type inference.

For slow systems or edge case.
It seem reasonable as uninstalling jedi may not be an option,
and completions without types is already good.

IPython/core/completer.py

@@ -86,7 +86,7 b' from IPython.utils import generics'
 from IPython.utils.dir2 import dir2, get_real_method
 from IPython.utils.process import arg_split
 from IPython.utils.py3compat import cast_unicode_py2
-from traitlets import Bool, Enum, observe
+from traitlets import Bool, Enum, observe, Int
 
 try:
     import jedi
@@ -475,6 +475,12 b' class Completer(Configurable):'
                     help="Experimental: Use Jedi to generate autocompletions. "
                     "Default to True if jedi is installed").tag(config=True)
 
+    jedi_compute_type_timeout = Int(default_value=400,
+        help="""Experimental: restrict time (in milliseconds) during which Jedi can compute types.
+        Set to 0 to stop computing types. Non-zero value lower than 100ms may hurt
+        performance by preventing jedi to build its cache.
+        """).tag(config=True)
+
     debug = Bool(default_value=False,
                  help='Enable debug for the Completer. Mostly print extra '
                       'information for experimental jedi integration.')\
@@ -1503,13 +1509,13 b' class IPCompleter(Completer):'
         #  - `.real` from 1 to 2
         # the current code does not (yet) check for such equivalence
         seen = set()
-        for c in self._completions(text, offset):
+        for c in self._completions(text, offset, _timeout=self.jedi_compute_type_timeout/1000):
             if c and (c in seen):
                 continue
             yield c
             seen.add(c)
 
-    def _completions(self, full_text: str, offset: int, *, _timeout=0.4)->Iterator[Completion]:
+    def _completions(self, full_text: str, offset: int, *, _timeout)->Iterator[Completion]:
         """
         Core completion module.Same signature as :any:`completions`, with the
         extra `timeout` parameter (in seconds).
@@ -1546,15 +1552,25 b' class IPCompleter(Completer):'
             full_text=full_text, cursor_line=cursor_line, cursor_pos=cursor_column)
 
         iter_jm = iter(jedi_matches)
-        for jm in iter_jm:
-            delta = len(jm.name_with_symbols) - len(jm.complete)
-            yield Completion(start=offset - delta, end=offset, text=jm.name_with_symbols, type=jm.type, _origin='jedi')
-            if time.monotonic() > deadline:
-                break
+        if _timeout:
+            for jm in iter_jm:
+                delta = len(jm.name_with_symbols) - len(jm.complete)
+                yield Completion(start=offset - delta,
+                                 end=offset,
+                                 text=jm.name_with_symbols,
+                                 type=jm.type,
+                                 _origin='jedi')
+
+                if time.monotonic() > deadline:
+                    break
 
         for jm in iter_jm:
             delta = len(jm.name_with_symbols) - len(jm.complete)
-            yield Completion(start=offset - delta, end=offset, text=jm.name_with_symbols+'?', type='<unknown>', _origin='jedi')
+            yield Completion(start=offset - delta,
+                             end=offset,
+                             text=jm.name_with_symbols,
+                             type='<unknown>',  # don't compute type for speed
+                             _origin='jedi')
 
 
         start_offset = before.rfind(matched_text)