diff --git a/jedi/api.py b/jedi/api.py
index 7bae0cb9..b0bf9053 100644
--- a/jedi/api.py
+++ b/jedi/api.py
@@ -425,15 +425,50 @@ class Script(object):
 
         This would return `None`.
         """
-        user_stmt = self.parser.user_stmt
-        if user_stmt is None or not isinstance(user_stmt, parsing.Statement):
-            return None
-        ass = helpers.fast_parent_copy(user_stmt.get_assignment_calls())
+        def check_user_stmt(user_stmt):
+            if user_stmt is None or not isinstance(user_stmt, parsing.Statement):
+                return None, 0
+            ass = helpers.fast_parent_copy(user_stmt.get_assignment_calls())
 
-        call, index, stop = helpers.scan_array_for_pos(ass, self.pos)
-        if call is None:
+            call, index, stop = helpers.scan_array_for_pos(ass, self.pos)
+            return call, index
+
+        def check_cache():
+            if self.source_path is None:
+                return None, 0
+
+            try:
+                timestamp, parser = builtin.CachedModule.cache[
+                                                            self.source_path]
+            except KeyError:
+                return None, 0
+            part_parser = self.module.get_part_parser()
+            user_stmt = part_parser.user_stmt
+            call, index = check_user_stmt(user_stmt)
+            if call:
+                old_stmt = parser.module.get_statement_for_position(self.pos)
+                if old_stmt is None:
+                    return None, 0
+                new_call, new_index = check_user_stmt(user_stmt)
+                if new_call:
+                    if str(new_call) == str(call) and index == new_index:
+                        return new_call, new_index
+                return None, 0
+            else:
+                raise NotFoundError()
+
+
+        try:
+            call, index = check_cache()
+        except NotFoundError:
             return None
 
+        if call is None:
+            user_stmt = self.parser.user_stmt
+            call, index = check_user_stmt(user_stmt)
+            if call is None:
+                return None
+
         origins = evaluate.follow_call(call)
 
         if len(origins) == 0:
diff --git a/jedi/modules.py b/jedi/modules.py
index 69064680..05d6c175 100644
--- a/jedi/modules.py
+++ b/jedi/modules.py
@@ -6,12 +6,13 @@ import re
 import tokenize
 import sys
 import os
+import time
 
 import parsing
 import builtin
 import debug
 import evaluate
-import time
+import settings
 
 
 class Module(builtin.CachedModule):
@@ -53,6 +54,7 @@ class ModuleWithCursor(Module):
         self._relevant_temp = None
 
         self.source = source
+        self._part_parser = None
 
     @property
     def parser(self):
@@ -67,7 +69,7 @@ class ModuleWithCursor(Module):
             # default), therefore fill the cache here.
             self._parser = parsing.PyFuzzyParser(self.source, self.path,
                                                                 self.position)
-            if self.path:
+            if self.path is not None:
                 builtin.CachedModule.cache[self.path] = time.time(), self._parser
         return self._parser
 
@@ -192,6 +194,21 @@ class ModuleWithCursor(Module):
         except IndexError:
             raise StopIteration()
 
+    def get_part_parser(self):
+        """ Returns a parser that contains only part of the source code. This
+        exists only because of performance reasons.
+        """
+        if self._part_parser:
+            return self._part_parser
+
+        # TODO check for docstrings
+        length = settings.part_line_length
+        offset = max(self.position[0] - length, 0)
+        s = '\n'.join(self.source.split('\n')[offset:offset + length])
+        self._part_parser = parsing.PyFuzzyParser(s, self.path, self.position,
+                                                        line_offset=offset)
+        return self._part_parser
+
 
 @evaluate.memoize_default([])
 def sys_path_with_modifications(module):
diff --git a/jedi/parsing.py b/jedi/parsing.py
index 0c1b9797..5f2f366d 100644
--- a/jedi/parsing.py
+++ b/jedi/parsing.py
@@ -1120,7 +1120,7 @@ class PyFuzzyParser(object):
     :type user_position: tuple(int, int)
     """
     def __init__(self, code, module_path=None, user_position=None,
-                                                            no_docstr=False):
+                                    no_docstr=False, line_offset=0):
         self.user_position = user_position
         self.user_scope = None
         self.user_stmt = None
@@ -1136,7 +1136,7 @@ class PyFuzzyParser(object):
 
         # Stuff to fix tokenize errors. The parser is pretty good in tolerating
         # any errors of tokenize and just parse ahead.
-        self._line_of_tokenize_restart = 0
+        self._line_of_tokenize_restart = line_offset
 
         self.parse()
 
diff --git a/jedi/settings.py b/jedi/settings.py
index 7981f62a..c164a675 100644
--- a/jedi/settings.py
+++ b/jedi/settings.py
@@ -62,3 +62,10 @@ additional_dynamic_modules = []
 max_function_recursion_level = 5
 max_until_execution_unique = 50
 max_executions = 1000
+
+# ----------------
+# various
+# ----------------
+
+# Size of the current code part, which is used to speed up parsing.
+part_line_length = 20
diff --git a/test/regression.py b/test/regression.py
index 8c22a02c..797e8de8 100755
--- a/test/regression.py
+++ b/test/regression.py
@@ -31,6 +31,13 @@ class TestRegression(unittest.TestCase):
         script = api.Script(src, pos[0], pos[1], '')
         return script.get_in_function_call()
 
+    def test_part_parser(self):
+        """ test the get_in_function_call speedups """
+        s = '\n' * 100 + 'abs('
+        pos = 101, 4
+        self.get_in_function_call(s, pos)
+        assert self.get_in_function_call(s, pos)
+
     def test_get_definition_cursor(self):
 
         s = ("class A():\n"