diff -r 058bb3dc685f -r 0b59724cb3f2 cubicweb/_gcdebug.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cubicweb/_gcdebug.py	Sat Jan 16 13:48:51 2016 +0100
@@ -0,0 +1,112 @@
+# copyright 2003-2010 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
+# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
+#
+# This file is part of CubicWeb.
+#
+# CubicWeb is free software: you can redistribute it and/or modify it under the
+# terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation, either version 2.1 of the License, or (at your option)
+# any later version.
+#
+# CubicWeb is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License along
+# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
+from __future__ import print_function
+
+import gc, types, weakref
+
+from cubicweb.schema import CubicWebRelationSchema, CubicWebEntitySchema
+try:
+    from cubicweb.web.request import _NeedAuthAccessMock
+except ImportError:
+    _NeedAuthAccessMock = None
+
+listiterator = type(iter([]))
+
+IGNORE_CLASSES = (
+    type, tuple, dict, list, set, frozenset, type(len),
+    weakref.ref, weakref.WeakKeyDictionary,
+    listiterator,
+    property, classmethod,
+    types.ModuleType, types.FunctionType, types.MethodType,
+    types.MemberDescriptorType, types.GetSetDescriptorType,
+    )
+if _NeedAuthAccessMock is not None:
+    IGNORE_CLASSES = IGNORE_CLASSES + (_NeedAuthAccessMock,)
+
+def _get_counted_class(obj, classes):
+    for cls in classes:
+        if isinstance(obj, cls):
+            return cls
+    raise AssertionError()
+
+def gc_info(countclasses,
+            ignoreclasses=IGNORE_CLASSES,
+            viewreferrersclasses=(), showobjs=False, maxlevel=1):
+    gc.collect()
+    gc.collect()
+    counters = {}
+    ocounters = {}
+    for obj in gc.get_objects():
+        if isinstance(obj, countclasses):
+            cls = _get_counted_class(obj, countclasses)
+            try:
+                counters[cls.__name__] += 1
+            except KeyError:
+                counters[cls.__name__] = 1
+        elif not isinstance(obj, ignoreclasses):
+            try:
+                key = '%s.%s' % (obj.__class__.__module__,
+                                 obj.__class__.__name__)
+            except AttributeError:
+                key = str(obj)
+            try:
+                ocounters[key] += 1
+            except KeyError:
+                ocounters[key] = 1
+        if isinstance(obj, viewreferrersclasses):
+            print('   ', obj, referrers(obj, showobjs, maxlevel))
+    garbage = [repr(obj) for obj in gc.garbage]
+    return counters, ocounters, garbage
+
+
+def referrers(obj, showobj=False, maxlevel=1):
+    objreferrers = _referrers(obj, maxlevel)
+    try:
+        return sorted(set((type(x), showobj and x or getattr(x, '__name__', '%#x' % id(x)))
+                          for x in objreferrers))
+    except TypeError:
+        s = set()
+        unhashable = []
+        for x in objreferrers:
+            try:
+                s.add(x)
+            except TypeError:
+                unhashable.append(x)
+        return sorted(s) + unhashable
+
+def _referrers(obj, maxlevel, _seen=None, _level=0):
+    interesting = []
+    if _seen is None:
+        _seen = set()
+    for x in gc.get_referrers(obj):
+        if id(x) in _seen:
+            continue
+        _seen.add(id(x))
+        if isinstance(x, types.FrameType):
+            continue
+        if isinstance(x, (CubicWebRelationSchema, CubicWebEntitySchema)):
+            continue
+        if isinstance(x, (list, tuple, set, dict, listiterator)):
+            if _level >= maxlevel:
+                pass
+                #interesting.append(x)
+            else:
+                interesting += _referrers(x, maxlevel, _seen, _level+1)
+        else:
+            interesting.append(x)
+    return interesting