diff -r a0b2b5abf88c Python/marshal.c
--- a/Python/marshal.c	Wed Jan 28 17:11:12 2015 +0200
+++ b/Python/marshal.c	Wed Jan 28 17:14:14 2015 +0200
@@ -72,7 +72,12 @@ typedef struct {
     char *end;
     char *buf;
     Py_ssize_t buf_size;
+    unsigned int refs_count;
     PyObject *refs; /* dict on marshal, list on unmarshal */
+    PyObject *int_refs;
+    PyObject *float_refs;
+    PyObject *complex_refs;
+    PyObject *str_refs;
     int version;
 } WFILE;
 
@@ -223,8 +228,9 @@ w_PyLong(const PyLongObject *ob, char fl
 static int
 w_ref(PyObject *v, char *flag, WFILE *p)
 {
-    PyObject *id;
+    PyObject *id = v;
     PyObject *idx;
+    PyObject *refs = NULL;
 
     if (p->version < 3 || p->refs == NULL)
         return 0; /* not writing object references */
@@ -233,14 +239,30 @@ w_ref(PyObject *v, char *flag, WFILE *p)
     if (Py_REFCNT(v) == 1)
         return 0;
 
-    id = PyLong_FromVoidPtr((void*)v);
-    if (id == NULL)
-        goto err;
-    idx = PyDict_GetItem(p->refs, id);
+    if (PyUnicode_CheckExact(v)) {
+        if (PyUnicode_GET_LENGTH(v) < 1000)
+            refs = p->str_refs;
+    }
+    else if (PyLong_CheckExact(v))
+        refs = p->int_refs;
+    else if (PyFloat_CheckExact(v))
+        refs = p->float_refs;
+    else if (PyComplex_CheckExact(v))
+        refs = p->complex_refs;
+
+    if (refs == NULL) {
+        refs = p->refs;
+        id = PyLong_FromVoidPtr((void*)v);
+        if (id == NULL)
+            goto err;
+    }
+
+    idx = PyDict_GetItem(refs, id);
     if (idx != NULL) {
         /* write the reference index to the stream */
         long w = PyLong_AsLong(idx);
-        Py_DECREF(id);
+        if (id != v)
+            Py_DECREF(id);
         if (w == -1 && PyErr_Occurred()) {
             goto err;
         }
@@ -251,18 +273,20 @@ w_ref(PyObject *v, char *flag, WFILE *p)
         return 1;
     } else {
         int ok;
-        Py_ssize_t s = PyDict_Size(p->refs);
+        Py_ssize_t s = p->refs_count;
         /* we don't support long indices */
         if (s >= 0x7fffffff) {
             PyErr_SetString(PyExc_ValueError, "too many objects");
             goto err;
         }
         idx = PyLong_FromSsize_t(s);
-        ok = idx && PyDict_SetItem(p->refs, id, idx) == 0;
-        Py_DECREF(id);
+        ok = idx && PyDict_SetItem(refs, id, idx) == 0;
+        if (id != v)
+            Py_DECREF(id);
         Py_XDECREF(idx);
         if (!ok)
             goto err;
+        p->refs_count++;
         *flag |= FLAG_REF;
         return 0;
     }
@@ -558,6 +582,41 @@ PyMarshal_WriteLongToFile(long x, FILE *
     w_long(x, &wf);
 }
 
+static int
+w_init_refs(WFILE *wf, int version)
+{
+    wf->refs = NULL;
+    wf->int_refs = NULL;
+    wf->float_refs = NULL;
+    wf->complex_refs = NULL;
+    wf->str_refs = NULL;
+    if (version >= 3) {
+        wf->refs_count = 0;
+        if ((wf->int_refs = PyDict_New()) == NULL ||
+            (wf->float_refs = PyDict_New()) == NULL ||
+            (wf->complex_refs = PyDict_New()) == NULL ||
+            (wf->str_refs = PyDict_New()) == NULL ||
+            (wf->refs = PyDict_New()) == NULL) {
+            Py_CLEAR(wf->int_refs);
+            Py_CLEAR(wf->float_refs);
+            Py_CLEAR(wf->complex_refs);
+            Py_CLEAR(wf->str_refs);
+            return -1;
+        }
+    }
+    return 0;
+}
+
+static void
+w_clear(WFILE *wf)
+{
+    Py_XDECREF(wf->refs);
+    Py_XDECREF(wf->int_refs);
+    Py_XDECREF(wf->float_refs);
+    Py_XDECREF(wf->complex_refs);
+    Py_XDECREF(wf->str_refs);
+}
+
 void
 PyMarshal_WriteObjectToFile(PyObject *x, FILE *fp, int version)
 {
@@ -565,14 +624,11 @@ PyMarshal_WriteObjectToFile(PyObject *x,
     wf.fp = fp;
     wf.error = WFERR_OK;
     wf.depth = 0;
-    if (version >= 3) {
-        if ((wf.refs = PyDict_New()) == NULL)
-            return; /* caller mush check PyErr_Occurred() */
-    } else
-        wf.refs = NULL;
+    if (w_init_refs(&wf, version))
+        return; /* caller mush check PyErr_Occurred() */
     wf.version = version;
     w_object(x, &wf);
-    Py_XDECREF(wf.refs);
+    w_clear(&wf);
 }
 
 typedef WFILE RFILE; /* Same struct with different invariants */
@@ -1519,15 +1575,12 @@ PyMarshal_WriteObjectToString(PyObject *
     wf.error = WFERR_OK;
     wf.depth = 0;
     wf.version = version;
-    if (version >= 3) {
-        if ((wf.refs = PyDict_New()) == NULL) {
-            Py_DECREF(wf.str);
-            return NULL;
-        }
-    } else
-        wf.refs = NULL;
+    if (w_init_refs(&wf, version)) {
+        Py_DECREF(wf.str);
+        return NULL;
+    }
     w_object(x, &wf);
-    Py_XDECREF(wf.refs);
+    w_clear(&wf);
     if (wf.str != NULL) {
         char *base = PyBytes_AS_STRING((PyBytesObject *)wf.str);
         if (wf.ptr - base > PY_SSIZE_T_MAX) {