wip: benchmarks

Keep a bitset of positions where the array contains
objects, and check those for reusable objects whenever
we need a new object.

We still keep the low-bit marking of string pointers,
so we can implement g_list_model_get_item without having
to consult the bitset.

In scrolling through the words demo, this keeps the
number of live string objects at ~200.

gtk/gtkstringlist.c

@@ -25,6 +25,7 @@
 #include "gtkbuilderprivate.h"
 #include "gtkintl.h"
 #include "gtkprivate.h"
+#include "gtkbitset.h"
 
 /**
  * SECTION:gtkstringlist
@@ -145,23 +146,6 @@ gtk_string_object_class_init (GtkStringObjectClass *class)
 
 }
 
-static GtkStringObject *
-gtk_string_object_new_take (char *string)
-{
-  GtkStringObject *obj;
-
-  obj = g_object_new (GTK_TYPE_STRING_OBJECT, NULL);
-  obj->string = string;
-
-  return obj;
-}
-
-static GtkStringObject *
-gtk_string_object_new (const char *string)
-{
-  return gtk_string_object_new_take (g_strdup (string));
-}
-
 /**
  * gtk_string_object_get_string:
  * @self: a #GtkStringObject
@@ -182,7 +166,8 @@ struct _GtkStringList
 {
   GObject parent_instance;
 
-  GSequence *items;
+  GPtrArray *items;
+  GtkBitset *objects;
 };
 
 struct _GtkStringListClass
@@ -201,7 +186,56 @@ gtk_string_list_get_n_items (GListModel *list)
 {
   GtkStringList *self = GTK_STRING_LIST (list);
 
-  return g_sequence_get_length (self->items);
+  return self->items->len;
+}
+
+static inline gboolean
+IS_STRING (gpointer item)
+{
+  return GPOINTER_TO_INT (item) & 0x1;
+}
+
+static inline gpointer
+TO_STRING (gpointer item)
+{
+  return GINT_TO_POINTER (GPOINTER_TO_INT (item) & ~0x1);
+}
+
+static inline gpointer
+MAKE_STRING (const char *str)
+{
+  return GINT_TO_POINTER (GPOINTER_TO_INT (str) | 0x1);
+}
+
+static GtkStringObject *
+find_unused_object (GtkStringList *self)
+{
+  GtkBitsetIter iter;
+  guint position;
+  gpointer item;
+
+  if (gtk_bitset_iter_init_first (&iter, self->objects, &position))
+    {
+      do
+        {
+          item = g_ptr_array_index (self->items, position);
+          g_assert (!IS_STRING (item));
+          if (G_OBJECT (item)->ref_count == 1)
+            {
+              GtkStringObject *obj;
+
+              obj = GTK_STRING_OBJECT (item);
+              g_ptr_array_index (self->items, position) = MAKE_STRING (obj->string);
+              obj->string = NULL;
+
+              gtk_bitset_remove (self->objects, position);
+
+              return obj;
+            }
+        } while (gtk_bitset_iter_next (&iter, &position));
+    }
+
+  return NULL;
 }
 
 static gpointer
@@ -209,14 +243,30 @@ gtk_string_list_get_item (GListModel *list,
                           guint       position)
 {
   GtkStringList *self = GTK_STRING_LIST (list);
-  GSequenceIter *iter;
+  gpointer item;
 
-  iter = g_sequence_get_iter_at_pos (self->items, position);
-
-  if (g_sequence_iter_is_end (iter))
+  if (position >= self->items->len)
     return NULL;
-  else
-    return g_object_ref (g_sequence_get (iter));
+
+  item = g_ptr_array_index (self->items, position);
+  if (IS_STRING (item))
+    {
+      GtkStringObject *obj;
+
+      obj = find_unused_object (self);
+      if (!obj)
+        obj = g_object_new (GTK_TYPE_STRING_OBJECT, NULL);
+
+      obj->string = TO_STRING (item);
+      g_ptr_array_index (self->items, position) = obj;
+      gtk_bitset_add (self->objects, position);
+
+      item = obj;
+    }
+
+  g_print ("live string objects: %lu\n", gtk_bitset_get_size (self->objects));
+
+  return g_object_ref (item);
 }
 
 static void
@@ -323,7 +373,7 @@ item_end_element (GtkBuildableParseContext  *context,
           g_string_assign (data->string, translated);
         }
 
-      g_sequence_append (data->list->items, gtk_string_object_new (data->string->str));
+      g_ptr_array_add (data->list->items, MAKE_STRING (g_strdup (data->string->str)));
     }
 
   data->translatable = FALSE;
@@ -403,7 +453,8 @@ gtk_string_list_dispose (GObject *object)
 {
   GtkStringList *self = GTK_STRING_LIST (object);
 
-  g_clear_pointer (&self->items, g_sequence_free);
+  g_clear_pointer (&self->items, g_ptr_array_unref);
+  g_clear_pointer (&self->objects, gtk_bitset_unref);
 
   G_OBJECT_CLASS (gtk_string_list_parent_class)->dispose (object);
 }
@@ -416,10 +467,20 @@ gtk_string_list_class_init (GtkStringListClass *class)
   gobject_class->dispose = gtk_string_list_dispose;
 }
 
+static void
+free_string_or_object (gpointer data)
+{
+  if (IS_STRING (data))
+    g_free (TO_STRING (data));
+  else
+    g_object_unref (data);
+}
+
 static void
 gtk_string_list_init (GtkStringList *self)
 {
-  self->items = g_sequence_new (g_object_unref);
+  self->items = g_ptr_array_new_full (32, free_string_or_object);
+  self->objects = gtk_bitset_new_empty ();
 }
 
 /**
@@ -468,39 +529,36 @@ gtk_string_list_splice (GtkStringList      *self,
                         guint               n_removals,
                         const char * const *additions)
 {
-  GSequenceIter *it;
-  guint add, n_items;
+  guint n_items;
+  guint i;
+  guint n_additions;
+  gpointer item;
 
   g_return_if_fail (GTK_IS_STRING_LIST (self));
   g_return_if_fail (position + n_removals >= position); /* overflow */
 
-  n_items = g_sequence_get_length (self->items);
+  n_items = self->items->len;
   g_return_if_fail (position + n_removals <= n_items);
 
-  it = g_sequence_get_iter_at_pos (self->items, position);
-
-  if (n_removals)
-    {
-      GSequenceIter *end;
-
-      end = g_sequence_iter_move (it, n_removals);
-      g_sequence_remove_range (it, end);
-
-      it = end;
-    }
+  for (i = 0; i < n_removals; i++)
+    g_ptr_array_remove_index (self->items, position);
 
   if (additions)
     {
-      for (add = 0; additions[add]; add++)
+      for (i = 0; additions[i]; i++)
         {
-          g_sequence_insert_before (it, gtk_string_object_new (additions[add]));
+          item = MAKE_STRING (g_strdup (additions[i]));
+          g_ptr_array_insert (self->items, position + i, item);
         }
+      n_additions = i;
     }
   else
-    add = 0;
+    n_additions = 0;
 
-  if (n_removals || add)
-    g_list_model_items_changed (G_LIST_MODEL (self), position, n_removals, add);
+  gtk_bitset_slice (self->objects, position, n_removals, n_additions);
+
+  if (n_removals || n_additions)
+    g_list_model_items_changed (G_LIST_MODEL (self), position, n_removals, n_additions);
 }
 
 /**
@@ -518,11 +576,13 @@ gtk_string_list_append (GtkStringList *self,
                         const char    *string)
 {
   guint n_items;
+  gpointer item;
 
   g_return_if_fail (GTK_IS_STRING_LIST (self));
 
-  n_items = g_sequence_get_length (self->items);
-  g_sequence_append (self->items, gtk_string_object_new (string));
+  n_items = self->items->len;
+  item = MAKE_STRING (g_strdup (string));
+  g_ptr_array_add (self->items, item);
 
   g_list_model_items_changed (G_LIST_MODEL (self), n_items, 0, 1);
 }
@@ -547,11 +607,13 @@ gtk_string_list_take (GtkStringList *self,
                       char          *string)
 {
   guint n_items;
+  gpointer item;
 
   g_return_if_fail (GTK_IS_STRING_LIST (self));
 
-  n_items = g_sequence_get_length (self->items);
-  g_sequence_append (self->items, gtk_string_object_new_take (string));
+  n_items = self->items->len;
+  item = MAKE_STRING (string);
+  g_ptr_array_add (self->items, item);
 
   g_list_model_items_changed (G_LIST_MODEL (self), n_items, 0, 1);
 }
@@ -568,14 +630,13 @@ void
 gtk_string_list_remove (GtkStringList *self,
                         guint          position)
 {
-  GSequenceIter *iter;
-
   g_return_if_fail (GTK_IS_STRING_LIST (self));
 
-  iter = g_sequence_get_iter_at_pos (self->items, position);
-  g_return_if_fail (!g_sequence_iter_is_end (iter));
+  if (position >= self->items->len)
+    return;
 
-  g_sequence_remove (iter);
+  g_ptr_array_remove_index (self->items, position);
+  gtk_bitset_slice (self->objects, position, 1, 0);
 
   g_list_model_items_changed (G_LIST_MODEL (self), position, 1, 0);
 }
@@ -597,20 +658,14 @@ const char *
 gtk_string_list_get_string (GtkStringList *self,
                             guint          position)
 {
-  GSequenceIter *iter;
+  gpointer item;
 
   g_return_val_if_fail (GTK_IS_STRING_LIST (self), NULL);
 
-  iter = g_sequence_get_iter_at_pos (self->items, position);
+  item = g_ptr_array_index (self->items, position);
 
-  if (g_sequence_iter_is_end (iter))
-    {
-      return NULL;
-    }
+  if (IS_STRING (item))
+    return (const char *)TO_STRING (item);
   else
-    {
-      GtkStringObject *obj = g_sequence_get (iter);
-
-      return obj->string;
-    }
+    return GTK_STRING_OBJECT (item)->string;
 }

testsuite/gtk/listmodel-performance.c

@@ -0,0 +1,91 @@
+#include <gtk/gtk.h>
+
+static GObject *
+get_object (const char *string)
+{
+  GtkStringList *list;
+  GObject *obj;
+
+  list = gtk_string_list_new ((const char *[]){string, NULL});
+  obj = g_list_model_get_item (G_LIST_MODEL (list), 0);
+  g_object_unref (list);
+
+  return obj;
+}
+
+static GListModel *
+make_store (guint n_items)
+{
+  GListStore *store;
+  guint i;
+
+  store = g_list_store_new (GTK_TYPE_STRING_OBJECT);
+
+  for (i = 0; i < n_items; i++)
+    {
+      char *string;
+      GObject *obj;
+
+      string = g_strdup_printf ("item %d", i);
+      obj = get_object (string);
+      g_list_store_append (store, obj);
+      g_object_unref (obj);
+      g_free (string);
+    }
+
+  return G_LIST_MODEL (store);
+}
+
+static void
+do_random_access (guint size)
+{
+  GListModel *model;
+  guint i;
+  guint position;
+  GtkStringObject *obj;
+  gint64 start, end;
+  guint iterations = 10000000;
+
+  model = make_store (size);
+
+  start = g_get_monotonic_time ();
+
+  for (i = 0; i < iterations; i++)
+    {
+      position = g_random_int_range (0, size);
+      obj = g_list_model_get_item (model, position);
+      if (g_getenv ("PRINT_ACCESS"))
+        g_print ("%s", gtk_string_object_get_string (obj));
+      g_object_unref (obj);
+    }
+
+  end = g_get_monotonic_time ();
+
+  g_print ("size %u: %g accesses per second\n",
+           size,
+           (iterations / (double) G_TIME_SPAN_SECOND) * ((double)(end - start)));
+
+  g_object_unref (model);
+}
+
+static void
+random_access (void)
+{
+  do_random_access (1e1);
+  do_random_access (1e2);
+  do_random_access (1e3);
+  do_random_access (1e4);
+  do_random_access (1e5);
+  do_random_access (1e6);
+  do_random_access (1e7);
+}
+
+int
+main (int argc, char *argv[])
+{
+  gtk_test_init (&argc, &argv);
+
+  g_test_add_func ("/liststore/random-access", random_access);
+
+  return g_test_run ();
+}

testsuite/gtk/meson.build

@@ -76,6 +76,7 @@ tests = [
   ['revealer-size'],
   ['widgetorder'],
   ['widget-refcount'],
+  ['listmodel-performance'],
 ]
 
 # Tests that are expected to fail