diff --git a/modules/field/field.info.inc b/modules/field/field.info.inc
index 6b172dd..60be42d 100644
--- a/modules/field/field.info.inc
+++ b/modules/field/field.info.inc
@@ -6,6 +6,187 @@
  */
 
 /**
+ * Extends DrupalCacheArray to allow dynamic building of the field info cache.
+ */
+class FieldInfoFieldCache extends DrupalCacheArray {
+  protected $fields_by_id;
+  protected $field_ids;
+
+  public function __construct() {
+    // We explicitely do not call the parent constructor, because we handle
+    // persistent caching differently.
+    $this->field_ids = array();
+    $this->fields_by_id = array();
+    $this->bin = 'cache_field';
+  }
+
+  public function offsetGet($offset) {
+    if (isset($this->storage[$offset]) || array_key_exists($offset, $this->storage)) {
+      $value = $this->storage[$offset];
+    }
+    elseif ($cached = cache_get('info_fields:' . $offset, $this->bin)) {
+      $value = $cached->data;
+      // Extract the 'fields' part and store them globally.
+      $this->fields_by_id += $value['fields_by_id'];
+      // @todo : kind of absurd, we're readding it below.
+      unset($value['fields']);
+      $this->storage[$offset] = $value;
+    }
+    else {
+      $value = $this->resolveCacheMiss($offset);
+    }
+
+    // Additionally, populate actual fields from ids.
+    foreach ($value['field_ids'] as $field_id) {
+      $value['fields_by_id'][$field_id] = $this->fields_by_id[$field_id];
+    }
+
+    return $value;
+  }
+
+  protected function resolveCacheMiss($offset) {
+    list($entity_type, $bundle) = explode(':', $offset);
+    $value = array(
+      'instances' => array(),
+      'field_ids' => array(),
+    );
+
+    $fields = field_read_fields(array(), array('include_deleted' => 1));
+    $field_bundles = array();
+
+    foreach (field_read_instances() as $instance) {
+      $field_id = $instance['field_id'];
+      $field_name = $instance['field_name'];
+
+      if ($instance['entity_type'] == $entity_type && $instance['bundle'] == $bundle) {
+
+        // Populate the global array of fields and field ids.
+        if (!isset($this->fields_by_id[$field_id])) {
+          $field = _field_info_prepare_field($fields[$field_id]);
+          $this->fields_by_id[$field_id] = $field;
+          if (!$field['deleted']) {
+            $this->field_ids[$field_name] = $field_id;
+          }
+        }
+        else {
+          $field = $this->fields_by_id[$field_id];
+        }
+
+        $instance = _field_info_prepare_instance($instance, $field);
+        $value['instances'][$field_name] = $instance;
+        // @todo : key by field name ?
+        $value['field_ids'][] = $field_id;
+      }
+
+      // Collect the list of bundles for all fields.
+      $field_bundles[$field_id][$instance['entity_type']][] = $instance['bundle'];
+    }
+
+    // Enrich field definitions with the list of bundles where they have
+    // instances. Note: Deleted fields are not enriched because all of their
+    // instances are deleted, too, and are thus not iterated here.
+    foreach ($value['field_ids'] as $field_id) {
+      $this->fields_by_id[$field_id]['bundles'] = $field_bundles[$field_id];
+    }
+
+    $this->storage[$offset] = $value;
+    $this->persist($offset);
+    
+    return $value;
+  }
+
+  public function __destruct() {
+    foreach ($this->keysToPersist as $offset => $persist) {
+      if ($persist) {
+        $value = $this->storage[$offset];
+        // Add field definitions from the global list of fields.
+        foreach ($value['field_ids'] as $field_id) {
+          $value['fields_by_id'][$field_id] = $this->fields_by_id[$field_id];
+          // @todo : persist $this->field_ids ?
+        }
+        $this->set('info_fields:' . $offset, $value, $this->bin);
+      }
+    }
+  }
+
+  /**
+   * Don't look at that, this is the code from current _field_info_collate_fields().
+   */
+  function dummy_old_code() {
+    $definitions = array(
+      'field_ids' => field_read_fields(array(), array('include_deleted' => 1)),
+      'instances' => field_read_instances(),
+    );
+
+    // Populate 'fields' with all fields, keyed by ID.
+    $info['fields'] = array();
+    foreach ($definitions['field_ids'] as $key => $field) {
+      $info['fields'][$key] = $definitions['field_ids'][$key] = _field_info_prepare_field($field);
+    }
+
+    // Build an array of field IDs for non-deleted fields, keyed by name.
+    $info['field_ids'] = array();
+    foreach ($info['fields'] as $key => $field) {
+      if (!$field['deleted']) {
+        $info['field_ids'][$field['field_name']] = $key;
+      }
+    }
+
+    // Populate 'instances'. Only non-deleted instances are considered.
+    $info['instances'] = array();
+    foreach (field_info_bundles() as $entity_type => $bundles) {
+      foreach ($bundles as $bundle => $bundle_info) {
+        $info['instances'][$entity_type][$bundle] = array();
+      }
+    }
+    foreach ($definitions['instances'] as $instance) {
+      $field = $info['fields'][$instance['field_id']];
+      $instance = _field_info_prepare_instance($instance, $field);
+      $info['instances'][$instance['entity_type']][$instance['bundle']][$instance['field_name']] = $instance;
+      // Enrich field definitions with the list of bundles where they have
+      // instances. NOTE: Deleted fields in $info['field_ids'] are not
+      // enriched because all of their instances are deleted, too, and
+      // are thus not in $definitions['instances'].
+      $info['fields'][$instance['field_id']]['bundles'][$instance['entity_type']][] = $instance['bundle'];
+    }
+
+    // Populate 'extra_fields'.
+    $extra = module_invoke_all('field_extra_fields');
+    drupal_alter('field_extra_fields', $extra);
+    // Merge in saved settings.
+    foreach ($extra as $entity_type => $bundles) {
+      foreach ($bundles as $bundle => $extra_fields) {
+        $extra_fields = _field_info_prepare_extra_fields($extra_fields, $entity_type, $bundle);
+        $info['extra_fields'][$entity_type][$bundle] = $extra_fields;
+      }
+    }
+  }
+}
+
+function _field_info_field_cache($reset = FALSE) {
+  static $info;
+
+  if ($reset) {
+    $info = NULL;
+  }
+  elseif (!isset($info)) {
+    $info = new FieldInfoFieldCache();
+  }
+  
+  return $info;
+}
+
+function dummy_test() {
+  $info = _field_info_field_cache();
+  dsm($info['node:article'], '$info[node:article]');
+  dsm(cache_get('info_fields:node:article', 'cache_field'), 'cache node:article');
+  dsm($info, '$info');
+  dsm($info['node:page'], '$info[node:page]');
+  dsm(cache_get('info_fields:node:page', 'cache_field'), 'cache node:page');
+  dsm($info, '$info');
+}
+
+/**
  * @defgroup field_info Field Info API
  * @{
  * Obtain information about Field API configuration.
@@ -178,6 +359,7 @@ function _field_info_collate_types($reset = FALSE) {
  */
 function _field_info_collate_fields($reset = FALSE) {
   static $info;
+  static $schema;
 
   if ($reset) {
     $info = NULL;
@@ -587,6 +769,7 @@ function field_info_bundles($entity_type = NULL) {
  *   which this field belongs keyed by entity type.
  */
 function field_info_fields() {
+  // Do not persist anything ?
   $fields = array();
   $info = _field_info_collate_fields();
   foreach ($info['fields'] as $key => $field) {
@@ -613,6 +796,8 @@ function field_info_fields() {
  * @see field_info_field_by_id()
  */
 function field_info_field($field_name) {
+  // Persist ?
+  
   $info = _field_info_collate_fields();
   if (isset($info['field_ids'][$field_name])) {
     return $info['fields'][$info['field_ids'][$field_name]];
@@ -634,6 +819,8 @@ function field_info_field($field_name) {
  * @see field_info_field()
  */
 function field_info_field_by_id($field_id) {
+  // Persist ?
+  
   $info = _field_info_collate_fields();
   if (isset($info['fields'][$field_id])) {
     return $info['fields'][$field_id];
@@ -655,6 +842,8 @@ function field_info_field_by_id($field_id) {
  * @see field_info_field_by_id()
  */
 function field_info_field_by_ids() {
+  // Do not persist anything ?
+  
   $info = _field_info_collate_fields();
   return $info['fields'];
 }
@@ -674,6 +863,8 @@ function field_info_field_by_ids() {
  *   all instances for that bundle.
  */
 function field_info_instances($entity_type = NULL, $bundle_name = NULL) {
+  // If entity type + bundle : persist in the cache.
+
   $info = _field_info_collate_fields();
   if (!isset($entity_type)) {
     return $info['instances'];
@@ -698,6 +889,8 @@ function field_info_instances($entity_type = NULL, $bundle_name = NULL) {
  *   The bundle name for the instance.
  */
 function field_info_instance($entity_type, $field_name, $bundle_name) {
+  // Persist the instance and field definition.
+
   $info = _field_info_collate_fields();
   if (isset($info['instances'][$entity_type][$bundle_name][$field_name])) {
     return $info['instances'][$entity_type][$bundle_name][$field_name];
diff --git a/modules/field_ui/field_ui.admin.inc b/modules/field_ui/field_ui.admin.inc
index 9cd5ee1..e51f38a 100644
--- a/modules/field_ui/field_ui.admin.inc
+++ b/modules/field_ui/field_ui.admin.inc
@@ -595,6 +595,8 @@ function field_ui_field_overview_form($form, &$form_state, $entity_type, $bundle
   // Add settings for the update selects behavior.
   $js_fields = array();
   foreach ($existing_field_options as $field_name => $fields) {
+    // @todo : we probably want to avoid filling the field / instance caches here
+    // -> use field_info_fields() / field_info_instances() ?
     $field = field_info_field($field_name);
     $instance = field_info_instance($form['#entity_type'], $field_name, $form['#bundle']);
     $js_fields[$field_name] = array('label' => $instance['label'], 'type' => $field['type'], 'widget' => $instance['widget']['type']);
@@ -1486,6 +1488,7 @@ function field_ui_existing_field_options($entity_type, $bundle) {
           // - fields that that shoud not be added via user interface.
 
           if (empty($field['locked'])
+            // @todo watch this.
             && !field_info_instance($entity_type, $field['field_name'], $bundle)
             && (empty($field['entity_types']) || in_array($entity_type, $field['entity_types']))
             && empty($field_types[$field['type']]['no_ui'])) {