Index: modules/toolbar/toolbar.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/toolbar/toolbar.module,v
retrieving revision 1.6
diff -u -p -r1.6 toolbar.module
--- modules/toolbar/toolbar.module	22 Aug 2009 14:34:22 -0000	1.6
+++ modules/toolbar/toolbar.module	24 Aug 2009 10:51:00 -0000
@@ -58,6 +58,17 @@ function toolbar_preprocess_page(&$vars)
 function toolbar_build() {
   global $user;
 
+  // Due to system_admin_menu_block_access(), building the toolbar links is
+  // expensive to render on each page, so we cache this information per-user.
+  // It is not possible to cache per role or combination of roles since
+  // access callbacks may use any arbitrary criteria not related to permissions
+  // to determine the visibility of menu links, however since the toolbar is
+  // likely to be accessible to a limited number of users, and is rendered on
+  // every page, it should still be more efficient than building it each time.
+  if ($cached = cache_get('toolbar:user:' . $GLOBALS['user']->uid, 'cache_block')) {
+    return $cached->data;
+  }
+
   $module_path = drupal_get_path('module', 'toolbar');
   $build = array(
     '#theme' => 'toolbar',
@@ -104,6 +115,8 @@ function toolbar_build() {
     '#attributes' => array('id' => 'toolbar-shortcuts'),
   );
 
+  cache_set('toolbar:user:' . $GLOBALS['user']->uid, $build, 'cache_block');
+
   return $build;
 }