diff -urN ./includes/common.inc ../drupal-6.13-pathcache/includes/common.inc
--- ./includes/common.inc	2009-07-01 15:51:55.000000000 -0500
+++ ../drupal-6.13-pathcache/includes/common.inc	2009-07-14 09:19:12.000000000 -0500
@@ -1581,7 +1581,7 @@
   if (variable_get('cache', CACHE_DISABLED) != CACHE_DISABLED) {
     page_set_cache();
   }
-
+  drupal_cache_system_paths();
   module_invoke_all('exit');
 }
 
diff -urN ./includes/path.inc ../drupal-6.13-pathcache/includes/path.inc
--- ./includes/path.inc	2008-10-13 16:06:41.000000000 -0500
+++ ../drupal-6.13-pathcache/includes/path.inc	2009-07-14 17:22:04.000000000 -0500
@@ -46,7 +46,12 @@
 function drupal_lookup_path($action, $path = '', $path_language = '') {
   global $language;
   // $map is an array with language keys, holding arrays of Drupal paths to alias relations
-  static $map = array(), $no_src = array(), $count;
+  $map = &drupal_static(__FUNCTION__, array());
+  $no_src = &drupal_static(__FUNCTION__ . ':no_src', array());
+  $count = &drupal_static(__FUNCTION__ . ':count');
+  $system_paths = &drupal_static(__FUNCTION__ . ':system_paths');
+  $no_aliases = &drupal_static(__FUNCTION__ . ':no_alias', array());
+  $first_call = &drupal_static(__FUNCTION__ . ':first_call', TRUE);
 
   $path_language = $path_language ? $path_language : $language->language;
 
@@ -59,16 +64,43 @@
     $map = array();
     $no_src = array();
     $count = NULL;
+    $system_paths = array();
+    $no_aliases = array();
   }
   elseif ($count > 0 && $path != '') {
     if ($action == 'alias') {
+      // During the first call to drupal_lookup_path() per language, load the
+      // expected system paths for the page from cache.
+      if ($first_call) {
+        $first_call = FALSE;
+        $map[$path_language] = array();
+        // Load system paths from cache.
+        $cid = $_GET['q'];
+        if ($cache = cache_get($cid, 'cache_path')) {
+          // Now fetch the aliases corresponding to these system paths.
+          // We order by ASC and overwrite array keys to ensure the correct
+          // alias is used when there are multiple aliases per path.
+          $system_paths = $cache->data;
+          $placeholders = db_placeholders($system_paths, 'varchar');
+          $result = db_query("SELECT src, dst FROM {url_alias} WHERE src IN($placeholders) AND language IN(%s, '') ORDER BY language ASC", $system_paths, $path_language
+          );
+          while ($record = db_fetch_object($result)) {
+            $map[$path_language][$record->src] = $record->dst;
+          }
+          // Keep a record of paths with no alias to avoid querying twice.
+          $no_aliases[$path_language] = array_flip(array_diff($system_paths, array_keys($map[$path_language])));
+        }
+      }
+      // If the alias has already been loaded, return it.
       if (isset($map[$path_language][$path])) {
         return $map[$path_language][$path];
       }
-      // Get the most fitting result falling back with alias without language
-      $alias = db_result(db_query("SELECT dst FROM {url_alias} WHERE src = '%s' AND language IN('%s', '') ORDER BY language DESC", $path, $path_language));
-      $map[$path_language][$path] = $alias;
-      return $alias;
+      // For system paths which were not cached, query aliases individually.
+      else if (!isset($no_aliases[$path_language][$path])) {
+        $alias = db_result(db_query("SELECT dst FROM {url_alias} WHERE src = '%s' AND language IN('%s', '') ORDER BY language DESC", $path, $path_language));
+        $map[$path_language][$path] = $alias;
+        return $alias;
+      }
     }
     // Check $no_src for this $path in case we've already determined that there
     // isn't a path that has this alias
@@ -95,6 +127,33 @@
 }
 
 /**
+ * Cache system paths for a page.
+ *
+ * Cache an array of the system paths available on each page. We assume
+ * that aiases will be needed for the majority of these paths during
+ * subsequent requests, and load them in a single query during
+ * drupal_lookup_path().
+ */
+function drupal_cache_system_paths() {
+  // Check if the system paths for this page were loaded from cache in this
+  // request to avoid writing to cache on every request.
+  $system_paths = &drupal_static('drupal_lookup_path:system_paths', array());
+  if (!$system_paths) {
+    // The static $map array used by drupal_lookup_path() includes all
+    // system paths for the page request.
+    $map = &drupal_static('drupal_lookup_path', array());
+
+    // Generate a cache ID (cid) specifically for this page.
+    $cid = $_GET['q'];
+    if ($paths = current($map)) {
+      $data = array_keys($paths);
+      $expire = REQUEST_TIME + (60 * 60 * 24);
+      cache_set($cid, $data, 'cache_path', $expire);
+    }
+  }
+}
+
+/**
  * Given an internal Drupal path, return the alias set by the administrator.
  *
  * @param $path
@@ -241,3 +300,45 @@
   }
   return preg_match($regexps[$patterns], $path);
 }
+
+/**
+ * Central static variable storage.
+ *
+ * @param $name
+ *   Globally unique name for the variable. For a function with only one static,
+ *   variable, the function name (e.g. via the PHP magic __FUNCTION__ constant)
+ *   is recommended. For a function with multiple static variables add a
+ *   distinguishing suffix to the function name for each one.
+ * @param $default_value
+ *   Optional default value.
+ * @param $reset
+ *   TRUE to reset a specific named variable, or all variables if $name is NULL.
+ *   Resetting every variable should only be used, for example, for running
+ *   unit tests with a clean environment. Should be used only though via
+ *   function drupal_static_reset().
+ *
+ * @return
+ *   Returns a variable by reference if $reset is FALSE.
+ */
+function &drupal_static($name, $default_value = NULL, $reset = FALSE) {
+  static $data = array();
+
+  // Reset a single value, or all values.
+  if ($reset) {
+    if (isset($name)) {
+      unset($data[$name]);
+    }
+    else {
+      $data = array();
+    }
+    // We must return a reference to a variable.
+    $dummy = NULL;
+    return $dummy;
+  }
+
+  if (!isset($data[$name])) {
+    $data[$name] = $default_value;
+  }
+
+  return $data[$name];
+}
diff -urN ./modules/system/system.install ../drupal-6.13-pathcache/modules/system/system.install
--- ./modules/system/system.install	2009-07-01 15:51:56.000000000 -0500
+++ ../drupal-6.13-pathcache/modules/system/system.install	2009-07-14 09:50:46.000000000 -0500
@@ -565,6 +565,8 @@
   $schema['cache_page']['description'] = 'Cache table used to store compressed pages for anonymous users, if page caching is enabled.';
   $schema['cache_menu'] = $schema['cache'];
   $schema['cache_menu']['description'] = 'Cache table for the menu system to store router information as well as generated link trees for various menu/page/user combinations.';
+  $schema['cache_path'] = $schema['cache'];
+  $schema['cache_path']['description'] = 'Cache table for path alias lookup.';
 
   $schema['files'] = array(
     'description' => 'Stores information for uploaded files.',
@@ -2596,6 +2598,16 @@
 
   return $ret;
 }
+ /**
+ * Create the cache_path table.
+ */
+function system_update_6052() {
+  $ret = array();
+  $schema['cache_path'] = drupal_get_schema_unprocessed('system', 'cache');
+  $schema['cache_path']['description'] = t('Cache table used for path alias lookups.');
+  db_create_table($ret, 'cache_path', $schema['cache_path']);
+  return $ret;
+}
 
 /**
  * @} End of "defgroup updates-6.x-extra"