Disabling core block system in Drupal 7 We are using Drupal 7 with context. I have understood that in Drupal 6 the core block system is inefficient in terms of performance. According to this article http://treehouseagency.com/blog/neil-hastings/2010/10/14/context-everywhere in context module (Drupal 6 version) there is a setting to disable the core block system. But in Drupal 7 context module configuration I cannot find this setting.

How can I make sure the core block system doesn't take part in the showing of the blocks? Ideally I would like to block access to admin/structure/block (since I don't want anybody to set blocks via that interface) but allow to access to admin/structure/block/add (since I want to be able to create blocks but show them with context).
The block module is not required by core; just go to mysite.com/admin/modules and disable it, if you don't want to use it in your site.

EDIT to address your updated question. This code should do the trick. It will deny access directly to the blocks admin overview page, but will still allow access to the add block page.

function mymodule_menu_alter(&amp;$items) {
  // Deny access to the blocks overview page.
  $items['admin/structure/block']['access callback'] = FALSE;

  // Explicitly allow access to the block add page
  $items['admin/structure/block/add']['access callback'] = 'user_access';
  $items['admin/structure/block/add']['access arguments'] = array('required permissions');
}